byMike Supdated
Apply pre-emergent herbicide and fertilizer at the same time in spring to kickstart your lawn. Pre-emergent and fertilizer work well together because both need to be watered into the soil to be effective. By applying both at once and watering them in, you simultaneously feed your grass and stop weed seeds from sprouting. This means more of your fertilizer will feed your lawn and fewer nutrients will be stolen by weeds.
Combination pre-emergent herbicides/fertilizers are available. Purchasing one of these combination products is less expensive than buying two products. Plus, you only need to spread one product, reducing the amount of work required to launch your spring lawn.
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What is the Best Pre-Emergent Fertilizer Combo?
Scotts Turf Builder with Halts Crabgrass Preventer is an excellent product that combines pre-emergent application with lawn fertilizer and is one of the best pre-emergents for your lawn. Simply spread the granules as product label rates in spring.
- Combines pre-emergent and fertilizer in one bag.
- No mixing products required—spread Scotts Turf Builder with Halts and you’re done.
- Make the first application in early spring, when soil temperatures reach 55℉ (13℃).
- Make a second application 8–10 weeks later to feed your lawn and stop summer annuals from sprouting.
Scotts Turf Builder with Halts contains 30% Nitrogen and 4% Potassium. This provides ample growing energy for lawns, encouraging blade growth and contributing to a greener lawn in just 2–3 days after application. At the same time, the pre-emergents in the mix will serve as weed control, killing any weed seeds as they germinate below the soil’s surface.
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Should You Mow Before Pre-Emergent and Fertilizer Application?
It’s a good idea to mow grass to a height of 2–2.5 inches (5–6.5 cm) before applying pre-emergent and fertilizer. Both pre-emergent and fertilizers must penetrate the soil to be effective. By mowing your grass slightly shorter than usual, you ensure that more granules land on the soil surface, where they can easily soak into the ground once watered.
- Mow grass lower than usual (2–2.5 inches blade height) before spreading pre-emergent and fertilizer.
- Mowing low allows granules to reach the soil, where they can dissolve and penetrate to provide nutrients and weed control.
- Fertilizer/pre-emergent granules caught in grass may not reach the soil. Even when watered, the product may evaporate off grass blades.
Mowing just before fertilizer and pre-emergent application is a good rule of thumb to get the most out of your product application.
Should You Water After Applying Pre-Emergent and Fertilizer?
Water your lawn immediately after you finish spreading pre-emergent and fertilizer. A half-inch of water (about 30 minutes with a sprinkler) will provide enough water to dissolve granules and pull them into the soil.
- Water your lawn for 30 minutes after fertilizer/pre-emergent herbicide application.
- Unwatered pre-emergent and fertilizer will be ineffective.
Fertilizer and pre-emergent that haven’t been watered into the ground provide no benefit. If you wait too long after application before watering, lawn traffic may spread the product unevenly, making it less effective. Also, there’s no reason to wait. As soon as you water the product in it will start killing weed seeds and feeding your grass.
Can You Apply Pre-Emergent and Fertilizer to New Lawns?
If you have seeded your lawn in the last 12–16 weeks, or plan to seed within the next 12 weeks, do not apply pre-emergent. It will kill grass seeds and young grass sprouts. Avoid using any fertilizers that contain pre-emergents, also known as crabgrass preventers. These products will harm your grass seed.
- Do not apply pre-emergent to a lawn that was seeded in the last 3–4 months.
- Do not apply pre-emergent if you plan to seed your lawn in the next 3 months.
- “Crabgrass preventer” products are pre-emergents. They will kill grass seed as it sprouts.
- Use a lawn starter fertilizer on new lawns.
Use this lawn starter fertilizer on newly seeded lawns. You’ll have to skip the pre-emergent until the grass is mature and has been mowed 3–4 times, but a good starter fertilizer can help the grass grow thick and choke out weeds.
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How Soon After Applying Pre-Emergent Can You Fertilize?
It’s an excellent idea to apply pre-emergent and fertilizer at the same time. The two products work hand-in-hand. The fertilizer delivers nutrients to the soil and the pre-emergent kills weed seeds as they germinate. This ensures that only your lawn grass receives those fertilizer nutrients. If fertilizer is used without pre-emergent, there’s a greater chance for weeds to crop up and steal those soil nutrients for themselves.
Combination products containing pre-emergent and fertilizer are commonly available. These are great because you only have to spread one product to feed your lawn at the same time you stop grassy and broadleaf weeds. Applying pre-emergent and fertilizer at once means half as much work and is less expensive than buying both products separately.
