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when to apply weed and feed on newly seeded lawn

Before you plant grass seed, you should always prepare the area by removing any weeds that may be growing in the location. Even with careful preparation of the planting site, weeds can still develop among the newly planted grass seed. Weed killers, however, can harm grass seeds and seedlings if applied too early or improperly.

You can control weeds in newly planted grass seed and seedlings without the use of herbicides. Manually pulling the weeds by hand when they first appear keeps them from producing seeds and prevents the problematic plants from spreading, according to the University of California Statewide Integrated Pest Management Program website. They suggest keeping the newly planted grass weed free with proper mowing, irrigation and fertilization. Since newly planted turfgrass has short roots, keep the root zone moist by watering the soil lightly. However, avoid over saturating the soil. After the turfgrass has become established, promote deep and healthy root growth by watering infrequently but deeply.

Application Timing

Remember that all herbicides are different and the exact time you must wait to apply weed killers to newly planted grass will vary from one product to another. Also, some herbicides cannot be applied to certain species of turfgrass. For best results, always refer to the herbicide bottle’s label.

Weed management should be completed before seeding the lawn with a non-selective herbicide seven to 14 days before you till the soil. A second application of the herbicide may be required to kill any weeds you missed during the first treatment. Wait another seven days until tilling the soil if a second application is used.

Some pre-emergent herbicides can safely be used during seeding and usually come mixed with a seed starter. These products have the active ingredient Siduron – also known as Tupersan – that works by suppressing weed seeds while improving root development of the new grass. The fertilizer and pre-emergent herbicide mix is applied with a drop or rotary spreader using a rate of 2 1/2 pounds per 1,000 square feet. The spreader setting and actual application depends on the brand of starter fertilizer plus weed control you use, and you should always follow the instructions found on the label.

However, you can get rid of these weeds just as fast as they have appeared.
The important thing to remember when new weeds appear in your newly sown lawn is not to act hastily – do not apply a Feed, Weed and Moss Killer type product of any kind on a newly sown lawn.

If you find that the weeds are recurring past the 6-8-week mark, you may wish to consider using a selective herbicide to spot spray your weeds. Some weed killers such as glyphosate (Roundup) kill more than just weeds, so it is important to not apply these as if they are not done precisely, they can kill your grass. Shop bought selective weed killers will recommend when to apply their product and how often and you should read the instructions thoroughly and adhere to them.

In short, here’s what you should do if you encounter weeds in your newly seeded lawn:

Although this can be frustrating and we can appreciate that a quick solution will be desired, the good news about these types of weeds is that they are largely shallow rooting and should come out with the first mow at the 6-8 week mark after sowing. If they don’t, they should be easy to pull out of the turf.

If you find that when the lawn is at least six months old and has been taken over by weeds or moss, you can use a Feed, Weed and Moss Killer product.

This happens to everyone when seeding a new lawn – it’s part of the process. Wind, rain, birds, a funny bump with your spreader, or just a heavy hand with the rake when raking in your seed can all cause some sections to get a little less seed than others. Patch ’em now and in 3 more weeks you’ll have a beautiful lawn! Good luck

Hi Sarah,
I overseeded two weeks or more ago and am just now starting to see some of it grow. I didn’t fertilize immediately before or while planting. Is it too late to apply any fertilizer of any sort, starter, etc? For full disclosure of the situation, I had applied a weed and feed probably 5 to 6 weeks before planting seed, not realizing part of my lawn was only weed, which resulted in lots of brown, bare areas! That’s why I overseeded with Kentucky 31 Tall Fescue later. I’ve been watering everyday since planting.

While you may be eager to fertilize again to encourage growth, fertilizing too often is harmful. It can burn your grass, leach into the water table, and more. It’s important to wait a minimum of four to six weeks before another application of fertilizer, and I recommend 6-8 weeks.

by Sarah The Lawn Chick

Fertilizer provides grass seed or newly germinated grass with concentrated nutrients. While you could introduce fertilizer at any time (or not at all), fertilizing grass at just the right times in the growth cycle can put your grass into “hulk mode” – if you will. The nutrients available in fertilizers also come in varying percentages that can be more beneficial for different stages of growth. Choosing a fertilizer that is too highly concentrated can actually burn your lawn!

So, after preparing your soil for seed or sod, the last step before planting is to fertilize the soil with a starter fertilizer. This can be done before you lay seed or sod, or at the same time.

We have been following our local seed & garden store’s advice on a new lawn- no fertilizer till 3rd mowing., then apply starter fertilizer. So far it looks beautiful. They said to then apply a regular fertilizer after 6 more weeks. As we just read your advice and it differs should we do anything different since the starter fertilizer was applied later? What fertilizer should we switch to?

That being said, too much can lead to burning and using the wrong fertilizer can have far-reaching effects on the soil in your area.