How to Remove Dead Crabgrass
What's wrong with crabgrass? Crabgrasses (Digitaria spp.), also known as finger grasses, are hardy and stubborn plants that can ruin the look and harm the health of a lawn. They appear as unsightly patches of rough, weedy plants on lawns. There are few ways to rid a lawn of the different types of crabgrass. However, with proper overall lawn care and some know-how, keeping a lawn free from Digitaria is easy.
Types of Crabgrass: The Basics
According to Britannica, the term "crabgrass" refers to around 220 species in the Poaceae family of plants. The types of crabgrass can be annual or perennial plants, and they can be found terrorizing lawns and also in the wild around the world. In North America, there are two main types of crabgrass that plague gardeners and their beloved lawns by sprouting out of an otherwise orderly mass of grass.
The first of these is called hairy crabgrass, or hairy finger grass (Digitaria sanguinalis), which grows between USDA zones 2 and 11. According to North Carolina State University, it can spread and colonize lawns quickly. The second culprit is smooth crabgrass (Digitaria ischaemum), which grows in the same USDA zones as its partner in crime. This spreading plant is noticeable for its rolled, blade-like leaves, which are colored a dull green but take on occasional purple hues, according to Kwantlen Polytechnic University.
What's Wrong With Crabgrass?
According to Purdue University, crabgrass is a particularly difficult plant to remove from lawns. Because the joint of their stem is close to their roots, they can survive low-blade heights when gardeners try to use their lawnmowers to remove them by force. They are also capable of surviving dryness, heat and poor-quality soil much more readily than other kinds of grass that lawn enthusiasts would rather cultivate in their yards.
Crabgrasses are opportunistic plants, and they readily germinate in bare soil, including newly seeded areas or places with thin grass. All in all, it is more ugly than it is harmful to a lawn and can act as a marker for some other problems affecting the health of a lawn. The plants themselves die during the winter. That said, considering that the seeds survive the colder months, it can take years of work to totally remove an infestation after it takes hold, so patience and dedication is a must.
How to Deal With Digitaria
The best way to combat crabgrass is by having a healthy lawn, according to the University of New Hampshire Cooperative Extension. A great place to start is by checking the soil for pH, moisture, drainage and nutrients, remembering that crabgrass tends to do well in poor soil.
Next, mow the lawn to a height of 3 inches or more to shade and cool the soil, which helps prevent weeds from germinating. Note, however, that mowing the plants when they have already grown just spreads more seeds around. Irrigation is also an important factor, particularly during the hotter months and during dry spells. To better serve desirable grasses, attempt to water deeper instead of more frequently.
Both main types of crabgrass can be controlled by using herbicides before and quickly after the seeds of the plant germinate in the spring. There are numerous types of chemical crabgrass killer, including prodiamine and pendimethalin. Another option, dithiopyr, can be used on crabgrass after it germinates but while it is still quite small. This works because the seeds germinate later than the desirable competitors of crabgrass, though herbicides should always be considered a last option.
- A single crabgrass plant features multiple leaf blades all originating from a central whorl. The leaves are somewhat flat and the seeds form in rows along feathery branch tips, with up to 150,000 seeds from a single plant. The three common crabgrass species to affect lawns include hairy crabgrass (D. sanguinalis), southern crabgrass (D. ciliaris) and smooth crabgrass (D. ischaemum).
Doug Johnson is a Canadian writer, editor and journalist.