This species, an annual introduced from Eurasia, is by far the most common crabgrass at Fontenelle Forest and Neale Woods. It may be upright or spreading and often roots at the lower nodes. The flat, 1-5 inch long leaf blades have no midrib and are hairless or have just a few long hairs near the base. Leaf sheaths are flattened (keel shaped) and hairless (F). Flower stems have 2-8 flattened branches all arising from one point (digitate) or along the stem within a short distance of each other (A). Branches bear two rows of spikelets on short stalks. The close-up photo of the spikelets from the front (G, left) and the back (G, right) demonstrates their arrangement along the flattened branches. The tiny flowers consist of pale yellow anthers and purplish stigmas (I).
Another significantly less common crabgrass species, Southern Crabgrass (Digitaria ciliaris), also occurs at Fontenelle Forest and Neale Woods. The best identifying marker is the leaf sheath of Southern Crabgrass,which is covered with long, soft, white hairs. Yet another species, Hairy Crabgrass (Digitaria sanguinalis), has not been identified by the author, but has been previously seen at FF/NW and is likely present. It has more hair on the leaves than Southern Crabgrass, but other characteristics overlap and these two species cannot be reliably separated without a microscope.
Goosegrass (Eleusine indica) has spreading, whorled branches much like Smooth Crabgrass. It grows as a single firmly rooted bunch unlike Smooth Craggrass which usually spreads and roots at the nodes. Also the branches of Smooth Crabgrass are much thinner (H, left side) and the spikelets with their single floret much smaller than the Goosegrass spikelets (H, right) which have 2-9 florets.
Smooth Crabgrass is a tough plant and a serious weed in many area lawns.
The content of NatureSearch is provided by dedicated volunteer Naturalists of Fontenelle Forest who strive to provide the most accurate information available. Contributors of the images retain their copyrights. The point of contact for this page is: Neal Ratzlaff.