Spring is a great time to overseed an existing lawn. Sunshine is abundant in those normally shady spots, and springtime rains assure an adequate supply of moisture. Spring is also the only time you can control crabgrass with a chemical or organic pre-emergent. Unfortunately, seeding and crabgrass control don’t mix. Typical pre-emergent inhibits all grass production, good or bad.
Step 1: If you can’t decide between over seeding or crabgrass control, try Tupersan/Siduron. It is the only chemical on the market today that can selectively inhibit crabgrass germination while allowing fescues and other cool-season grasses to grow. Siduron is the active ingredient found in Scott’s Step One for Seeding and Starter Fertilizer with Crabgrass Control. These products must be applied during or immediately following seed application. Left undisturbed, Tupersan/Siduron can control crabgrass for up to five weeks. Relatively new to the market, Tupersan/Siduron is a rather costly, but effective, means of chemical crabgrass prevention.
Step 2: A slightly less costly and environmentally friendly pre-emergent, available at local hardware stores and garden centers, is corn gluten. Corn gluten is a byproduct of the corn milling process and works as a pre-emergent, while providing an excellent source of nitrogen for existing plants. Corn gluten inhibits seed germination and prohibits root production on new plants for up to six weeks. Apply 10-20 pounds of corn gluten per 1,000 square feet of lawn, water lightly and allow the lawn to dry completely. Infrequent watering and bi-annual application will enhance corn gluten’s ability to ensure a chemical-free, weed-free, thick, luscious lawn.
Step 3: Crab grass seeds begin to germinate when soil temperatures rise above 50 degrees. Pre-emergent, including Tupersan/Siduron and corn gluten, should be applied before the forsythia bushes are done blooming. If lilac bushes are in full bloom, it is probably too late to use a pre-emergent for crabgrass control.
Step 4: Pre-emergent is activated through hydration. Once pre-emergent has been applied, water the lawn with a fine soft spray. After its initial wetting, excessive rainfall or continued watering will inhibit the pre-emergent’s ability to restrict weed growth.
Step 5: Pre-emergent acts as a protective barrier on top of the soil. Raking, scratching or in any way disturbing the ground in the weeks following pre-emergent application will ultimately compromise its effectiveness.