Suppressing weeds with a layer of mulch is without a doubt one of the best organic weed control tips out there. But, mulching only works if you do it right.
1. Apply mulch early in the season, before annual weed seeds germinate. If you wait too long, weed seeds with already have germinated and they will grow right up through the layer of mulch.
Don’t mulch until you get rid of all existing weeds first. This means taking the time to pull or otherwise remove any and all weeds, not simply dumping the mulch on top of them.
A layer of mulch doesn’t usually smother existing weeds; they’ll just grow up through it as the season progresses.
2. Only use mulches that are weed free and come from a reliable source, otherwise you could end up introducing more weeds to your garden.
We use commercially produced leaf compost in our vegetable garden and perennial beds, and shredded hardwood bark in my shrub beds.
3. Use straw, not hay, for a mulch. Straw is the dried stems of wheat or other grains and is typically weed free, but hay is mixed forage and often contains many weed seeds.
We love to use straw to mulch the paths of our vegetable garden.
4. Never use treated lawn clippings. While collected grass clippings make a great mulch in the vegetable garden, do not use them if the turf was treated with herbicides or chemical fertilizer products.
5. Don’t over-mulch: No matter what type of mulch you use, two to three inches of it is enough. If you pile too much on, you risk inhibiting air exchange with the soil and the roots of your plants.