What’s the difference between crabgrass and quackgrass?
To effectively get rid of weed grasses from the lawn it helps to understand their life cycle; this is a brief look at two common weed grasses.
Crabgrass (Digitaria sanguinalis) is the annoying broad bladed light green grass with a rougher texture than lawn and turf grasses. Crabgrass is an annual and will germinate in spring, then grow aggressively in summer and leave new seeds behind as it dies in late fall. New plants from the seeds left behind will be back next year so the best way to get rid of it is preventively. Crabgrass grows low to the ground forming clumps and can be pulled easily especially when young as the root system is shallow.
Quackgrass (Agropyron repens)is a perennial grass sometimes known as couchgrass and witchgrass. It grows from a system of underground rhizomes that spread outward from the main plant sending up new plants making it more difficult than crabgrass to get rid of. Seedlings can be pulled easily, but once mature it’s tougher.
The blades of quackgrass are long and tapered and the stems are hollow; it grows tall and upright, not branched like crabgrass. Quackgrass prefers full sun but will grow almost anywhere.
Getting rid of crabgrass and quackgrass
Corn gluten – organic weed control
Besides pulling weed grasses by hand, an early spring application of corn gluten will control them. Corn gluten is a non-toxic natural alternative to chemical weed control products and is both a plant food and a pre-emergent weed inhibitor.
The way corn gluten works is that it dries the seeds as they break open preventing roots from forming and without roots a plant can’t grow. As a plant food, the N-P-K ratio is a higher nitrogen to minimal phosphorus and potassium. Corn gluten will also prevent dandelions, fox-tail, barnyard grass, creeping bentgrass, smartweed and Bermuda grass.
Pre-emergent and post-emergent herbicides
A pre-emergent herbicide applied early in spring will control both crabgrass and quackgrass and a combination herbicide plus fertilizer will strengthen lawn and turf grass making it more competitive with the weed grasses preventing their spread. Pre-emergent herbicides prevent seed germination and therefore prevent both weed grass and turf grass seeds from germinating. Wait a couple of months or until fall to add new seed to the lawn.
Post-emergent herbicides like Finale and Roundup will kill quackgrass any time during the life cycle of the plant but they will also kill anything else green. If applied directly to troublesome weeds, the area may be reseeded again within seven days (unlike when pre-emergent herbicides are used) as they continue to affect seed germination for about 30 days.