6 tricks for using mulch in your garden

Mulch benefits the garden in so many ways that most of your plants will need some type of mulch.

6 tricks for using mulch in your garden

What mulch does

As organic mulches break down, they enrich the soil with humus.

  • Mulch insulates the soil from temperature extremes, keeping it warmer in winter and cooler in summer, and minimizes erosion, moisture loss and weed growth.
  • Earthworms are often happiest living beneath a thick blanket of mulch.
  • Organic mulches allow water, air and fertilizer to pass through, and they decompose to add nutrients to the soil; inorganic mulches are generally impermeable and durable.
  • In winter, mulched plants won't be heaved out of the ground by alternate freezing and thawing, and they won't be tempted to emerge prematurely during a brief winter warmup.

1. What mulch to use

  • Many materials make suitable mulch, as long as they cover the soil well and are healthy—that is, have never been exposed to toxic chemicals, insect pests or diseases.
  • While you can purchase mulch in bags, bulk or rolls, don't forget about materials you may have on hand, such as chipped brush, pine needles, leaves or newspaper.

2. When to mulch

  • For perennials, trees and shrubs, you can leave mulch in place year-round.
  • For vegetables and annuals, wait until the soil warms.
  • For hardy perennials that are overwintering in the ground, wait until the soil freezes to apply a new blanket of insulating mulch. Rake it back first thing in spring to help the soil warm up a little faster.

3. Two mulching don’ts

  • Don't pile mulch too close to trunks or stems. It can smother plants, promote rot and let slugs, mice and other pests hide near a food source.
  • Don't use plastic mulch around shrubs and other hardy plants. Because it's not permeable, it cuts off air and water to roots and can cause soil to heat up excessively in summer.

4. How much is enough?

  • Mulch that covers the soil to a depth of five to eight centimetres is usually sufficient during the summer months.
  • If you find erosion or weeds are a persistent problem, or if you're overwintering tender plants, spread mulch 10 to 15 centimetres deep.
  • For permanently mulched shrubs or beds, just refresh the top each year to maintain the proper depth.

5. Match your mulch to the plants

  • Acid lovers, including rhododendrons and camellias, appreciate acidic mulch. Try pine needles, oak-leaf mold, shredded oak leaves or composted sawdust from cypress or oak.
  • On plants that don't need acid, use neutral materials, such as straw, buckwheat hulls or corncobs; if you're using acidic mulch, add a little lime.

6. Don't let weeds breathe

  • Smother weeds or other undesirable plant growth with a newspaper mat.
  • Wet several sheets of paper to help them cling together, then place the mat so that plants are completely covered and no light can reach them; anchor the edges with rocks or soil.
  • Top with wood chips or other mulch as camouflage and remove it once the weeds are dead.
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