Crabgrass is part of what we call weeds like quack grass. This weed that gardeners hardly appreciate has the nasty fault of being insistent, that is to say, once established, it never stops taking hold, although it is annual. This grass is found today in the four corners of the planet, preferably in regions with a temperate climate.
How to recognize crabgrass?
Crabgrass is a small annual grass that has several species belonging to the Poaceae family. The two most common species of crabgrass, the most annoying for gardeners, look very similar, they are:
- astringent crabgras ( Digitaria ischaemum ), also called ischemic crabgrass or filiform crabgras,
- crabgras ( Digitaria Sanguinalis ), which is distinguished by its stems with reddish reflections and its strong hairiness.
Crabgrass measures 10 to 60 cm high, and its stems are spreading then straightened, with lower nodes forming folds from which roots often extend. The pubescent leaves are quite short, 5 to 10mm wide, flat, and quite light green.
The flowers are small, thin, elongated purplish spikelets arranged like the fingers of a hand, that is to say, they are grouped by 3 to 10 with, almost, the same starting point at the top of the stem. , first erected then spread out. Flowering lasts throughout the summer period, from approximately July to October.
The elliptical, glabrous, indehiscent grains contained in the spikelets detach and fall to the ground, ready to germinate as soon as the temperature is cool enough (12-18°C). This is how crabgrass becomes a headache to eliminate, especially since each plant produces thousands of seeds whose germination period extends over several years.
The roots are therefore not the most worrying for the proliferation of crabgrass since, as an annual, it dies in winter, and its roots are not traceable like those of quackgrass. If the inflorescences of the two are quite close, the root system is quite different: tracing for quackgrass, short for crabgrass.
Sandy, dry but rich soils and hot summers favor the development of crabgrass which settles in lawns, vegetable gardens, sidewalks, or asphalt driveway crevices.
How to get rid of crabgrass?
Crabgrass seeds manage to germinate in soils that offer a little bare earth, so a vegetable garden without mulch can be taken over by crabgrass, so don’t forget to lay down mulch! Furthermore, a densely sown lawn will give the seeds little chance to germinate and develop because the shoots will quickly be crushed by lawn grasses. Conversely, a lawn that is suffering, which is marked by holes, will be the prerogative of crabgrass which will find space to germinate.
So, if you want to eradicate crabgrass from a lawn, you must start by rehabilitating it: repair and re-grass the holes in the lawn in the fall, so the grass will grow one step ahead of the crabgrass seeds which will only emerge in the spring, and with a little luck the young grass will take over the crabgrass. Then, mowing high enough allows the grass to smother the germination of crabgrass seeds.
Since it is spread by seeds, be sure to always pull out the plants before they go to seed. And if you do it later, don’t put your feet in the compost because the slightest seed will go back there unless you are sure that your compost heats up enough to destroy them.
Still, in preventive action, it seems that corn gluten, rich in nitrogen and therefore an additional fertilizer, inhibits the germination of crabgrass seeds. This yellow powder must be used following a few instructions: it is sprinkled when the earth begins to warm up, around March, on damp soil which will need to be kept wet for a few more days. Be careful, you should not use it if you have just sowed grass because it will not rise either! Today, corn gluten flour which is approved in Canada is not approved in Europe, it is not sold to individuals.
Forget herbicides which do not have the expected effectiveness and which are destructive to the environment.
