Rules to follow when using Mother Nature’s cover for the winter

The word on mulching is out.

Mulching in the fall is not a minefield-free activity. In fact, it can be a whole lot of work for a whole lot of nothing if not done right.

Taking a step back, mulching is largely about the use of organic materials such as leaves or bark to cover ground over perennials, trees and shrubs.

When done right, mulch keeps the soil moist. Organic mulch slowly adds nutrients to the soil. Inorganic mulch, such as gravel and red shale, also works but doesn’t add to the soil. All mulches save water and provide a more habitable growing environment.

In my windy Valleyridge yard, however, I applied a heavier layer of bark mulch (it should be less than 10 centimetres deep) than suggested last year with the expectations half of it would blow away. That fall application stayed put and kept a massive newly planted pine so soaking wet the roots rotted and the plant died before spring (pines are drought tolerant so they only need bark mulch if they are planted on a dry south slope).

Another downside to deep mulch is it can keep a garden’s soil frozen and plants dormant too long in the spring, which can stunt growth in our already too-short summer.

Mulches placed over landscape fabric, meanwhile, tend to slip on slopes and expose the layer underneath. Weeds blowing into the site then secure their roots into the fabric and hold on tight.

Once established, these weeds are impossible to pull out once established. Instead of fabric, use moistened cardboard or newspaper under all mulches to reduce persistent weed problems.

Another unfortunate side-effect of mulch is good bugs such as worms can get trapped and die underneath. Also, the good-guy parasitoids that kill harmful lily beetles need to fall on bare soil, not mulch, or they won’t overwinter.

It’s a small point, but all this mulch know-how means you need to be careful before adding materials to your garden because of unintended effects.

What about coffee as mulch? Gardeners everywhere wonder if the grounds from their morning cup of coffee are an effective mulch and the answer is definitely.

Grounds dumped on trees, shrubs and perennials supply a weak batch of fertilizer and add a small mulching effect over tender plants. New information says they also deter slugs. I made a second cup of coffee this morning and did the happy dance just to celebrate the upcoming end of slugs in my garden.

Donna Balzer is a garden writer and speaker. Check out her blog at or follow on twitter @NoGuffGardener.