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- One Of The Best Things You Can Do For Your Garden And Your Soil
by Yvonne Cunnington
by Yvonne Cunnington

I am a garden writer and photographer living near Hamilton, Ont. My articles have appeared in Chatelaine, Canadian Living, Canadian Gardening and Gardening Life magazines. My book for beginner gardeners, Clueless in the Garden: A Guide for the Horticulturally Helpless (Key Porter Books) was published in 2003.

My husband and I tend a large country garden, which has been featured on TV’s Gardeners Journal and in Gardening Life magazine. We have had numerous bus tours visit our garden.

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June 17, 2007

A well-mulched perennial garden

Have you ever noticed how nature quickly covers bare patches of soil with weeds? Well, that's one way of making sure soil stays in place, but gardeners aren't exactly in love with weeds. You can do your part by covering bare soil between plants with a layer of mulch. It's a job that makes other garden chores easier because, as well as making your beds look neat, mulch does a lot of other neat things:

  • It keeps weeds down, mainly by blocking out the light they need to germinate - and if a weed manages to poke through, it's easier to pull it out when rooted in a layer of mulch than in the soil.
  • Preserves soil moisture by reducing evaporation, and helps prevent erosion caused by rain and wind. Bare soil often gets a crust on it that prevents rain from penetrating easily.
  • Keeps soil temperatures cool in summer and helps to reduce the risk of damage to plant roots in winter.
  • Helps keep soil from splashing onto leaves, which keeps plants looking neater and helps prevent soil-borne fungal diseases.
  • As mulch decomposes, it adds all-important organic matter to the soil and keeps the top layer of soil loose and airy.

It's hard to think of another garden job that provides so much payback. The how-to is simple: just layer the stuff two inches to four inches deep over bare soil near your plants. Just don't put it right on top of plants, and keep it from touching the bark of trees and shrubs since excess moisture there can promote disease and rot. Add mulch to your garden in spring before hot weather comes and while annual and perennial plants are still small enough to work around easily. (As for what to use, see below.)

Some gardeners add winter mulch to give extra protection to plants - this doesn't keep plants warm, but keeps soil temperatures even, a good idea in areas where winter brings alternating periods of freezing and thawing and where there isn't enough snow cover to give plants a thick insulating blanket. Boughs cut from your Christmas tree make good winter mulch, and have the added bonus of trapping snow that might otherwise blow away.

Mulch: Best bets

Perhaps the strangest mulch I ever saw was a wine corks spread all over a flowerbed. It works just fine (cork is a natural material), if you don't mind your neighbors speculating on your drinking habits. Here are the more conventional mulch choices:

  • Bark or wood chips: Available shredded or in small or large chips, it's excellent under trees and shrubs.
  • Cocoa bean shells: Good for flowerbeds. Will make garden smell like chocolate at first, but the scent fades quickly. It can get mouldy if you lay it on too thick - don't add more than two inches - but generally the mould doesn't cause any problems. Cocoa mulch is light and can blow away, but I find that watering well after spreading helps keep it in place.
  • Compost: Your plants will love it, but unless you have a huge compost pile or can purchase a supply, it's hard to have enough on hand for mulching. When I use compost this way, I top it with another material such as leaves or straw because compost happens to be a fertile launching pad for weed seeds.
  • Grass clippings: When fresh, they have high moisture and nitrogen content and can get smelly. The solution: apply a thin layer. Don't use for mulching when grass is going to seed, otherwise it can germinate in your beds to create a grassy weed problem.
  • Fall leaves: Nature's favorite mulch - great masses of them are free in fall. They're best used chopped - otherwise they can mat and stop air and water movement into the soil. To chop, use a leaf shredder, drive your lawn mower over them or put them in a sturdy plastic garbage container and chop with your weed eater. Use them as winter mulch or save in bags or in a pile for spring mulching of shrubs and flowerbeds.
  • Straw: Keep any bales you buy for autumn decoration because straw makes great mulch for vegetable gardens and also excellent winter mulch. With straw I used to find my biggest weed problem was grain growing from the stray kernels in the bales. But now I store the bales uncovered outdoors over winter: the bales get wet, causing the grain to germinate in autumn's warmth, then winter cold kills them off. Presto: come spring, I've got problem-free mulch. The slight spoiling isn't a problem. (Hay is full of seeds so don't use it as mulch.)
  • Pine needles: Long lasting, light and easy to come by if you have pines - each fall they drop a pile of needles. Leave in place in top of soil under your trees or rake up to use elsewhere in the garden. Cones from pines and other evergreens can also be used as mulch.

Beware of nitrogen robbers

Always layer wood chip or bark mulch mulches on top of your soil-avoid mixing them in. Mulches high in carbon-anything brown-can steal nitrogen from plants. Instead of being there for the plants, soil nitrogen gets used up by the soil microorganisms in the process of breaking the stuff down. However, layering carbon mulches 2 to 4 inches deep over the soil usually doesn't create problems and doesn't take up huge amounts of nitrogen because the mulch breaks down slowly with just the upper layer of soil being the site of all the action. You can make up the difference by giving your plants added nitrogen fertilizer.

Non organic mulch

As with many things in horticulture, there are exceptions to the mulching advice: organic mulch isn't necessarily good for all plants. Many alpines (plants from the world's mountainous regions), natives of the Mediterranean and the North American west don't like the added humus and moisture that traditional mulches deliver. Instead, try mulching them with a layer of pea gravel.

©Adapted from Clueless in the Garden (Key Porter 2003) by Yvonne Cunnington. All rights reserved.




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