Mulch for Natural Weed Control

Weed problems? Want an easy, naturally organic solution? Bury the weed seeds. If they can't see the light of day, they won't germinate. Well, actually there's more to the story.

This is an easy and natural way to control weeds without the use of pesticides.

How seeds germinateBark mulch application

Numerous factors affect seed germination

  • Usually seeds over winter and wait until the next season before germinating.
  • Some sleepers wait years or decades before germinating.
  • If a seed has dried, it needs to absorb moisture before germinating.
  • Most importantly for our purposes here, the seed must be near the surface of the soil in order to germinate.

Yes, the seed's depth in the soil affects whether or not it germinates. Most importantly for this discussion, if buried too deeply the seed won't germinate at all!

Thus for practical application, this explains why an application of mulch minimizes or even stops weed seeds from germinating.

When should I put the mulch down?

Actually, this is an extremely important question.

  • For best results apply mulch before spring germinating weeds begin to germinate. In the Portland, Oregon area this would be February or maybe March. The later you wait the more weeds have the opportunity to germinate.
  • If weeds have already germinated but are still very small, you may be able to just bury them.
  • Bigger weeds need to be removed.

Compost application

How deep should the mulch be?

Good question. It depends on the seed. Generally small seeds need less mulch to prevent germination. Larger seeds such as acorns may germinate regardless of how thick the mulch is.

Generally, an inch or two is adequate.

How often should I apply new mulch?

For optimum results apply a new layer of mulch every year.

What type of mulch should I use?

Here in the Portland metro area we generally have two choices.

  • Barkdust, which comes in various sizes, sources, may be aged, etc. Any will do except avoid the chunks only type. You need the fines in the mix to keep daylight out. Barkdust decomposes slowly so it last longer than compost. It does feed the soil although not nearly so much as compost.
  • Compost, generally from yard debris. This feeds the soil and pretty much eliminates the need for supplemental fertilizer. Perennials in particular love compost. Note: Compost does not last as long, generally only a season which effectively raises the cost in the long run.

I have mulch in my shrub beds, why do I still have weeds?

Several possibilities exist here.

  • Most likely the mulch was applied in a previous year. At least some weeds were allowed to go to seed and those seeds are on the surface of the mulch. Thus, they are not buried and are free to germinate normally.
  • The mulch may not have been applied thick enough to prevent those particular seeds from germinating.
  • The mulch could have been scuffed so as to expose the seeds.

Free estimate

Contact us for a free estimate. We give special discounts in late winter months during the optimum time for mulch application.