Bridge Gardens’ Weed of the Month | Crabgrass
June 25, 2024
By Rick Bogusch
Once soil temperatures reach 55-60 degrees for several days, crabgrass seeds start germinating and become the troublesome weeds of lawns and gardens we all disdain. There are several species of crabgrass, all native to tropical, sub-tropical and warm temperate regions of the globe. The most common here are large or hairy crabgrass (Digitaria sanguinalis) and smooth crabgrass (D. ischaemum), both annuals.
Crabgrasses have wider leaves than most grasses and are also called finger grasses, because of their finger-like growth habit. Each plant can produce over 100,000 seeds in a season and seeds can last 30 years in soil, so it is no wonder crabgrass is one of the most frustrating weeds gardeners and homeowners combat annually.
Crabgrass will grow anywhere, but in dense shade and prefers compacted soil and hot, dry, sunny sites. Thin, weak lawns, especially if underwatered, and bare patches of lawn are perfect sites for crabgrass seeds to germinate. All they need is sunlight and a bit of moisture.
The best way to control crabgrass in lawns is to keep your lawns thick and healthy. Mowing high, setting your mower at 3 inches or more, and using a mulching mower to turns clippings into fertilizer, shades the soil beneath and discourages crabgrass seeds from germinating. Watering deeply 3-4 times per week is better than watering for a short time every day. Grass roots grow deeper, and plants grow stronger and more resilient. Fertilizers may not be necessary if you use a mulching mower. If you fertilize, use organic products and apply before grass growth slows in early fall.
Rick Bogusch
Garden Director, Bridge Gardens
rbogusch@peconiclandtrust.org