Seed now to get a jump on crabgrass germination

Though spring is not our favorite time to seed, it’s important to seed as soon as possible to allow the cool-season grasses to germinate prior to crabgrass. Crabgrass germinations can occur at soil surface temperatures as low as 50F, but germination is slow and these plants (hopefully) may be killed by an ensuing frost. Most germination occurs at soil surface temperatures of 60F or higher. The table below lists the optimum germination temperatures for cool-season grasses and they are similar to crabgrass germination temperatures. Therefore, it’s crucial to seed cool-season grasses as soon as possible to give them every possible edge over crabgrass. Only a few herbicides can be used to control crabgrass during spring seedings. Siduron (PBI’s Tupersan) can be applied prior to or immediately after seeding and it will selective control crabgrass while allowing the cool-season grass to germinate. Multiple applications will be needed though. Golf courses can use Tenacity applied prior to seeding (residential and sports turf will have to wait until next year, see the other Turf Tip). Dithiopyr (Dimension and others) can be applied after the second mowing to control crabgrass PRE and POST. Drive can be applied 7 days prior or 28 days after seeding on most turf species to control crabgrass POST. Seem complicated? It is, and this is one of the primary reasons why we prefer to seed in late August when crabgrass is not a problem.

Optimum Temperatures for Seed Germination

*Temperatures separated by a dash indicate an alternation of temperatures. The first number is for approximately 16 hr and the second for approximately 8 hr, which would translate into cooler temperatures in the 16 hours of evening through morning followed by the 8 hours in the heat of the day. Adapted from Beards Turfgrass Science and Culture.