Picture of the Week

August 9, 2021

Grassy weeds becoming obvious in dormant turf areas.​

Glenn Hardebeck, Turfgrass Research Agronomist, Purdue University

As the summer heat and drought slow the growth of our cool season grasses such as Kentucky bluegrass, other drought and heat resistant grasses begin to stand out.  Three here include crabgrass, goosegrass and tall fescue.  In most situations, control of these grasses is better left until this fall or next spring depending on the species.  Crabgrass and goosegrass are annual grasses that are primarily controlled with preemergent grass herbicides applied early spring.  Tall fescue is a perennial and therefore can not be removed from a turf stand with a preemergent herbicide.  Control of tall fescue requires multiple applications of a non-selective herbicide such as Roundup or if a reasonable number of small clumps are present, they can be removed manually.  Additional information can be found in these publications: AY-10-W, Control of Crabrass in Home Lawns and AY-11-W, Identification and Control of Perennial Grassy Weeds.

 

 

Click image to enlarge

multi[le grassy weeds

Green clumps of tall fescue (left) as well as crabgrass and goosegrass (bottom right) are very conspicuous in this dormant Kentucky bluegrass lawn.

crabgrass  crabgrass seethed

Top: Small, round, green stems with swollen joints (nodes) can be seen at the center of this spreading crabgrass plant.  Roots can form at the nodes allowing crabgrass to spread readily.

Bottom: Crabgrass seedheads are distinctive from that of goosegrass.

goosegrass  goosegrass seedhead

Top: Goosegrass stems develop a white, flattened rosette at the plant's center.

Bottom: Goosegrass seedheads have two flattened rows of seeds on individual spiklets.

tall fescue  tall fescue close up

Top: Tall fescue is wider bladed and more drought resistant than Kentucky bluegrass or perennial ryegrass forming clumps in a mixed stand.

Bottom: Tall fescue is not likely to have a seedhead at this time of year and is often red to purple at the base of the stem.

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