Blackwelder column: Make way for a better lawn

Published 12:00 am Friday, August 15, 2008

By Darrell Blackwelder
For the Salisbury Post
Lawns look better than last summer, but bermuda and crabgrass now dominate many cool season lawns. Unfortunately, these weeds thrive in heat and the extra rain has given them an extra boost.
Fescue doesn’t coexist with these weeds and they must be killed before reseeding in September.
These grassy weeds are entirely different plants with different methods of control. Unfortunately, homeowners often confuse the weeds, so identifying the grass is very important.
Bermuda is a warm season perennial grass that invades weak or thinned fescue lawns during hot weather when fescue becomes semi-dormant. The weed easily becomes established via seed, stolons (above ground stems) or rhizomes (underground stems). Roots form at the nodes or joints, allowing the grass to become well established over a short period of time.
Bermuda grass is often introduced in lawns by contaminated topsoil. Bermuda grass turns brown and becomes dormant after the first hard frost. The grass remains dormant until the return of warm weather in early summer. Patches of “dead” bermuda grass give fescue a spotty and unsightly appearance during the winter months.
Systemic herbicides containing glyphosate controls bermuda grass, but repeated applications may be needed to control this aggressive grass. Timing is critical since herbicides become ineffective as the soil temperature starts to drop in September.
Crabgrass is a lawn weed often confused with bermuda grass. It is a warm season annual grass which also thrives in hot weather. Crabgrass is endogenous, easily adapting to both wet and dry summer conditions of the Piedmont. It is the first grass in early summer to invade thin or weak fescue lawns.
Crabgrass grows as a clump grass, similar to fescue, but with a faint blue color to the leaf blade. A single crabgrass plant produces thousands of minute seed, remaining in the soil for years.Crabgrass is best controlled with pre-emergence herbicides in early spring or with post-emergence herbicides during the early summer. It is too late to control crabgrass with pre-emergence herbicides. Post-emergence herbicides kill young seedling crabgrass, but do poorly on well established plants.
Post-emergence herbicides such as MSMA may burn established fescue in hot, dry weather. Crabgrass dies out completely with the first killing frost. Dead plants can be raked and fescue can be seeded to fill the void. Glyphosate or herbicides containing diquat quickly kill crabgrass clumps.
Bermuda grass is a perennial, returning each season from underground stems. Conversely, crabgrass is an annual germinating from seed. Bermuda grass must be completely destroyed this month before reseeding fescue in September. Be certain that the bermuda grass is dead before reseeding. Your effort will be in vain if the grass is not completely killed.
Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. Call 704-216-897.
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