Wednesday, April 30, 2008

Landscape - Magnolia Scale

I recently had a question on the control of Magnolia scale. The following is information on this pest.

The magnolia scale, Neolecanium cornuparvum (Thro), is one of the largest and most conspicuous scale insects known to occur in Delaware. Adult females may reach nearly 1/2-inch in diameter when fully grown. The scale is shiny tan-brown and smooth. As the scales grow, they are often covered with a white mealy wax. This wax is lost at the time that the crawlers emerge.

Plants Attacked

As the name implies, this insect is primarily a pest of various species of magnolia. Saucer, star, lily and cucumbertree magnolias are the most common trees attacked. It has also been reported to feed on Daphne and Virginia creeper.


Magnolia scales have sucking mouthparts and when heavy infestations completely encrust branches, the branches often die. Badly infested branches and twigs are weakened and growth is retarded. Leaves may also be under-developed. Under a continuous and heavy attack trees may be killed. Like most soft scales, the excess plant sap is excreted as a sweet, sticky material called honeydew. The honeydew drips onto the foliage and branches. A dark fungus, called black sooty mold grows on the honeydew which results in the leaves becoming blackened. This greatly detracts from the plant's normal ornamental value. The honeydew also attracts a ants, bees, wasps and flies which feed on it.

Description and Life Cycle

The magnolia scale spends the winter on one to two year old twigs as tiny, dark-colored nymphs. As temperatures warm in the spring, the scales begin to suck sap and have molted once by early May. At this time two distinct forms can be found, males and females. The males remain small, about 1/8-inch, and soon turn a translucent white. Soon after the males turn white, they emerge as tiny, pink to yellow gnat- like insects with two long waxy threads extending from the tip of the abdomen. The females continue to expand and by early June, they have turned a brownish-purple color. This is also the time that they produce excessive amounts of honeydew. By July the females are covered with a powdery, white waxy coating and are turning more of a yellow- tan color. By late July and August the adult females begin to give birth to their young known as crawlers. The tiny, mobile crawlers move around until they find a suitable feeding site on which they settle down, feed, and remain through the winter.

Control Hints

Though there are several predators and parasites known that attack this scale, they rarely do an effective job of control, especially on smaller magnolias.

Strategy 1: Obtain Pest Free Plants - Most of the magnolia scale infestations come with the plants, so carefully inspect the branches of plants being considered for purchase. The large scale exoskeletons often remain from the previous season. Any plants with these remains should be avoided.

Strategy 2: Summer and Dormant Oils - Horticultural oils (often called summer oils) at 1.5-2.0% applied after the crawlers have settled in late August can be very effective in reducing the scale population. Be sure to thoroughly wet down the stems and leaves. Dormant oils can be applied in October to November and again in March to kill the overwintering nymphs located on the stems. Be sure to check the spring buds as some damage may be caused on the flower buds if they have begun to swell.

Strategy 3: Standard Chemical Control - Magnolia scale can be satisfactorily controlled with a variety of insecticides if applied when the insects are in the freshly settled crawler stage. This is usually in late August to early September. Sprays applied before the crawlers are present, or after they have become dormant in the overwintering stage will have little effect. Some arborists have used Merit (imidacloprid) soil drenches each April or May with spotty records of success. The imidacloprid drenches will probably take two years before being effective, and not even that is guaranteed. Meanwhile, spraying is the only remaining option (other than replacing the trees). Talstar has been effective on most of the soft scale insects, but in this case, you will probably need two applications two weeks apart starting at this time to make a good dent in the infestation. Some of the new neonicotinoid insecticides have been very effective on soft scales and mealybugs. You may want to try foliar sprays of Flagship, Safari, or Tristar for Magnolia scale in the crawler stage or as soil drenches for systemic control when in stationary stage.

Magnolia Scale. Photo by John A. Weidhass, Virginia Polytechnic Institute and State University,

Taken largely from "Magnolia Scale And Its Control" by J. Shetlar. This is an Ohio State University Extension Fact Sheet, Entomology.

Greenhouse, Nursery, and Landscape - Glyphosate Can Have Root Activity Under Certain Conditions

There have recently been some problems with potential glyphosate (Roundup, many others) herbicide contaminating some planting containers. We normally think of glyphosate as a herbicide with no root activity because it is inactivated in soils. However, this is not always the case. Glyphosate has some potential to be taken up by plant roots in very sandy soils, container media (soilless mixes), and organic soils. Caution must be taken in these conditions.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County

Tuesday, April 29, 2008

Landscape and Turf - Liquid Lime

There is a considerable amount of liquid lime that is sold to the landscape and turf industries, especially for hydroseeding. Liquid lime is a tool to get a quick pH response at sites. However, it should not take the place of regular liming programs. The following is information on liquid lime.

Lime is sometimes sold as a suspension, often called “liquid lime.” It consists of fine lime particles mixed with water and a suspending clay. All the lime particles must be 100 mesh or finer. Up to 1,000 pounds of lime can be suspended in a ton of liquid product. The main advantages of liquid lime are ease of handling and precise application. This material, although a fluid, does not react any faster or differently than dry lime of the same particle size. All of the lime in a suspension is fast acting, and a ton of product (1,000 pounds of fine lime particles plus clay and water) will raise the pH as fast as a ton of dry lime. However, due to particle size and enhanced initial reactivity, the effectiveness of suspensions is short-lived, compared to regular agricultural limestone, and liming will probably have to be repeated every year. There also may be some potential for raising soil pH slightly above the target for a period of time if these materials are used. With liquid lime the initial pH spikes are higher but pH drops occur more quickly and to a greater degree. In the end, using suspensions to correct soil acidity is considerably more expensive.

Taken in part from a North Carolina State University Soil Facts publication on Soil Acidity and Liming.

Turf, Landscape, Greenhouse, and Nursery - Be Cautious When Evaluating New Products With Plant Growth or Plant Health Promoting Claims

Each year new products are offered in the trade that promise miraculous responses when used on plants. Professionals should be cautious when being offered products that seem to be "too good to be true". I came across a good article on this subject from Rutgers University.

There are many products out there and new ones emerging all the time that make claims to “bolster plant health”, “control diseases” (like Phytophthora and Pythium), and cure many woes with plants. With the difficulty in controlling devastating diseases like Phytophthora and the high prices of alternative control methods it is tempting to try new products.

Unfortunately, many of the new products available have not been tested by university researchers and do not have the non-biased, replicated, scientific studies to back up the claims being presented to growers to entice purchasing these products. The reason for lack of university research is often due to the fact that companies producing these products do not have the funds to support the type of research needed to verify the product’s success. Generally, they are small, up-starting companies who may or may not have a good product. They may have done their own studies or have done studies with growers who have had success, but often what works on one location, may not universally work for others.

There are so many factors, like soil type, water quality, environment, pH, crop variety, etc., that influence the success or failure of a product. Additionally, some of the products sold have inconsistent attributes, like fertility level, pH, contaminants, etc. They may have interactions with other products. Take for instance a transplant mix enhancer/amendment that is made from a compost product. Composts are often inconsistent. Composts are mostly made from products like plant materials, wood by-products, manures, and other organic materials. When you mix an enhancing product with a transplant mix there is more chance of seeing an affect than if used in the field. Why? In the greenhouse using trays with small cells or even in pots, there is less growing media to interact with the plant. So the affect will be seen more dramatically then when plants are in the field with a greater amount of soil for growth and development. Some enhancing or amendment products have shown little or no affect on plant growth. Others have induced nutrient deficiencies, especially in young transplants.

Your best bet is to proceed with caution when trying a new product that has claims to improve plant health or control diseases. Try it if you think it may help. However, try it on a small scale. Don’t make a drastic change based on a good sales pitch. Always ask for a nutrient analysis (if it has fertility claims) and an ingredients list and label for the product. You can consult your county horticultural agent, but chances are many of these products do not have scientific data to back up claims. When looking into these products ask the manufacturer or sales person to show you university data from research by cooperative extension. If they have none, see if they are willing to fund a project for university studies to prove the product is reliable and meets the claims being presented.

This article is not meant to promote or discourage the use of new plant or soil enhancing products, it is just mean to bring awareness to professionals about how to proceed in investigating new products.

Adapted from "Plant or Soil Enhancing Products: Proceed with Caution" by Michelle Casella, Agricultural Agent, Rutgers Cooperative Extension of Gloucester County in the April 19, 2007 edition of the Plant and Pest Advisory, Landscape, Nursery, and Turf Edition.

Monday, April 28, 2008

Landscape - Vetch as a Weed of Landscape Beds

The following is an article on vetch and its control in landscape beds.

Vetch can be a problem weed in landscape beds in the spring. There are several species of these leguminous winter annuals that grow profusely in April-May, flower, reseed and die out in the summer heat. These seeds will germinate in the late summer/fall. Growth regulator herbicides do a good job of controlling vetch in turf but cannot be used in landscape beds in most cases. One exception is clopyralid (Lontrel) that can be used on certain evergreen species for vetch control (check the label for more information). A second option is August applications of preemergence herbicides such as Snapshot or Gallery to stop fall germination; however results have been variable. Shielded postemergence spot treatments with glyphosate, pelargonic acid, or glufosinate are effective in the fall on small plants but may not be in the spring. In some severe infestations you may need to renovate beds and replace the mulch.

Vetch Infestation in a Ground Cover Bed.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Pictures from the UDBC

The following are some pictures I took recently at the University of Delaware Botanic Gardens.

Service Viburnum
Burkwood Viburnum
Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Sunday, April 27, 2008

Turfgrass - Tenacity Herbicide Currently Only Labeled for Golf Courses and Turf Farms

There has been considerable interest in mesotrione as a turfgrass herbicide because of its wide and unique weed spectrum. While it has received registration as Tenacity, it is currently only labeled for golf courses and sod farms. If additional labels are received or the label is expanded, we will inform you. You can acces the current label through the Syngenta web site at

Gordon Johnson, Extension Horticulture Agent, UD

Nursery and Landscape - Leafminers to Watch For

The following is a report of two leafminers to watch for in the nursery and in landscapes from the University of Maryland.

Hawthorn Leafminer, (Profenusa Canadensis) and Birch Leafminer (Fenusa pusilla).

The red buds and serviceberry are in full bloom in central Maryland this week and we can expect two species of sawflies to emerge in the next week or so. We will see activity from adult hawthorn leafminers (P. canadensis) and the birch leafminers (F. pusila). The larvae of both species overwinter in the soil as pupae. When the two aforementioned trees are in full bloom the adults emerge from the ground. The adult females will cut a slit into the foliage and lay eggs between the leaf surfaces. The larvae feed in blotch mines between the leaf surfaces. We will see the splotchlike leaf mines show up in late May to June. There are multiple generations of both of these pests each summer.

Control: Soil applications of systemic such as imidacloprid (30 -60 days before leafmining activity. Dinotefuran (Safari) is reported to be uptaken much faster then imidacloprid.

Hawthorn leafminer damage. Photo from Whitney Cranshaw, Colorado State University,

Birch leafminer damage. Photo by Whitney Cranshaw, Colorado State University,

Reprinted from the April 25, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension. Go to for the full report.

Landscape - Stop Mulch Mounding

The following is a short article on the problems with mulch mounding from Susan Barton, Extension Horticulture Specialist, University of Delaware.

I know this is like preaching to the choir, but since I have defined one measure of success in my Cooperative Extension career as the elimination of mulch mounds, I want to leave no stone unturned and no audience unassailed. So, if your company participates in the heaping on of mulch around the base of trees in the spring--get them to stop! If you know people who participate in this practice-- spread the word that mulch mounds harm trees. Moist mulch piled up against the trunk of a tree will cause decay that provide a perfect environment for the development of disease or insect infestation. All you need is a thin layer of mulch to prevent light from reaching the soil and prevent germination of annual weed seeds. Perennial weeds will grow up through even a thick layer of mulch. Mulch should be applied to a depth of 2-3 inches and no deeper! Do your part to educate the uneducated on this mulch issue!

Improper mulch mounding around a tree. Photo from Cornell University Department of Horticulture.

Saturday, April 26, 2008

UDBG Plant Sale Descriptions

I had fun with the recent feature of plants being offered at the UDBG spring plant sale. The written descriptions were taked directly from the Spring Plant Sale catalog. I encourage landscapers and nurserymen to visit the UDBG website and print off this catalog as a reference. We also ecourage all of you to support the University of Delaware Botanic Gardens. This is a great resource for the horticulture industry in Delaware, providing ideas and information on planting materials adapted for Delaware, new and different planting materials, sources of planting materials, and the expertise of UD faculty such as Dr John Frett who can assist you with ideas for business.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County

Turf - Grass Mowing Season is in Full Gear

Grass mowing season is in full gear now. The following are some critical points to consider for professionals that cut grass.
  1. Keep your mower blades sharp. Dull mowers cause excessive damage to grass blades and provide perfect conditions for disease development.
  2. Watch your cutting speed. In an effort to cut as much as quickly as possible, often machines are operated at speeds that do not allow for proper grass cutting. It also causes excessive damage to grass blades (by skimming over blades and cutting at an angle) again setting up for more potential disease pressure.
  3. Do not mow when wet. Wait until the dew is off. You have much more potential to spread disease in wet turf.
  4. Clean mowers between properties,or after passing through weedy sections. Many weeds are in seed now in turf (such as dandelion). You will spread these weed seeds on your mower if you do not clean it off.
  5. Mow at the proper height and do not remove too much leaf area. In the spring, cut cool season turfgrasses higher than your would in the summer. Do not remove more that 1/3 of the leaf blade at any time. Mow to a height between 2-3 inches (lower side for bluegrass, higher side for fescue).

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Friday, April 25, 2008

Nursery and Landscape - Plants to Consider for Delaware Landscapes Featured at the UDBG Plant Sale (Tomorrow!)

This is continuation of the series on plants to consider for Delaware Landscapes featuring those plants that are being offered at the UDBG Spring Plant Sale. The plant sale is tomorrow!

Cornus kousa ‘Big Apple’. Kousa Dogwood 20-30'. Introduced by the Polly Hill Arboretum, ‘Big Apple’ is an appropriate name in several ways. The fruit are exceptionally large, up to 1½ in., and the white bracts measure 5 to 6 in. across. The colorful exfoliating bark and excellent red fall color are similar to the species.

Magnolia (salicifolia × kobus) ‘Iufer’. Magnolia 20'. The magnificent pyramidal habit is seldom seen in American gardens. ‘Iufer’ offers starry white flowers borne abundantly in spring but differs from the species by virtue of the dramatic,
red-tipped anthers.

Magnolia sprengeri ‘Diva’. Magnolia 30-50'. The erect, 8 in. wide, rosy-pink flowers create a refined floral display in early spring. Considered precocious (blooms at a young age), ‘Diva’ is a prolific bloomer.

Cornus sanguinea ‘Cato’. Artic Sun™ Dogwood 3-4'. A must-have for the winter garden, the eruption of color from yellow, to orange, and red is reminiscent of the rising sun. The white flowers in the late spring/early summer, compact habit, and cultural adaptability makes this plant a winner.

For more information go to the online UDBC Spring Plant Sale catalog at

Turfgrass - Red Thread Disease

The following is information on Red Thread disease in turf from Rutgers University.

Red Thread disease, caused by the fungus Laetisaria fuciformis, will be showing up in the near future on susceptible turf. Infections are characterized by the appearance of short red threads (1/16-1/4”) long emerging from tan-colored leaf blades. Affected patches are typically pink in color and range from 1 to 6 inches in diameter. Although perennial ryegrass and fine fescue are most susceptible, Kentucky bluegrass and tall fescue may also be affected. Red thread is typically found on “hungry” (low fertility) turf during cool, wet weather. Well-fertilized turf, however, may also be attacked. To obtain optimum disease control, maintain adequate fertility levels, avoid drought stress and excessive thatch, and apply Banner, Bayleton, Chipco 26GT*, Compass, Curalan*, Eagle, Headway, Heritage, Insignia, ProStar, Rubigan, Tartan or Touche per manufacturer’s recommendations (*not for use on residential properties).

Photo from the University of Wisconsin, Madison plant pathology.

Reprinted from the May 3, 2007 edition of the Plant and Pest Advisory; Landscape, Turf, and Nursery edition, Rutgers Cooperative Extension and New Jersey Agricultural Experiment Station.

Thursday, April 24, 2008

Nursery and Landscape - Plants to Consider for Delaware Landscapes Featured at the Upcoming UDBG Plant Sale

This is continuation of the series on plants to consider for Delaware Landscapes featuring those plants that are being offered at the upcoming UDBG Spring Plant Sale.

Hakonechloa macra ‘All Gold’. Golden Hakone Grass 1.5' Dramatic cascading ribbons of metallic foliage that look brightest with morning sun. Slightly more upright than other cultivars. Looks wonderful combined with blue-foliaged hostas. Hard to find in the trade, use it to illuminate the border, container or oriental garden.

Gladiolus ‘Boone’. Sword Lily 5'. Unusual, remarkably hardy (zone 6) heirloom cultivar. Small jewel-like, soft pastel apricot flowers open over an extended period of time on multiple flower stems that never need staking. This connoisseurs’ plant will produce many new corms in a couple years. Exquisite; mixes with just about everything.

Gentiana asclepiadea. Willow Gentian 1'. Gorgeous trumpet-shaped blue flowers adorn erect stems in August. Highly sought after plant for the cool season garden. Especially attractive in combination with Athyrium felix femina ‘Lady in Red’ and Dryopteris erythrosora.

Baptisia australis ‘Sky Blue’. Blue False Indigo 3-4'. UDBG introduction selected for bicolored blooms with white/pale blue upper petals and blue lower petals. Colors intensify as flowers mature. Striking new cultivar; excellent as a specimen plant or in small groups. Not found in the trade.

For more information go to the online UDBC Spring Plant Sale catalog at

Landscape and Nursery - Rusts on Junipers

The following is information on two common rusts that affect Junipers in Delaware.

CEDAR-QUINCE RUST caused by the fungus Gymnosporangium clavipes. The orange-red swellings on the twigs will be very evident. This fungus infects groundcover junipers, Juniperus horizontalis, Juniperus scopulorum, and several others as well. On this host the swellings are often undetected and can persist for years. The galls are perennial on juniper and should be pruned out if possible. The alternate host is hawthorn, serviceberry, and several other rosaceous plants and causes deformed fruit and green twig dieback.

Cedar-quince rust on Juniper. Photo from the University of Massachusetts Extension.

CEDAR-APPLE RUST. Be on the lookout as well for the round woody galls on twigs and branches of eastern red cedar, Juniperus virginiana. During wet weather orange-red spore horns emerge. These gelatinous appendages produce the spores that infect apple and crabapple leaves at this time of the year. The best control on cedar is to prune out the galls to the extent that is practical. These cedar-apple rust galls can be pretty spectacular for fungi-philes.

Cedar-apple rust on juniper. Photo from the University of Nebraska, Lincoln, Plant Pathology

Information from Bob Mulrooney, Extension Plant Pathologist, UD.

Wednesday, April 23, 2008

Landscape and Nursery - Scale Pests of Leyland Cypress, Arborvitae, Cryptomeria, and Junipers

There are two scale insects showing up on Leyland Cypress, Arborvitae, Cryptomeria, and Junipers called the Maskell scale and the minute cypress scale. The following is information on these pests from the University of Maryland.

If you are growing Leyland Cypress, Arborvitae, Cryptomeria, or Junipers at your nursery or your customers have these plants in their landscapes you need to look carefully for Maskell scale and minute cypress scale on the foliage.

We have received samples from a number of sites in the last couple of weeks with Maskell scale. This armored scale appears to be showing up more frequently on Leyland cypress and Cryptomeria. We have also received samples of Leyland cypress from several sites with minute cypress scale present in abundant numbers. In some cases Maskell scale and minute cypress scale have been found on the same plants. In 1991, Hodgson and Hilburn reported Bermuda cedar that was infested with both Maskell scale and minute cypress scale killed entire trees and almost eliminated the Bermuda cedar on Bermuda.

There is concern with the increase in frequency of samples in Maryland infested with Maskell scale and minute cypress scale. We do not have much information on these pests and the exact number of generations per year is not clear for Maskell scale. Davidson and Miller (2006) reported that in Maryland, adult males are present in late September into October along with all stages including eggs, crawlers, 2nd instar and adult females. If you have infested plants please let us know when you see crawlers so we can alert others in the state.

Minute Cypress Scale on Arborvitae

Maskell Scale on Cryptomeria

Information adapted from the April 18, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension

Greenhouse - Shore Flies vs Fungus Gnats

Greenhouse growers sometimes have a hard time telling shore flies, a nuisance pest, from fungus gnats that can damage plants. The following is a short article on the subject from the University of Maryland.

We are receiving a lot of reports from greenhouses and garden centers that shore fly adults are all over the foliage of their plants, especially on zinnias, begonias, and osteospermum. We just went through two weeks of cool, rainy weather which is ideal for algae growth. Algae is what the larval stage of shore flies feed and thrive on, resulting in the increase of adult populations that we are seeing this week. Growers often have a hard time telling shoreflies apart from fungus gnats on their sticky cards. Shoreflies are nuisance pests, but fungus gnats damage plants by feeding on the roots and tunneling into the stems. Some ways you can tell them apart are that fungus gnats have slender bodies, a Y-shaped pattern on their wings, and the larvae have a black head capsule. Shorefly adults have more robust bodies, 5 white spots on their wings, and Note the 5 spots on the wings the larvae lack a black head capsule.

Reprinted from the April 18, 2008 edition of the Greenhouse TPM/IPM Weekly Report from the University of Maryland Cooperative Extension

Tuesday, April 22, 2008

Turfgrass - White Clover Control

I have recently had questions about controlling white clover in lawns. The following is information on this pasture legume that can become a weed problem in turf.

White Clover is a low growing sloloniferous legume that often infests cool season turfgrass. Although not unattractive, it is viewed a weed because it is short lived and seed heads attract bees. Identify by the compound leaves composed of 3 unstalked leaflets less than 1 inch long with white crescent shaped marks. Blooms will be 1 inch diameter white balls starting to appear in May and producing seeds that can last for many years in the soil. White clover is most prevalent in turf receiving limited nitrogen fertilization and is more of a weed problem in cool, moist years. Low mowing also favors white clover.

Control white clover in cool season turf by increasing nitrogen fertilization, cutting higher, and managing for a dense grass stand. Many broadleaf herbicides are effective on white clover including products containing triclopyr (Turflon ester, Confront, other combinations); clopyralid (Lontrel, Confront; clopyralid is not for use in residential turf); quinclorac (Drive – can also be used on new seedings), fluroxypyr (Spotlight, Escalade ), and combination broadleaf products that contain mixtures of 2,4-D, dicamba, MCPP, or MCPA (Trimec and many others; note that any of these ingredients alone will not provide adequate control). Newer combination products such as Q-4, Speedzone, and Powerzone will also control clover.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Turfgrass - Orchardgrass as a Weed in Turf

Orchardgrass is a pasture and hay grass that can be a problem weed in turf type tall fescue and Kentucky bluegrass. Recently I posted control measures for this grass. The following are pictures of orchardgrass.

Orchardgrass clumps. Note the blue-green color.

Orchardgrass with seed head.

Orchardgrass has distinct flattened stems.

Photos by Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Monday, April 21, 2008

Nursery and Landscape - Plants to Consider for Delaware Landscapes Featured at the Upcoming UDBG Plant Sale

This is continuation of the series on plants to consider for Delaware Landscapes featuring those plants that are being offered at the upcoming UDBG Spring Plant Sale.

Edgeworthia papyrifera. Paperbush 3-5'. The dark blue-green leaves and distinctive branching add a tropical feel to the garden. Subtle, pendulous clusters of golden yellow flowers appear in early spring. Provide protection in the winter as plants are damaged in the single digit temperatures.

Forsythia viridissima ‘Bronxensis’. Bronx Green Forsythia 1-1.5'. Arguably the ideal forsythia, growing only 12 in. tall and spreading 2 to 3 ft. across, and no pruning necessary to keep in check. A good groundcover for sunny spots, the bright green
stems are packed with primrose-yellow flowers in the early spring.

Hydrangea quercifolia ‘Snowflake’. Oakleaf Hydrangea 5-8'. The abundance of sterile white flowers and doubling of the petals creates an impressive display that start in the summer and continues well into fall. Added to the burgundy fall color, this is a
dramatic plant offering multiple seasons of interest in the garden.

Hypericum kalmianum ‘Cfflpc-1’. Blue Velvet™ St. John's-Wort 2-3'. Striking blue foliage provides perfect backdrop for the bright yellow summer flowers, followed
by red fruit. It is great planted in masses or mixed with perennials.

For more information go to the online UDBC Spring Plant Sale catalog at

Landscape and Nursery - Drought Tolerant Small Trees

We continue to have a dry spring this year and coming off the drought of 2007 our subsoil moisture is very low. Landscapers and nurserymen should consider plants that are more drought tolerant. The following are some drought tolerant small trees for Delaware.

Many small trees are understory trees that provide an excellent transition planting between natural and more refined areas of a property. Small trees used as specimen trees should have many seasons of beauty, such as flower display, foliage effects, fall color, fruit and bark or habit interest.

Acer ginnala, Amur Maple, 15 to 18 feet; full sun to light shade. Assets: Small tree of rounded outline with lustrous, dark green leaves. ID: Leaves are doubly-serrate and 3-lobed with the middle lobe much longer than the lateral lobes. Use: Small specimen, patio, screen, grouping and massing tree.

Crataegus phaenopyrum, Washington Hawthorn, 25 to 30 feet. Assets: A broadly oval tree with reddish-purple new foliage that changes to lustrous dark green, orange to scarlet fall foliage, white flower clusters and glossy red fruit. ID: Small, sharply serrate, 3 to 5-lobed leaves. Use: Excellent single specimen tree or screen.

Koelreuteria paniculata, Goldenraintree, 30 to 40 feet; full sun. Assets: Beautiful dense tree of regular rounded outline with large yellow flower cluster borne in late June to early July. Fruit are large, papery lantern-like capsules. ID: Pinnate or bipinnately compound leaves with coarsely serrate leaflets. Use: Excellent small lawn tree, specimen or patio tree.

Syringa reticulata, Japanese Tree Lilac, 20 to 30 feet; full sun and requires well-limed soil. Assets: White, fragrant flowers in large terminal clusters are extremely showy. Dark green leaves and cherry-like, reddish-brown bark with horizontal lenticels. Use: Excellent trouble-free lilac makes a good specimen or street tree.

Viburnum prunifolium, Blackhaw Viburnum, 12 to 15 feet; sun or shade. Assets: Round-headed small tree with creamy, flat-topped flowers and bluish-black fruit. ID: Dark green leaves with a stiffly branched growth habit. Use: Interesting as a small specimen tree or in groups.

Excerpted from "Plant Selection for Water Conservation" by Dr. Susan Barton, UD Extension Ornamental Horticulture Specialist.

Sunday, April 20, 2008

Nursery and Landscape - Plants to Consider for Delaware Landscapes Featured at the Upcoming UDBG Plant Sale

This is continuation of the series on plants to consider for Delaware Landscapes featuring those plants that are being offered at the upcoming UDBG Spring Plant Sale.

Ginkgo biloba ‘Golden Globe’. Ginkgo 60'. Selected for its broad, rounded habit and clear yellow fall color, this male clone does not yieldthe odiferous fruits possible when buying seedling-grown trees.

Aucuba japonica ‘Longifolia’. Japanese Aucuba 4-6' Unlike the typical cultivars, this cultivar has solid dark green foliage. Evergreen with long slender foliage that adds textural contrast in a shrub border or foundation planting. The UDBG plant has survived -7 F with minor defoliation.

Berberis × gladwynensis ‘William Penn’. Barberry 4'. Dense and mounded, this low shrub's best feature is its dark green foliage that turns bronze in the winter. Dark yellow flowers add interest in the spring.

Buxus microphylla ‘Faulkner’. Boxwood 2-3'. Well behaved evergreen shrubs are difficult to find. ‘Faulkner’ is ideally suited for use as a compact hedge or in a tight corner due to its small habit.

Callicarpa dichotoma var. albifructus ‘Duet’. White Beautyberry 4-6'. A real showstopper in the fall when delicate stems are laden with fruit! The white variegation in the leaves only further underscores the show. The bold color is great in the summer to fall mixed border.

For more information go to the online UDBC Spring Plant Sale catalog at

Landscape and Nursery - Drought Tolerant Shrubs

We continue to have a dry spring this year and coming off the drought of 2007 our subsoil moisture is very low. Landscapers and nurserymen should consider plants that are more drought tolerant. The following are some drought tolerant shrubs for Delaware.

Shrubs are used in the landscape to provide transition between tall vertical trees and the horizontal plane of the ground. Shrubs are chosen for habit, foliage, flower or fruit attributes. The most useful shrubs have more than one season of interest. If bright blossoms are the only attribute, the plant should be tucked away so it doesn't detract from the landscape once the flowers are gone. Many of the traditional spring-blooming flowering shrubs such as forsythia, spirea, lilac and weigelia are somewhat drought-tolerant.

The following shrubs are considered drought-tolerant.

Aronia arbutifolia, Red Chokeberry, 6 to 10 feet; full sun or half shade. Assets: Bright red fruits are born in great abundance along the stems. ID: Upright multistemmed shrub with even, black-tipped teeth along the leaf margins. Use: Best in masses.

Chaenomeles speciosa, Common Floweringquince, 6 to 10 feet; full sun or partial shade. Assets: Flowers which range in color from orange through scarlet to white. ID: Leaves have large conspicuous stipules at the petiole base. Use: Effective as a hedge or in a shrub border but has a very short period of interest.

Cornus racemosa, Grey Dogwood, 10 to 15 feet; full shade or sun. Assets: Multistemmed shrub that forms a thicket. Grey older wood and light, reddish-brown younger stems compliment each other well. Pinkish-red inflorescences are effective into December. ID: Leaves with typical dogwood venation and a dull grey-green color. Use: Best naturalized in masses and used for its winter character.

Elaeagnus pungens, Thorny Elaeagnus, 10 to 15 feet, sun or shade. Assets: Fragrant, small white flowers and somewhat evergreen leaves flecked with silver. ID: Leaves have ruffled margins and the undersides are covered with silver scales. Use: Good for banks, hedges, screens and natural barriers. Must be pruned to attain a desirable habit.

Myrica pensylanica, Northern Bayberry, 5 to 12 feet; full sun to half shade. Assets: Semi-evergreen leaves are aromatic when bruised. Greyish-white berries cover the stems of female.
plants from September to the following April. ID: Obovate leaves have a leathery texture. Use: Excellent in masses or as part of a border; good salt tolerance.

Pinus mugo var. mugo, Mugo Pine, less than 8 feet tall; sun or partial shade. Assets: Prostrate evergreen shrub with medium green needles. ID: Rigid needles in bundles of two. Use: A low evergreen shrub for foundations, masses or groupings.

Potentilla fruiticosa, Bush Cinquefoil, 1 to 4 feet; full sun to partial shade. Assets: Dainty clean foliage and yellow flowers that bloom from June through frost. ID: Pinnately compound leaves are dark green and somewhat silky. Use: Good plant for the shrub border, massing, edging or as a facer plant in a foundation. Adds color to the landscape and many cultivars are available (some with white flowers).

Pyracantha coccinea, Scarlet Firethorn, 6 to 18 feet; full sun to partial shade. Assets: Semi-evergreen shrub with flowers that shroud the plant in white. Orange-red fruit can be spectacular. ID: Pyracantha have stiff thorny branches with spines along the stems. Use: Makes a good informal hedge, barrier plant or espalier.

Rhus typhina, Staghorn Sumac, 15 to 25 feet, half to three-quarters shade or full sun. Assets: Nice leaf texture and spectacular yellow, orange and scarlet fall color. ID: Pinnately compound leaves have 13 to 27 leaflets. Stems are densely covered with velvety hair. Use: Naturalize or use in masses. Can be invasive as it suckers freely from the roots.

Viburnum lentago, Nannyberry Viburnum, 15 to 18 feet; sun or shade. Assets: Creamy yellow flowers and a bluish-black fruit are borne on this large shrub with slender arching branches. ID: Dark green, finely toothed leaves have winged petioles. Use: Ideal shrub for naturalizing; works well as a background or screen plant.

Vitex agnus-castus, Chastetree, 8 to 10 feet; full sun. Assets: Flowers are lilac, fragrant and occur from June through September. ID: Palmate leaves are greyish-green. Use: Interesting foliage texture and late-season flowers make a good addition to the shrub border.

Excerpted from "Plant Selection for Water Conservation" by Dr. Susan Barton, UD Extension Ornamental Horticulture Specialist.

Saturday, April 19, 2008

Nursery and Landscape - Plants to Consider for Delaware Landscapes Featured at the Upcoming UDBG Plant Sale

This is continuation of the series on plants to consider for Delaware Landscapes featuring those plants that are being offered at the upcoming UDBG Spring Plant Sale.

Salvia nemorosa ‘Haeumanarc’. Marcus® Meadow Sage 8-10". This low-growing, long-blooming cultivar is ideal for the front of the border. Spikes of striking, deep purple flowers from summer through fall attract butterflies and bees. Remove spent blooms to extend the bloom season.

Verbena hastata. Blue Vervain 2-6'. Numerous, candle-like spikes of tiny purple-blue flowers grace the garden from early summer.through fall. Well-loved for wildflower plantings; attracts butterflies.

Vernonia glauca. Broadleaf Ironweed 3-5'. Though endangered in both Pennsylvania and New Jersey, this wildflower is a breeze to grow in the garden. Perfect for meadow plantings or massed at the back of a border, its deep purple, wispy flower clusters on stout stems provide late summer/early fall interest.

Viola ‘Etain’. Violet 6-8" Highly scented, extra large flowers are held erect on this clump-forming violet. Lavender edges adorn both the deep yellow, orange-eyed lower petals and the pale yellow upper petals. Flowers profusely late spring/early summer and sporadically into fall.

For more information go to the online UDBC Spring Plant Sale catalog at

Landscape and Nursery - Drought Tolerant Groundcovers

We have had a relatively dry Spring this year and coming off the drought of 2007 our subsoil moisture is very low. Landscapers and nurserymen should consider plants that are more drought tolerant. The following are some drought tolerant groundcovers.

Drought Tolerant Groundcovers

The use of any groundcover will help to stabilize the soil, reduce weeds and conserve water. Most groundcovers are less water demanding than turf. The following are groundcovers that are particularly drought-tolerant.

Aegopodium podagraria "Variegatum", Bishop's Goutweed, 8 to 10 inches; sun or shade. Assets: Light green leaves with white margins. ID: A herbaceous plant with compound leaflets that are divided into threes. Use: This spreading groundcover can become invasive when used with other plants.

Arctostaphylos uva-ursi, Bearberry, 6 to 12 inches; full sun to part shade. Assets: Low-growing, glossy leaved, evergreen groundcover with leaves that turn reddish in the fall. Small, white, urn-shaped flowers appear in late April to May. Bright red fruit is effective from late July through August. ID: Small obovate leaves. Use: One of the prettiest, sturdiest and most reliable groundcovers.

Cerastium tomentosum, Snow-in-Summer, 6 inches; full sun. Assets: White flowers cover the silver leaves in May and June. ID: Small linear leaves of this mat-forming herbaceous perennial are covered with white woolly hair. Use: Groundcover or edging plant.

Cotoneaster dammeri, Bearberry Cotoneaster, 1 to 1 1/2 feet. Assets: Dark green foliage is semi-evergreen. Red berries are sparsely produced. ID: Low, prostrate shrub with small leaves. Use: Excellent groundcover for banks, gentle slopes, masses, shrub borders or foundations.

Hemerocallis sp., Daylily, 1 1/2 to 4 feet; full sun or partial shade. Assets: Trumpet-shaped flowers can be found in almost any color of the rainbow. ID: Long linear leaves appear in clumps and tall flowering stems extend from the center. Use: When used in masses, daylilies make a good herbaceous groundcover.

Hypericum calycinum, Aaronsbeard St. Johnswort, 1 to 1 1/2 feet; full sun to partial shade. Assets: Bight yellow flowers bloom from June through September. ID: This semi-evergreen shrub has ascending stems with dark green leaves. Use: Hypericum makes a good groundcover because it grows quickly and effectively covers an area in a short amount of time. Mow to the ground to induce new growth each spring.

Juniperus horizontalis, Creeping Juniper, 1 to 2 feet; full sun. Assets: Low-growing shrub that forms a large mat. Foliage may be steel-blue turning plum purple in winter. ID: Most of the leaves are scale-like. Use: This extremely tolerant groundcover has many cultivars with varying habits and foliage colors.

Sedum sp., Stonecrop, 2 inches to 2 feet; full sun. Assets: Succulent green leaves and small yellow, white or pink flowers that are borne in showy flower clusters. ID: Fleshy leaves with shapes that vary between species. Use: Most sedums are mat-forming groundcovers. A number of different species are available.

Santolina chamaecyparissus, Lavender Cotton, 1 1/2 to 2 feet; full sun. Assets: This broad spreading herbaceous perennial has silver-grey, fine-textured foliage and button-like yellow flowers. ID: The pubescent leaves are pinnately divided into very small segments. Use: Santolina can be used in the rock garden, as a low hedge or as a groundcover.

Thymus serpyllum, Creeping Thyme, 3 to 6 inches tall; full sun. Assets: This mat-forming herbaceous perennial has greyish-green leaves and small, fragrant, purple flowers. ID: The small leaves have a strong mint-like odor. Use: Thyme makes an excellent groundcover around walks where the aroma is released when it is inadvertently crushed.

Excerpted from "Plant Selection for Water Conservation" by Dr. Susan Barton, UD Extension Ornamental Horticulture Specialist.

Friday, April 18, 2008

Landscape and Nursery - Crabapple Scab

Consider fungicide applications for control of crabapple scab on susceptible varities. The following is an article on the subject.

CRABAPPLES are pushing new growth now, some are approaching bloom, if very good control is needed on susceptible crabapples now is the time to begin fungicide applications for crabapple scab. Commercial applicators can apply Banner Maxx, Systhane, Daconil 2787, Cleary's 3336 (thiophanate-methyl), or any of the mancozeb fungicides beginning now at 7-14 day intervals depending on the label directions. Crabapple scab does not kill trees but can defoliate them prematurely if weather conditions favor infection throughout the season. The most effective chemical control is preventative fungicide applications before infection takes place during this time of year. Many landscape situations do not require heavy fungicide use and the use of resistant cultivars is always encouraged.

By Bob Mulrooney, Extension Plant Pathologist, UD

Nursery and Landscape - Plants to Consider for Delaware Landscapes Featured at the Upcoming UDBG Plant Sale

This is continuation of the series on plants to consider for Delaware Landscapes featuring those plants that are being offered at the upcoming UDBG Spring Plant Sale.

Chamaecyparis obtusa 'Nana Gracilis'. Hinoki Falsecypress 6'. The formal, pyramidal habit and slow growth rate make this an ideal conifer for winter interest. Dense, scalloped-shaped, rich green foliage embellishes the winter landscape, whether bedecked in snow or without.

Cryptomeria japonica ‘Elegans Nana’. Japanese Cedar 3-6'. The broad mounded, dwarf habit, combined with the bluish green summer foliage that turns purple in the fall and winter makes this a plant with year-round interest.

Pinus koraiensis. Korean White Pine 30-40'. The blue green foliage and elegant habit of this medium sized pine make it the envy of conifer lovers. The graceful foliage has a soft texture and excellent winter color.

Taxus canadensis. Canadian Yew 3-6'.Rarely seen in commerce, this native yew grows well in shade and makes an excellent groundcover. The habit is more open than most yews. This is an extremely cold hardy species.

For more information go to the online UDBC Spring Plant Sale catalog at

Landscape - Spring Leaf Spots and Blotches

Fungal leaf spots and blotches can occur in susceptible landscape plants in the spring. The following is an article on the subject from the Rutgers Plant and Pest advisory.

What would springtime be without leaf spots? Leaf diseases are caused by a wide variety of fungal and (some) bacterial pathogens. Most ornamental plants are susceptible to one or more of these diseases. For example, one leaf spot that we commonly see in Delaware landscapes is Phyllosticta leaf spot of maple.

The fungi that cause leaf spots and blotch reproduce and spread by means of spores. These spores are produced in fruiting structures in leaf litter on the ground. Once splashed to developing tissue after budbreak, the spores germinate and penetrate the leaf surface. The fungus then grows throughout the leaf, killing the tissue as it goes and leaving spots or blotches that are often accompanied by a yellow halo. Look closely at the lower leaf surface of leaf lesions later in the summer, and you may see the small, dark fruiting structures that serve to produce inoculum the following spring.

Horsechestnut leaf blotch is truly spectacular when it develops following environmental conditions optimal for disease development. Lesions of this fungal disease, caused by Guignardia aesculi, first appear on horsechestnut and buckeye in the spring as watery blotches that turn brown within a few days and are bordered by a yellow band. The blotches coalesce, causing leaflets to distort and curl, and fall prematurely. The disease also affects petioles and fruit. From a distance, severely affected trees appear scorched, so get close and look at the leaves before making a diagnosis.

Since the development of leaf spots and blotch is favored by abundant moisture and cooler temperatures, management benefits from a few basic strategies: reduce leaf wetness and humidity in plantings (e.g., improve air-flow through proper spacing and weed management, irrigate during early morning hours, and avoid overhead watering); remove leaf litter to reduce fungal inoculum; and improve plant vigor to help reduce disease severity. Remember, however, that the environment drives theleaf-spotting process, so expect to see more following wet springs.

Fungicides are effective only if they are present on leaf surfaces at the time the fungi are producing spores. Fungicides applied after leaf lesions are visible are not effective. Most damage caused by the fungi that cause leaf spot and blotch is merely cosmetic, thus the use of fungicides for disease control in the landscape is not usually recommended unless plants are severely stressed. If desired, however, leaf spots may be prevented with foliar applications of azoxystrobin, Benefit, chlorothalonil, ConSyst, copper, iprodione, Junction, mancozeb, maneb, propiconazole, Spectro, Stature, thiophanate-methyl, or Zyban. In general, these preventive fungicides are applied at budbreak and the spray repeated twice at 7- to 14-day intervals. Fungicides labeled for horsechestnut leaf blotch include chlorothalonil, Junction, mancozeb, maneb, Manhandle, Spectro, Stature, or thiophanate-methyl, applied at budbreak and repeated every 7 to 21 days. As always, check individual labels for specific host and application rate recommendations.

Reprinted with minor changes from "Diseases of Landscape Ornamentals in the Springtime (Part I)" by Ann B. Gould, Ph.D., Specialist in Plant Pathology, Rutgers University in the April 3, 2008 edition of the Plant and Pest Advisory; Landscape, Nursery, and Turf Edition.

Wednesday, April 16, 2008

Nursery and Landscape - Plants to Consider for Delaware Landscapes Featured at the Upcoming UDBG Plant Sale

This is continuation of the series on plants to consider for Delaware Landscapes featuring those plants that are being offered at the upcoming UDBG Spring Plant Sale.

Philadelphus × lemoinei ‘Innocence’. Mockorange 6-8'. Mockorange is noted for the sweet fragrance of the flowers and this cultivar is one of the most fragrant. The nearly 2-in. white flowers permeate the garden in spring. Leaves are sporadically variegated with creamy splashes.

Physocarpus opulifolius ‘Nugget’. Ninebark 6-8'. Foliage emerges deep golden in spring, fades to lime green in summer, and turns yellow in fall. Plants produce white flowers in the late spring. Vigorous shrub which tolerates harsh conditions. Attractive bark as it ages.

Pieris japonica ‘Dorothy Wycoff’. Japanese Pieris 4-6'. John Frett's favorite of the Japanese pieris as it is more compact but still a strong grower. The flower petals are white but the sepals are dark red. Your eye blends them into a very lovely

Poncirus trifoliata ‘Flying Dragon’. Contorted Hardy Orange 6-10'. The green stems have prominent twisting thorns offering interest in the winter landscape. White flowers in the spring and small oranges in the fall add interest in other seasons. Birds love to nest in the impenetrable branches. Once planted as a living “wall” to keep intruders off of one's property.

For more information go to the online UDBC Spring Plant Sale catalog at

Landscape - Winged Ants

The following is a short article from the University of Maryland on winged ants in the landscape.

While you are working in customers’ landscapes you might notice a large red colored ant with wings hanging around in mulch beds or near sidewalks. One of the common ants we are getting inquiries about in early April is the citronella ant. They become very active when the temperature warms up and usually right after a rain period. At this time of year they produce winged (alate) male and females. The males are darker colored and about 1/3 to 1/2 the size of the females. The winged females are out and producing pheromones to attract males. The citronella ant is pretty much harmless so you can let your customers know that there is no need
for control.

Reprinted from the April 11, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.

Tuesday, April 15, 2008

Nursery and Landscape - Plants to Consider for Delaware Landscapes Featured at the Upcoming UDBG Plant Sale

This is continuation of the series on plants to consider for Delaware Landscapes featuring those plants that are being offered at the upcoming UDBG Spring Plant Sale.

Fothergilla × intermedia ‘Mt. Airy’. Fothergilla 6'.The best you can ask of any plant is to offer multiple seasons of interest and this one straight out delivers. The fragrant, creamy-white, small bottlebrush-like flower clusters provide a outstanding display in the spring and the superb yellow-orange-red fall color closes the season in the fall. Winter architecture a plus. Plants blend well in the shrub border, as specimens and groups.

Genista lydia ‘Select’. Woadwaxen 1-2'. dd 1 g, Form and flowers meet in this shrub. The low form with arching green branches is as attractive in the winter as it is in the summer. The small leaves accentuate the form in summer. Add the bright yellow flowers in the summer and you have a hit.

Heptacodium miconioides. Seven-son Flower 15-20'. Another shrub with multiple seasons of interest: Soft green leaves, showy, sweetly fragrant, white flowers in summer; red-purple bracts that follow; and attractive scaly bark in winter.
Hibiscus syriacus ‘Antong Two’. Lil’ Kim™ Shrub Althea 3-4'. A stunning new plant selected for its diminutive habit. Flowers are white with a red center and last longer than in most cultivars. The small stature makes this a great combination with perennials or as an accent in mixed shrub plantings.

For more information go to the online UDBC Spring Plant Sale catalog at