Crabgrass
Garden Clippings for August 20, 2022
Hot, hot, and dry, dry. Summer of 2022 was perfect for beach bums. And perfect for Crabgrass.
Crabgrass loves hot, dry weather, and all over town the stuff is growing like gangbusters. That’s just fine in playgrounds and city parks, but for those who are fussy about their lawns, crabgrass is annoying. Its lime green colour, broad leaves and aggressive growth are the bane of turf connoisseurs.
Crabgrass does not show up in grass until mid-July. The first sprouts appear in the sunniest of yards, where water is scarce and soil is poor. City boulevards and south facing slopes are most vulnerable. The young shoots are erect, light green, with leaves that are broader than surrounding grass.
Within a few weeks, usually by early August, Crabgrass clusters begin to grow sideways rather than upwards. The aggressive growing blades begin to smother the adjacent grass, resulting in an uneven turf with blotches of uneven growth.
By the end of August, seed stems appear, growing upright on short stems. Seeds are burgundy, giving the lawn a slightly purplish cast. Each mature Crabgrass plant can produce hundreds of tiny seeds. Physically removing the seed heads by hand or by lawn mower equipped with bagger is a good idea.
The good news is that Crabgrass is an annual grass that will die with the first frost. The bad news is their seeds remain viable through winter and will be anxious to grow the following summer.
In Ontario and most Canadian provinces, there is no herbicide or magic cure for Crabgrass. Turfgrass specialists will tell you that the best way to eradicate Crabgrass is to follow good lawn growing practices which will cause your lawn to thrive and cause unwanted weeds to struggle.
Crabgrass will not grow in shade. Those who leave their lawn mower at its highest setting will have success in reducing Crabgrass because the taller grass keeps the soil cool. Conversely, if you scalp the grass and cut it short, you are inviting weed seeds to have a heyday.
Fertilize generously and only water when soil is consistently dry. Crabgrass will not sprout if grass is healthy and dense.
Corn gluten, a natural and safe granular herbicide, will give good control if applied in spring before seeds sprout. The best time to apply corn gluten is June when seeds are waiting for warm weather to arrive.
Keep in mind that corn gluten is a pre-emergent herbicide that will do nothing if applied to eradicate mature Crabgrass. Corn gluten will also prevent dandelions and other seeds from sprouting. Once applied, corn gluten is effective for approximately 6 weeks, so it is important not to sow new grass seed during that time frame.
Pulling out Crabgrass by hand is a daunting task but is a good option for those who have time and patience. Crabgrass is shallow rooted and easy to pull out, particularly if the soil is moist after a rainfall. The resulting holes should be quickly repaired by top dressing with a thin layer of soil and a good quality lawn seed mix.
No doubt the best way to keep Crabgrass away is to plant shade trees. The earth will thank you for doing so.
