Sunday, December 28, 2008

Greenhouse - Impatiens Necrotic Spot Virus INSV

Impatiens Necrotic Spot Virus is one of the most common viruses in greenhouses. It is spread by thrips. The following are lists of plants that are susceptible to this virus.

INSV on Fuschia.

Tables from "Symptoms and management strategies for impatiens necrotic spot virus" by Mary Hausbeck,Plant Pathology in the March 3, 2006 edition of the Michigan State University Greenhouse Alert newsletter.

Saturday, December 27, 2008

Greenhouse - Photoperiod and Flowering

The following is an article on photoperiod effects on flowering from the Michigan State University Greenhouse Alert newsletter.

Photoperiod or day length is the duration of light in a given 24-hour period. Photoperiod naturally varies with latitude and time of year, and many plants, including annuals and perennials, have fine-tuned their flowering to coincide with these seasonal changes in day length. As a result, we can classify plants as being short day, long day or day neutral species.

Short day plants flower when the day length is less than a critical length (often considered to be 12 hours of light or less). Long day plants flower when the day length is greater than a critical length (often considered to be 14 hours or greater). Day neutral plants flower regardless of the day length.

Plants can further be described as having a facultative or obligate photoperiod response. Plants with a facultative response flower faster under a particular photoperiod but will eventually flower under all photoperiods. For example, a facultative short day plant will flower faster under short days but will eventually flower under long days as well (Figure 1). Plants with an obligate response absolutely require a particular photoperiod for flowering. For example, an obligate short day plant will only flower under short days – and never under long days.

Photoperiod manipulation can be achieved in the greenhouse with relative ease. When the day length is long but a short day photoperiod is desired, blackcloth fabric may be pulled over plants in the evening and opened in the morning to provide plants with a short day. This is the same technique used in fall mum production to promote earlier flowering of chrysanthemum when days are naturally long. Growers may utilize existing blackout systems used in fall mum production to provide short days for other crops.

Conversely, long days can be provided when the day length is naturally short by using night break lighting with incandescent or high pressure sodium lamps. This is the same technique used in lighting chrysanthemum crops to keep them vegetative until flowering is desired. Night break lighting generally occurs from 10:00 PM to 2:00 AM and is the most efficient method of providing long days. Growers may also choose to light crops for several hours at the end of each day from 5:00 to 10:00 PM.

Reprinted from "Light and flowering of bedding plants" by Beth Fausey, OSU Extension ABE Center in the February 17, 2006 edition of the Michigan State University Greenhouse Alert newsletter.

Greenhouse - Pictures of Some Greenhouse Businesses in Kent County

Some pictures of greenhouse businesses in Kent County.

Photos by Jean Thomas, Extension Program Assistant,UD, Kent County

Friday, December 26, 2008

Greenhouse - Response to Light Levels

Light levels can have dramatic affects on certain bedding plants. The following is an article on the subject from the Michigan State Greenhouse Alert newsletter.

Flowering of bedding plants can be influenced by greenhouse light conditions, specifically irradiance. Irradiance is the amount of light reaching a plant at any given moment in time. It is an instantaneous value and is measured in units called micromoles over a square meter of greenhouse space (µmol·m-2·s-1). Growers can use a number of hand-held light meters to measure irradiance in the greenhouse. Depending on the meter used, measurements may be available in footcandles or µmol·m-2·s-1. One µmol·m-2·s-1 of sunlight approximately equals 5 footcandles of light.

Bedding plants may have a facultative irradiance response where high light levels promote faster flowering or an irradiance indifferent response where high light levels do not affect flowering. Species exhibiting a facultative irradiance response flower faster because the juvenile stage of development is shortened under high light levels. As a result, plants form fewer leaves before initiating flowers than those grown under lower light levels. For example, Salvia farinacea has a facultative irradiance response. Plants generally form 24 leaves before flowering under long days yet form only 18 leaves before flowering when grown with an additional 150 µmol·m-2·s-1 (approximately 750 footcandles) of light.

It is important to note that temperature influences the rate of development, and plant temperature of species in both response groups can increase under high light levels. Plants exposed to direct sunlight can be 5 to 7ºF warmer than the surrounding air temperature. Although elevated plant temperature due to high light conditions does contribute to faster flowering, it does not influence the number of leaves formed below the flower.

Facultative irradiance plants

Flowering tobacco

Irradiance indifferent plants


Reprinted from "Light and flowering of bedding plants" by Beth Fausey, OSU Extension ABE Center in the February 17, 2006 edition of the Michigan State University Greenhouse Alert newsletter.

Landscape - Horticultural Ecosystems X

This is the last of the series on horticultural ecosystems in sustainable landscaping. Slides are from a presentation that I give on the subject.

Pest problems in the landscape result from a horticultural ecosystem that is out of balance. This often is due to lack of diversity in a landscape that leads to pest buildup. Use of plants that have noted pest problems should be reduced. Practice those methods that encourage the buildup of competitors or natural controls of pests. If pest control is necessary, practice integrated pest management and consider all options before using a pesticide.

Encouraging beneficial or benign organisms in the landscape can go a long way to reduce or eliminate pest problems. Strive for a balanced ecosystem. Understand those practices that can encourage these "good" organisms above ground and below ground.

It is critical to use native plant species as much as possible. These are well adapted plants that are important for wildlife and will help to develop a horticultural ecosystem that will function well in our area.

In the end, consider whether you want to fight natural forces or learn to take advantage of them. Highly managed horticultural systems with limited diversity and high maintenance species are costly and often do not succeed in the long term. Think of how your short term actions will end up in long term consequences. In landscape design make sure your vision includes the creation of a successful and healthy horticultural ecosystem. Strive to understand the interactions that occur in the landscape to help you make better decisions.

I hope this series has been helpful with those of you interested in sustainable landscaping.

Gordon Johnson, Extension Horticultural Agent, UD, Kent County

Thursday, December 25, 2008

Happy Holidays!

Photo by Ransom, UK

Some Seasonal Poems

"At Christmas I no more desire a rose than wish a snow in May’s new-fangled mirth;
But like of each thing that in season grows."

William Shakespeare

"I heard a bird sing
In the dark of December
A magical thing
And sweet to remember.
'We are nearer to Spring
Than we were in September,'
I heard a bird sing
In the dark of December."

Oliver Herford, I Heard a Bird Sing

Tuesday, December 23, 2008

Landscape - Horticultural Ecosystems IX

This is a continuation of the series taken from a presentation that I give on sustainable landscapes as horticultural ecosystems.

In a balanced horticultural ecosystem, plants will for the most part be healthy. However, undue stress from abiotic (environmental) factors and biotic stressors (such as pests) can upset the balance. The goal in any horticultural ecosystem is to create and maintain a healthy environment. Landscape maintenance activities should be designed to maintain plant health.

Abiotic or environmental stress factors include drought/water stress, flooding, high temperatures, low temperatures, wind dessication, physical damage, salt injury, and nutrient deficiencies. Plant health can be negatively affected if these stress factors are excessive. However, moderate stress is normal and a healthy landscape can tolerate many stresses and actually will benefit in some ways. Understanding when you should intervene to reduce stress (such as with water during a drought) is key. Other stresses can be avoided by prudent landscape maintenance activities (no damage to landscape plants for example).

Biotic stress factors in the horticultural ecosystem include the common pests - insects, mites, slugs, weeds, diseases (fungi, bacteria, nematodes), rodents, and other animal pests. Many times our pests become an issue because of a lack of diversity in landscape, improper plant selection or use of poorly adapted plants, having excess environmental stress that predisposes plants to pests, or improper landscape maintenance activities that favor pests.

As stated before, the goal is to reduce plant stress. Use of organic amendments can go a long way to reducing water and nutrient stress. Proper pruning and thinning can reduce diseases by lowering humidity around plants. Providing proper drainage can reduce the incidence of root rots. It is important when considering methods to reduce stress not to upset the balance in the horticultural ecosystem. For example, excess nitrogen fertilizer can push plants to produce too much growth. This excess growth is often more susceptible to plant diseases.

To be continued.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Monday, December 22, 2008

Nursery - Christmas Tree Growers in Delaware

There is still time to get a last minute Christmas tree. The following is a list of Christmas Tree Growers in Delaware from the Delaware Department of Agriculture. Many of these tree farms will also sell dug trees for landscapers in the spring.

Click in tables for a larger image.

You can also print this list off at

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape - Horticultural Ecosystems VIII

This is a continuation of the series on managing landscapes as horticultural ecosystems for sustainable landscaping. Slides are from a presentation I give on the subject.

Consider what effects structural components will have on the horticultural ecosystems and design to minimize negative effects. Limit root restrictions or design with rooting in mind (structural soils under walkways for example). Consider where water runoff will go and design to manage that runoff (rain gardens for example). Consider how structural components may increase radiation load, change light conditions, or limit plant space.

Consider how the landscape will be used by people and how this will effect the horticultural ecosystem. The goal is to blend man as part of the landscape.

Your management activities in the horticultural ecosystem can have major effects. Consider how you will manage the root environment. Plant nutrients and water can be limiting factors in a landscape; however, overuse of these inputs can have negative effects. Consider how your management affects light conditions, temperature, wind, humidity, and other microclimate effects.

Consider what the effects of the above management decisions would be on the horticultural ecosystem.

To be continued...

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Sunday, December 21, 2008

Visit Delaware Garden Centers and Farm Christmas Shops - There is Still Time Before Christmas

Take time to support our local garden centers and farm Christmas businesses this year. There is still time to buy some plants, trees, gifts, and decorations. It is critical in the economic downtime to support your neighbors who work hard as small business owners to make a living. Local buying supports the local community. The following are some pictures of some of these businesses in Kent County.

Photos by Jean Thomas, Extension Program Assistant, UD, Kent County.

Friday, December 19, 2008

Governor-Elect Markell to Speak at January Friends of Agriculture Breakfast

Delaware will have a new governor soon and policies that are put in place by the new administration will have many effects on the horticultural industry in the state. The following is the announcement for the January 9, 2009 Friends of Agriculture Breakfast to be held during Delaware Agriculture Week at the Harrington Fire Hall. This is an opportunity to get a feel for the new administration prior to taking office.

I am pleased to tell you that Governor-elect Jack Markell will be our speaker at the Friday, January 9th Friends of Agriculture Breakfast to be held at the Harrington Fire Hall in Harrington, DE. (This is the Friends of Agriculture connected to Delaware Agriculture Week).

Please reserve this date on your calendar and make your reservations for this important Friends of Agriculture as soon as possible. This is a very busy time for the Governor-elect but he views this as an important opportunity to connect with the Agricultural Community (this includes the Green Industry).

Date: Friday, January 9, 2009
Time: 7:15 a.m.
Location: Harrington Fire Hall, Harrington, DE
Cost: $20 for full breakfast and presentation
To register: contact Alice Moore at or 302-831-2504. Or go to to print a faxable form.

Hope to see you all in Harrington on Friday, January 9th.

Janice A. Seitz, Ph.D., Associate Dean for Extension and Outreach, Director of Extension, College of Agriculture and Natural Resources

Thursday, December 18, 2008

Business - Holiday Lighting

Landscapers have been adding many additional enterprises to their businesses in recent years from irrigation to parking lot sweeping. Landscape lighting has been a good addition to many landscape firms. With the holiday season in hand, one additional enterprise you might consider for the future is holiday lighting. The following are some thoughts on the subject:
  • While most families do their own holiday lighting, there is a growing number of people that would pay for someone to put up holiday lights for them. This is due to families having limited time with busy schedules, the aging baby boomer population that will pay for the service, and larger houses that are harder for a do-it-yourselfer to light well.
  • This is a natural business extension for those landscape firms that already do landscape lighting.
  • The major opportunity is at Christmas time. However, there are opportunities for Halloween too.
  • This concept can also be extended to the dark winter period to provide additional accents to the landscapes at night. Consider it landscaping with light. Consider the opportunities to add changing light features to the landscape you installed that vary throughout the late fall, winter, and early spring.
  • The opportunities for profit include providing the materials (material markup), installation charges, and design charges.
  • Please, no more giant plastic lighted Santa's

Gordon Johnson, Extension Horticulture Agent, UD, Kent County.

Landscape - Horticultural Ecosystems VII

This is a continuation of the series on viewing the landscape as a horticultural ecosystem. Slides are from a presentation that I give on the subject.

As you add plants to a landscape you will alter the horticultural ecosystem. Light conditions will change over time with trees and large shrubs. These larger plants will also modify exposures to wind and reduce heat loads. Microclimates around plants are determined by the plants selected and their growth patterns. Plants will also provide food for the microbial community and for wildlife. In the end, the horticultural ecosystem will develop specific complimentary microbial communities in the soil and canopy and certain complimentary animal components from earthworms in the soil to birds in the landscape.

Horticultural ecosystems will be impacted by changes in terrain, changes in light, soil disturbance, soil modification, exposures (wind and temperature), movement of water (drainage), microclimate effects (humidity for example), and interactions with microbes and animals.

On the slide above, take time to consider what the effect will be by the actions listed. For example, the addition of compost to a soil will modify the soil conditions greatly and will positively impact plant growth. In contrast, adding a paved driveway will raise temperatures nearby and negatively impact plant growth.

I will continue with this series in future posts.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Wednesday, December 17, 2008

Business - Great Blog to Visit on Green Industry Business and Economics: Dr. Charlie Hall

I just heard a talk by Dr. Charlie Hall from Texas A&M University. He has a wealth of information on the business and economics of the green industry. He writes a blog that definitely is worth visiting on a regular basis. The following is more information:

Dr. Charlie Hall's Blog

Making Cents of Green Industry Economics

About the Blog:

Why "Making Cents"? Because as margins get tighter and tighter in the Green Industry due to market conditions becoming increasingly competitive, a few cents per pot/plant can make a world of difference! Stay tuned to this site for up-to-the-minute information regarding economic factors affecting your business and strategic responses to enhance profitability!

Information on Dr. Hall

Dr. Charlie Hall, Ellison Chair in International Floriculture, Texas A&M University

Dr. Hall’s expertise in marketing is nationally recognized in academia and among the Green Industry clientele he serves. His major areas of specialization include strategic management, market situation & outlook, and managerial economics. He is an invited speaker at numerous regional, national, and international meetings and is particularly known for the enthusiasm, passion, and intensity he exhibits when speaking.

A sample excerpt from his blog post on "from Conspicuous to Conscious Consumption" an interview with Dan Stanek, Executive Vice President, TNS Retail Forward.

"What advice do you have for retailers who are (re)developing their marketing strategies?

The most important thing for retailers is to tie value and values together. When you can make a statement to offer lower price or great value and also that you are doing things “right” (such as making a donation with each purchase or using environmentally friendly materials), it will help justify the purchase for shoppers. You need to provide a reason for consumers to prioritize your purchase in their life above other things they need to spend money on."

You can view Dr. Charlie Hall's blog at

Business - Green Industry Risk Management (Business Management) Guide

When you hear the term risk management, most business persons think about insurance. However, the term risk management has been broadened over the years from an educational perspective to encompass most of the areas we used to call just plain business management. It includes aspects of production, marketing, financial management, human resources management (labor, management), legal issues, and environmental concerns along with traditional risk management with insurance. There is a great guide on business/risk management for the green industry aimed at greenhouse and nursery businesses but with sections that could easily apply to other green industry professionals. It is available for download from the National Crop Insurance Services. The following is more information.

Green Industry Risk Management Guide


Size and Structure of the Green Industry

2 U.S. Green Industry’s Economic Contributions
7 Mega Trends in the Green Industry

Overview of Risk Management Principles

10 Risk Overview
14 Risk Attitudes of Nursery Growers and Allied Professionals
17 Risk Management for Greenhouse and Nursery Growers
20 Record-Keeping: Essential to Risk Management
22 Business Planning for Nursery Managers: Charting a Course Toward Profitability

Production Risks and Responses

28 Production Risk
31 The Pros and Cons of Diversifying the Nursery Business
34 Pot-in-Pot Nursery Production: In-Ground and Above-Ground Systems

Risk Management Through Crop Insurance

36 Why Should I Buy Crop Insurance?
38 Nursery Insurance
41 Adjusted Gross Revenue Lite Insurance (AGR-Lite)
44 Selecting the Right Crop Insurance Agent

Marketing Risks and Responses

46 Marketing Risk
49 New Conditions of Sale Add to Nursery Growers’ Risk Profile
51 Eco-Friendly Diversification Strategies
54 The Basics of Pricing for Nursery and Greenhouse Firms
58 So What is the Best Retail Price?
61 Retaining Customers for Greater Sales and Profits

Financial Risks and Responses

63 Financial Risk
66 Analyzing Financial Statements for Better Management in Horticultural Businesses
69 Benchmarking Your Way to Success!
71 Handling Risk with Enterprise Budgets for Ornamental Plants

Human Resource Risks and Responses

74 Human Resource Risk
77 Labor Risk Management: How to Find and Retain Farm Labor?
78 Complying with Equal Employment Legislation
82 Selecting and Managing Agricultural Labor

Legal and Environmental Risks and Responses

85 Legal Risk
87 Legal Issues for Greenhouse Growers
90 Managing Legal Risks in Agriculture Production: Immigration and Migrant Labor Issues
93 Optimizing Pesticide Performance in Nursery Production

Authors include noted University experts who work with the green industry.

This guide can be downloaded at:

The guide can also be downloaded at:
Be forewarned that it takes a long time to download, even with high speed Internet access.

Tuesday, December 16, 2008

Some Holiday Horticultural Pictures from Kent County

The following are some holiday photos from horticultural businesses in Kent County, DE.

There are many Christmas tree farms to choose a tree from in Kent County.

We have a number of greenhouses that grow their own poinsettias in the county.

Photos by Jean Thomas, Program Assistant, Unviversity of Delaware Cooperative Extension, Kent County

Ornamental Short Courses - You Will be Receiving a Mailing Soon

Watch in the mail for information on our Ornamentals Short Course Series in 2009.

Holiday Greetings from Delaware Cooperative Extension!

The 2009 Delaware Cooperative Extension Ornamentals Short Course schedule will be mailed to you in the coming week. This year, our workshops begin in January and continue into the summer with two evening plant walks. We are offering workshops in each county that address a variety of horticultural subjects, and offer nutrient management and pesticide credits to help you maintain your certifications. This year’s schedule includes a shrub and evergreen series, an introductory greenhouse series, workshops to address sustainable landscaping, business survival, nutrient management for turf, integrated pest management, fertilizers and organic nutrient sources and more. Each workshop is reasonably priced to accommodate your needs and is offered throughout the week at various times of the day, depending on the course and also the season in which it is offered. Additionally, some workshops offer a light dinner. Registration will be accepted through the county offices; simply call your county office and add your name to the class list, and then pay at the door.

We continue to work with the Delaware Nursery and Landscape Association (DNLA) to offer annual expos and conferences to address important and timely subjects. The next conference is: Delaware Horticulture Industry Expo and Pesticide Conference, January 14 &15, Modern Maturity Center in Dover, Delaware

Delaware Cooperative Extension has many services to offer you throughout the year in New Castle, Kent and Sussex counties. You can drop off plant specimens, request assistance in identifying plants and their problems, pick up soil tests, informational pieces such as plant, insect, and disease fact sheets, our Plants for a Livable Delaware series, and registration forms for our Ornamentals Hotline publication (designed to fit our industry’s needs during the height of the season).

Finally, visit our website for additional up-to-date information . If you haven’t already, follow the link for Gordon Johnson’s commercial horticulture blog ( This blog provides important and timely Extension information from the University of Delaware, College of Agriculture and Natural Resources. Helpful information, photographs, resources, and a list of current events for our region can be found here.

We look forward to working with you in the future. If you need anything, please don’t hesitate to call or e-mail.


Your horticultural Extension Agents in New Castle, Kent, and Sussex Counties

Tracy Wooten, Sussex, (302) 856-7303
Gordon Johnson, Kent, (302) 730-4000
Carrie Murphy, New Castle (302) 831-2506

Click on tables for a larger image.

Monday, December 15, 2008

Greenhouse and Nursery - Fuel Cost Comparisons

Many greenhouse and nursery growers are looking into alternative energy sources. In order to compare alternative fuel sources for heating, greenhouse and nursery growers need to calculate a price per Btu. The following are formulas used to compare Btu's generated by different fuel sources. Information is from the University of Connecticut.

Click on Tables for a Larger Image

Landscape - Horticultural Ecosystems VI

This is the sixth in a series on viewing the landscape as a horticultural ecosystem as a part of a sustainable approach to landscaping. Slides are from a presentation that I give on the topic.

Once you have your landscape in place, the landscape maintenance company will manage the horticultural ecosystem. You can introduce new species and replace current plants. Interplant competition is a major factor that needs to be managed to favor one plant over another or to allow plants in close proximity to coexist. Growth modification will alter the horticultural ecosystem so pruning and thinning must be done with that in mind. Remember that the plants themselves will modify the landscape environment. You must also manage spread of plants and control invasives. Another point to consider is that natural succession is a strong force and plants from surrounding natural areas may come into a landscape without your assistance.

When you introduce or remove a species consider the effects on the horticultural ecosystem. Is the new plant compatible with the system? How will the removal of a plant alter the landscape?

Invasive species can be a challenge in some landscapes. Take time to understand why these species are invading your horticultural ecosystem and use appropriate control measures that do not harm the landscape.

I will have more on these topics in future posts.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Sunday, December 14, 2008

Landscape - Horticultural Ecosystems V

I often recommend that the landscape should be viewed as a horticultural ecosystem where the landscaper's influence is critical and the decisions they make can affect the balance. By understanding the horticultural ecosystem, landscapers can often make better decisions. The goal is to create a sustainable landscape system. This is the fifth in a series of slides on the subject from a presentation I give.

Diversity should be a major goal of any landscape. The diversity in a horticultural ecosystem is selected by you as the landscaper or landscape designer. Large expanses of lawn are not diverse systems. Neither are single species screens or windbreaks. Most of our landscapes have limited diversity with only a handful of mainly non-native species. This can lead to many problems such as increased pest problems, reduced habitat for desired wildlife such as birds, high maintenance requirements, and reduced longevity of plantings.

A common suburban landscape. Diversity is limited to a monoculture of grasses, a few shade trees, and a few foundation plants.

In horticultural ecosystems with limited plant diversity, the diversity of other organisms is also limited from soil microbes to desired wildlife. Food sources for native animals are limited thus limiting their numbers in communities that have low diversity of plants and many non-native plants. Pests are often more of a problem and reduced plant vigor often results. There is a reduction in the benefits from plant synergism. Landscapes can also be very monotonous and of low aesthetic value in these low diversity systems.

Create more horticultural ecosystem diversity by selecting a wide range of plants from many different plant families and using a majority of native plants. You can add diversity to any landscape by replacing existing plants with different species and by converting parts of lawn areas to landscaped areas. When adding plants or designing systems, consider how plants are placed and what effects they will have on each other. Design for complimentary effects. Alter soils to favor the species that you install. Eliminate those plants that have high maintenance requirements from a pest management perspective or that are pest prone.

I will continue these thoughts in additional posts.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County.