Crabgrass emergence begins slowly when soil temperatures in the upper inch of soil reaches 54 degrees for seven days and moisture is available. This soil temperature occurs many times when the dogwood begin to flower and the forsythia flowers begin to fade. Visit greencastonline.com/tools/soil-temperature to track soil temperature for your area. Waiting to apply crabgrass preventer until just before emergence will ensure control of crabgrass later into the season. Crabgrass preventer must be applied before plants emerge, otherwise it will not be effective. After applying the crabgrass preventer, be sure to time your application just before a rainfall or irrigate the lawn to get the herbicide incorporated into the soil.
One of the best tools you can have in your garden toolbox is a soil thermometer. OSU Extension has the AM Leonard Soil Thermometers available for purchase for $10.00. All proceeds benefit the Fairfield County Master Gardener Program. If you are thinking about starting a vegetable garden the soil thermometer will come in handy to help you know what soil temperature many of your seeds need for proper germination. For example spinach will germinate when soil temperatures are anywhere from 45-75 degrees F, while green bean seed germinates more readily when soil temperatures are 65-85 degrees F.