Weeds in my Lawn after Seeding

I've got Weeds in my Lawn after Seeding

Weeds in newly seeded soil are normal. Digging, scarifying or adding new soil wakes dormant seeds. Most will disappear with the first cut, but some will require weed killer.

This is quite normal for three reasons:

  • If you have turned over the soil during preparation, then you will have brought viable but dormant seeds to the surface
  • Any bare soil, whether from newly prepared or after scarifying is a magnet for airborne seeds
  • If you brought in additional soil this will contain weed seeds unless it has been sterilised

Definition of a Weed

A weed is a plant growing in the wrong place.

Reducing Weed Invasion into New Lawns

Try to avoid the peak flowering and seeding season for weeds. This is usually April to July which means autumn is the ideal time for seeding new lawns or over seeding existing lawns.

Getting Rid of Weeds in a New Lawn

You can split unwanted seedlings into 3 groups:

  • Tree and bush seedlings
  • Upright growing weeds
  • Low growing weeds

Tree, bush and upright growing seedlings will generally not survive the first few cuts with the mower so don’t panic as this could be the vast majority of the problem. The ones that will remain are the low growing ones such as dandelions, daisies and clovers which need to be manually removed of killed. 

Using a Weed Killer on a New Lawn

Weed killers will kill the vast majority of the more common weeds. Not all but most. The side effect of weed killers is that they will also detrimentally affect grass if used too often or at too greater strength.

Grass seedlings are young and tender plants so will suffer the side effects more readily. To ensure your efforts are safe for the new grass use the right weed killer when the grass is at least 3 months old.

Using Weed Killer before Sowing Seed

Pretty much the same thing applies. Weed killer has a residual effect so may harm seeds or seedlings if applied prior to seeding. Once again the safe advice is to leave a 3 month gap between weeding and seeding.