How to Overseed in Spring and Prevent Crabgrass
Overseeding lawns in spring can be a challenge to keep out ugly crabgrass and foxtail. PREVENT, our most effective and longer lasting crabgrass pre-emergent, will also prevent good grass seed from germinating. The same conflict occurs when you are dormant seeding. Can you overseed your lawn in spring and keep out crabgrass? Yes, you can! Grass Pad recommends following these idiot proof steps when spring overseeding.
1. Mow the Lawn Short
Short mow the lawn to a height of 1½ to 2 inches, being careful not to scalp the lawn. This makes it easier for the grass seed to make contact with the soil. Bag the grass clippings or rake the lawn after mowing.
2. Rake and Remove Debris
Rake or sweep the lawn to remove heavy debris and lawn clippings. The grass seed needs to make good contact with the soil to germinate properly, so we want to remove everything that could be in the way. If you have any bare spots, rough the surface of the soil with a rake or something like a Garden Weasel.
3. Spread your Grass Seed
Spread your Grass Pad grass seed with rotary or hand cranked “whirlwind” type spreader. The seeding rates vary based on what type of seed you’re using. A good rule for overseeding is 5-8 lbs per 1,000 square feet for fescue seed, and 2-3 lbs per 1,000 square feet for bluegrass. Extra seed should be applied to any bare ground areas, about double the overseeding rate.
5. Cover Bare Spots
After seed has been applied, cover any over seeded bare spots with a light top dressing of sphagnum peat moss or PrimeraFC. This acts to hold moisture and absorbs sunlight to promote quick germination of the seed. Topsoil, black peat or straw are contaminated with weed seeds and are never recommended for seed cover.
6. Water the New Grass Seed
During extended periods of spring drought, as weather conditions permit, water seeded areas lightly so the soil surface remains moist. Give special attention to repaired bare areas. Bare areas larger than a dinner plate can dry out quickly from wind.
7. Apply Seed Safe
Mid-April (Tax Day): Apply Seed Safe, a crabgrass pre-emergent which is safe to use when over seeding. Seed Safe contains seed starter fertilizer to get that new grass growing strong.
What is Seed Safe?
Use Seed Safe when spring overseeding or dormant seeding to prevent annual grassy weeds. Seed Safe is a unique combination of seed safe mesotrione crabgrass herbicide and a high-quality slow release starter fertilizer to promote seedling establishment. Seed Safe is ideal for use in spring lawn renovation to keep out ugly summer weeds like crabgrass and foxtail.
Why should you wait till mid-April to apply Seed Safe? Annual grassy weeds, like crabgrass and foxtail, will not germinate until the soil the temperature reaches 55°. Seed Safe must be activated and in the soil at the time when weeds are starting to sprout. The herbicide is of no use if the soil is too cold for the weed seeds to begin growing. Applied too early, the herbicide (your money) is wasted. Seed Safe remains working in the soil for about four weeks, and if applied too early, the active ingredient will break down and be ineffective at the time it is needed the most. Historical data shows us, in our area, mid-April is the ideal window.
8. Mow the New Grass
Mow the entire lawn as needed to maintain a height around 3 inches. Mow with a sharp blade, at a time when the grass is not wet. Avoid making aggressive turns in newly seeded areas that have been top dressed. Mowing in straight lines across those areas will have minimal disturbance to grass seedlings. Do not let the grass get too tall between mowing. Routine mowing is beneficial for root growth on new seedlings.
See Related: Mowing Height for Cool Season Grasses
9. Apply Prevent
Mid-May (Mothers Day): Apply full strength PREVENT crabgrass pre-emergent to all areas ONLY after those areas have filled in and mature enough to have been mowed at least twice. If you haven’t mowed the new grass at least twice, wait until you have before applying Prevent.
Can I Overseed My Lawn After Applying PREVENT?
If you have already applied PREVENT this season, do not overseed in those areas. PREVENT will not allow grass seeds to establish. However, you can make spot repairs after an application of crabgrass pre-emergent, just follow this link to learn more.
See Related: Seeding and Repairing Bare Spots in Spring.
BE AWARE: PREVENT should not be used over areas where grass seed has not germinated. PREVENT will remain active in the soil 6-8 weeks preventing all grass seed & crabgrass seed from germinating.