With hundreds of thousands of crabgrass seeds potentially waiting in your lawn, preventing their successful germination is essential. Crabgrass preventer products use what are known as “pre-emergent” herbicides, which target germinating seeds before new shoots can emerge from soil.
In spring, crabgrass starts germinating when soil temperatures warm to 55 degrees Fahrenheit for four to five days in a row. 1 Most garden centers carry inexpensive soil thermometers that can help you track soil temps and time your preventer properly. If you live in northern climates, nature helps, too. Yellow-blooming forsythia shrubs reach full bloom at the same soil temperatures that signal crabgrass germination.
Understanding the Crabgrass Cycle
Low-growing crabgrass seeds escape mowers.
Because crabgrass preventers only work before crabgrass seedlings emerge through the soil, timing applications right is critical to success. Preventers must be applied before crabgrass seed germinates. Crabgrass seeds can germinate from early spring until late summer when soil temperatures are right.
A single crabgrass plant can set up to 150,000 seeds in a season.
Lawn care companies may use either kind. If they’re treating an entire lawn with liquid, it will probably contain a fertilizer to give your lawn a shot of nitrogen.
As a general rule of thumb, it’s best to apply a granular when the grass is damp so the pellets stick to weeds. Let it sit on them for a day or two, and then water them in so the fertilizer (the feed part or the weed and feed) can go to work.
What You Need To Know
Broadleaf weed control used in a weed and feed will usually do a good job control dandelions, chickweed, thistle, milkweed, wild geranium and ivy to an extent.
Now is the time for the next treatment, which is a weed and feed.
There are two types of weed control: One is granular, and the other is liquid. The granular type is what you would likely get at Home Depot, Lowe’s and other stores if you’re going to do it yourself. Scott’s Turf Builder weed and feed is an example of granular.