University of Delaware Cooperative Extension, Kent Co., Commercial Horticulture Information: Annual Bluegrass

Showing posts with label Annual Bluegrass. Show all posts

Wednesday, April 29, 2009

Landscape - Cool Season Annual Grass Weeds in Landscape Beds.

The following is a short article on two common cool season grass weeds found in landscape beds in the spring.

Cool season annual grass weeds in landscape beds.

There are two cool season annual grass weeds that are commonly found competing in landscape beds during the spring. Annual bluegrass is easily identified this time of year by its compact growth and production of many seed heads low to the ground. When annual bluegrass infests ground covers and perennial beds it can form a dense mat that will stunt plantings. Downy brome is another common winter annual grass that is highly competitive in ground covers and perennial beds during the spring. It has a more upright growth and can be identified by its densely hairy leaves and sheaths and drooping oat-like seed heads when mature. Both these species will die out by mid-June. However, they will have reseeded leaving a seed bank for germination in late summer.

Effective control of these grass weeds can be obtained with the use of preemergence herbicides applied in late summer (such as prodiamine). Non selective herbicides such as glyphosate, glufosinate, and pelargonic acid can be used as spot treatments at any time but are most effective on young plants that are not fully tillered. If escapes are found in beds, it is important to control these species in late winter or early spring before they start to produce seed heads. Selective over-the-top postemergence grass herbicides for downy brome in landscape beds include sethoxydim, fluazifop-P-butyl, and clethodim. Only clethodim is effective on annual bluegrass. Large, well tillered plants or plants with seedheads may not be adequately controlled by these materials and may still reseed.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Wednesday, August 6, 2008

Turf and Landscape - Plan Now for Winter Annual Weed Control

Winter Annual Weeds will be starting to germinate in late August and will continue through the fall. Now is the time to plan control programs. The following is information on the subject.

Winter annual broadleaf weeds of turf and landscapes include common chickweed, henbit, purple deadnettle, field violet, annual speedwells (corn, ivyleaf, purslane, and Persian speedwells), and mustard family weeds including wild mustard, wild radish, bittercress, yellow rocket, and shepard’s purse. Winter annual grasses include annual bluegrass, annual ryegrass, and downy brome. Several short lived perennials and biennials will also be germinating during this time such as mouseear chickweed and marestail (horseweed).

Preemergence herbicides can be effective in reducing late germinating winter annuals; however, many of these weeds germinate from fall through spring requiring longer residuals. Dithiopyr, pendimethalin, or prodiamine are recommended as late summer applications for the control of annual bluegrass in established turf . OH2 and Rout are examples of preemergence materials highly effect in landscapes on mustard family weeds, speedwells, Lamiums (henbit and purple deadnettle), horseweed, and annual bluegrass. They are weak however on chickweed which is better controlled with herbicides containing isoxaben (Snapshot, Gallery), pendamethalin (Pendulum, others), trifluralin (Snapshot, others), or prodiamine (Barricade). Check with each product label for compatibility with specific landscape plants and efficacy on specific winter annual weeds. Often it is more economical to allow cool season weeds to germinate and then use a post emergence herbicide. In turf, broadleaf herbicide combination products are effective on winter broadleaf weeds when applied in the fall or early spring. Non-selective herbicides (such as glyphosate) can be used for winter weed control in landscape beds with minimal cautions after leaf drop in deciduous plantings and as directed applications around evergreens.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Tuesday, July 1, 2008

Turf - Plan Now for Annual Bluegrass Control

By now, turf areas that had annual bluegrass will have died out. Note these areas and plan for late summer control measures.

Annual bluegrass, Poa annua var. annua can be a very difficult weed in turf and landscape beds. To make matters worse, a perennial form Poa annua var. reptans is also found, primarily on golf greens. Annual bluegrass tolerates low mowing and compaction. It is a prolific seeder and can quickly infest an area. Annual bluegrass starts to germinate in late summer as soil temperatures drop below 70°F and continues to germinate throughout the winter. Annual bluegrass is a problem in turf because it forms a weak sod, provides poor footing on athletic fields, produces unsightly seed heads, and dies out in late spring. In ornamental plantings it can compete with perennial landscape plants and groundcovers in the cool season.

Control starts with reducing spread by equipment. Maintain grass or groundcover vigor to shade it out, reduce compaction with aeration, increase mowing height, and avoid overwatering that encourages annual bluegrass growth. Withholding water can help to stress and kill out annual bluegrass in some cases. Preemergence herbicides such as dithiopyr, pendimethalin, or prodiamine can be used to limit seedling germination on established cool season turf. Make the application before seed germinates in late August when soil temperatures go below 70°F. Use benefin if fall seeding is planned (wait 6 weeks). Ethofumesate (Prograss) is the only selective herbicide for postemergence annual bluegrass control in cool-season turfgrass. Apply ethofumesate during the peak of annual bluegrass germination and again just before winter. Do not use on turf containing fine fescues (cannot be used on lawns with shade mixtures for example). In landscape beds, preemergence grass herbicides will give some control late August applied, non-selective herbicides can be used spot sprayed, and clethodim (Envoy plus) can be used as a selective post-emergence control. Mesotrione (Tenacity), a new herbicide registered for golf courses and sod farms, will good annual bluegrass control pre and post.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County