Two parts of my lawn, one on the street side of the sidewalk and the other on my neighbors side of my driveway, have a good deal of crabgrass, which I'm guessing would be best treated by waiting until spring to put down a pre-emergent treatment. The rest of the lawn has mostly scattered/isolated plants, which I try to keep up with by pulling by hand, but I was wondering if I'm making things worse by doing that because of the bare spot that is often left behind after I pull the crabgrass plant. Any advice?
Harford County Maryland
Yes, crabgrass control is most commonly handled with a spring pre-emergent herbicide. See our website publication on the possibilities: http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/non_HGIC_FS/TT-43e%2...
Hand pulling is fine, especially if the plant has not been allowed to get huge. In that case, yes, you end up with a very large bare patch which weeds (depending on when in the season you pull) may immediately sprout weeds or will start in fall. When you have big bare patches, you may want to temporarily cover then with a couple of handfuls of mulch, then over seed in fall. Whether big or small, overseeding in fall may be a good idea. Renting a slit-seeder is a convenient way to get good seed to soil contact when you have a fairly good lawn that need thickening. Crabgrass seeds need sun to germinate, so keeping your lawn thick and mowing high helps shade out crabgrass.
Read through this about seeding and overseeding:http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG102%20Lawn%20Estab...