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Using Bark Mulch in your garden borders, why and when.

Of all the products my company provide this is one of the most basic, most effective and organic.

The definition of "mulch" in the oxford dictionary is:

Mulch

noun a mass of leaves, bark, or compost spread around or over a plant for protection or to enrich the soil.

verb cover with or apply mulch.

Mulch as a protection against drought and cold

As the definition describes, mulch is perfect for protecting your plants roots, especially from drought, heat or cold. It provides a natural, recyclable barrier that "insulates" your plants roots from the external conditions.

All mulches will let water drain through from above but slow the movement back up through evaporation. This is even true of any irrigation you may apply to your borders.

Mulching however also has another huge benefit to your garden. A well applied mulch will restrict weed growth, always a battle for keen and amateur, time poor gardeners alike.

How does mulching reduce weed growth

The mulch acts by preventing light from reaching weed seeds so they don't germinate. In the first year of application, the mulch will also act as an "impenetrable" layer for germinating weed seeds that have had a "dose" of light, moisture and heat. This is not the case if you use fine "compost" type mulch like green waste compost or spent mushroom compost.

With these products, you must add enough depth that the emerging weed shoots will run out of steam before they emerge.

The most common mulch is Bark mulch. It is cheap to buy and also has a longer term effect (3-5 years is possible). Airborne weed seeds, that will attack garden borders anytime after the mulch is laid, find bark chippings an unsuitable place to germinate and grow. Even if they do survive the early part of life, they are very easily removed by hand from the bark chips as their roots are unable to lock everything together.

You can improve the effectiveness of bark mulch chippings with the use of a weed control membrane. These fabrics, when laid underneath bark chips, will allow you to use half the depth of mulch above. They also prevent interzonal mixing between the bark and the underlying soil. This means the bark lasts longer as it does not break down so fast.

Green waste compost and spent mushroom compost are often used as mulches though. They are especially useful in annual or vegetable borders where it easy to plant through the compost after it is laid. At the end of the flowering or cropping season, these products can be dug into the border and will have a superb soil improvement effect.

So now we come to when is the best time to apply your mulch

If you are applying mulch to an established border, then you can apply it any time through the winter when soil moisture is high and weed germination is low. You can still apply the mulch at other times in the year but care must be taken to ensure that weed growth is gauged, and any pernicious weeds are controlled before laying.

The same rules apply for the compost mulches applied onto annual or vegetable borders. It is best to add these mulches during the damp dormant months as weed seed contamination is low at this time of the year. You can then plant through the mulch with seedlings or seeds when it is appropriate. Don't apply these mulches too early in the autumn when airborne weed seeds are at their most numerous.


This article was written by Angus Cheyne, the proprietor of the popular landscape supplies company TurfAndStuff.com

© Angus Cheyne


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