Best Mulch For Garden Plants – What Is Mulch?

Have you ever wondered if the layer of pulverised bark put around shrubs by many local authorities is for decorative purposes only, or are there other reasons for doing this?

Does it help the plants?

The practice of mulching – that is, covering the ground above the roots of shrubs and other plants with a layer of compost, peat, pine bark or one of several other materials, including black plastic – is done for several purposes.

The mulch acts as a blanket and helps to prevent the moisture in the soil evaporating during hot weather. This is of vital importance in many areas, where heat and lack of water can be serious garden problems.

The Importance of Mulching

Plants which are kept well mulched are better able to withstand sudden bouts of extra dry weather, such as periods of water restrictions.
Any mulch, if applied in a suitably thick (about 10 cm) and unbroken layer goes a long way towards smothering weed seedlings.

Organic mulches also eventually add nutrients to the soil and improve its structure.

Where To Mulch Do I Need To Mulch All of My Garden?

Are there certain parts that would benefit more than others?

Mulch plants that need plenty of moisture.

It is impractical to mulch all the bare soil everywhere in a garden.
The sections that will benefit most from a regular mulching are the garden’s long-term residents: the roses, fruit trees and shrubs – especially the surface-rooting types, such as azaleas and fuchsias.

In all these instances the plants remain in the same place year after year and there is usually room to workaround them.

The herbaceous border and vegetable garden would also appreciate a mulch, after you do your planting out.

Take particular care when laying mulch around young stems.

Which Is the Best-Looking Material To Use for a Mulch in the Flower Garden?

Peat, compost and pine bark are probably the most attractive mulches for a flower garden.

There are several other attractive options to keep the soil cool and moist and the weeds under control.

River stones are becoming increasingly popular as a mulch, but are sometimes more decorative than useful, as they can build up and reflect heat.

Stones are available in various sizes and look very attractive when used among plants such as cacti and succulents and other hardy, drought-resistant plants.

A 3-4 cm layer of grit, gravel, shingle, granite chippings or ornamental blue flints and crushed bricks can look good.

When it is necessary to dig the ground, these can he incorporated into the soil.

But this type of mulch is not suitable for very small plants or when growing fava beans.

Can I Grow Groundcover Plants as a Living Mulch?

Or will they take too much out of the soil?

These plants do mulch in a way, as they prevent weeds from growing and the soil from losing too much moisture. However, they mainly provide a living and extremely decorative cover to the ground, particularly in shrub borders.

Obviously, though, this sort of feature isn’t always suitable. You’d never, for instance, use it in a vegetable patch.

Don’t be too concerned that the groundcover will grow at the expense of the main shrubs.

In the early years, when all the groundcover plants are growing hard and filling up the available space between the shrubs, they are well away from their larger neighbours and not competing for food.

By the time the groundcover plants do form a complete carpet, the shrubs will have deep and extensive root systems and will be well able to look after themselves.

If anything, it’s the groundcover plants with their shallower roots that will suffer.

Which Are the Best Materials To Use for Mulching Around Plants? Different Ways To Mulch

Any material that you use as a mulch must fulfil three basic requirements:

It should have a loose texture so that air can reach the plants’ roots through it.

  • It should have a loose texture so that air can reach the plants’ roots through it.
  • It mustn’t blow away in a wind.
  • It mustn’t clog together when wet.

Despite these restrictions, the list of suitable substances is still a long one.

The cost and availability of the materials will quickly narrow your choice.

There are two mulches that are absolutely free. The first is a ‘dust mulch’ – a layer of loose soil a few centimetres deep, created simply by stirring up the surface with a hoe.

When this tilth dries out, it forms an effective barrier to water evaporation from the firmer ground below and weeds are destroyed in the process of creating it.

It does not, however, add any nutrients to the soil. It is not a true mulch, but only makes a crust on the surface that prevents oxygen from entering.

It may do more harm than good on plants that do not like their roots disturbed.

The fall of leaves in autumn provides the second mulch, if you gather up the leaves and allow them to rot down into a leaf mould.

This can then be spread around the base of shrubs and plants. Don’t leave low-growing rockery plants smothered in fallen leaves, though. That will encourage fungal diseases and slugs.

Other materials used for mulching are well-rotted, strawy, farmyard manure, rough garden compost, pine needles, well-rotted grass cuttings, peat, straw and pulverised bark.

All of these must be well rotted before being put on the ground.

The process of rotting down uses large quantities of nitrogen. So if you spread these substances unrotted, they take the nitrogen they need from the soil, denying it to nearby plants.

If you have to use the mulching material before it is completely rotted, sprinkle the soil with a high-nitrogen fertiliser to supply the missing nutrient.

Bark and peat can prove to be expensive mulches when used in large quantities. (Peat should be well soaked in water before use.)

You could compromise by mixing them with another, cheaper material.

Any of the following materials will be useful if you can get hold of them;

  • Spent mushroom compost
  • Seaweed
  • Sawdust and wood shavings

Sawdust and wood shavings need to be composted in the open for at least a year before being used, and nitrogen should be applied before using them.

Black plastic sheeting also makes a type of mulch, since it does keep in moisture and keep down weeds. In very hot, dry regions where organic mulching materials are not easily available, black plastic and layers of stones or pebbles can be used.

How Thick Should I Make My Mulch?

On a herbaceous border, around roses, shrubs and other established plants, a 5-10cm deep layer is best.

Smaller plants and young plants require a thinner layer, about 2,5 cm deep.

If you haven’t got enough mulch to go round, spread the appropriate depth around each plant.

When Is the Best Time of Year To Mulch?

The garden should be mulched regularly throughout the year.

Begin by putting down a thick layer of mulch around your plants in spring.

Then, depending on the weather, renew the mulch in summer to help keep the plants cool and to conserve soil moisture during the really hot months of the year.

In late autumn, put down another layer of mulch. This one will help protect plants from frost in the really cold areas as well as conserve soil moisture in areas with relatively dry winter months.

Should a Mulch Come in Direct Contact With Plant Stems?

On the whole, no.

Leave a 1.5 to 2 inch gap. Most young plants are liable to suffer if an organic mulch such as compost or manure is in direct contact with them.

Incompletely rotted compost could also burn the stems.

Any plant that’s grown as a grafted variety on a rootstock – most roses and fruit trees, for instance – runs an extra risk if any mulch is piled up against its stem.

The covering can induce the grafted variety to develop roots of its own from above the union with the rootstock. These roots can change the nature of the plant.

On a fruit tree, for instance, the new roots will overpower the dwarfing effect of the rootstock, and encourage the tree to grow larger.

Mulching With Leaves

A great way to use fallen leaves is to use them as a garden mulch. If you have access to a leaf mulcher, then this is the best way to get them into a suitable state to use as mulching material.

Mulching With Grass Cuttings

Like many other gardeners with a large lawn, I have a nagging problem of what to do with the constant supply of fresh lawn cuttings. Could I use them as a mulch?

Sorry, but no.

You’d do better to decompose them first in a pile by themselves.

Raw grass cuttings have several snags.

On an exposed site they tend to blow all over the place in dry weather. And in wet weather in any garden, they clump together and hinder the passage of air to the roots of the growing plants.

Plants mulched with fresh grass cuttings may suffer from a nitrogen deficiency, as the cuttings will absorb nitrogen from the soil as they decompose.

Moreover, there are seldom enough cuttings, however big your lawn, to put down an effective mulch over an entire border or shrubbery.

So the job looks permanently incomplete.

Cuttings can also be guaranteed to contain weed and grass seeds which, if the mulch is less than 5cm thick, may well give little weed-smothering effect while promoting the growth of grass.

A layer that thick, on the other hand, may prevent rain getting through.

Do not use grass from a lawn you’ve sprayed with a weedkiller.

Until at least the third mowing alter the treatment, don’t even compost the cuttings: throw them away or burn them.

Will Mulch Stop Fertilizer Reaching the Plants?

I may want to fertilise my flower border later in the year, after mulching, but I’m worried that the mulch will prevent the feed getting to the roots. Do I have to fork the mulch out of the way first?

No.

Just as water will seep through any mulch – except unbroken black plastic – any fertiliser is easily washed through, too.

One suggestion, though.

Try next year to put on your fertiliser – particularly a granular fertiliser such as 2:3:2 – before applying the mulch.

That way the nutrients have a shorter distance to travel and will get to the plants’ roots and benefit them much more quickly.

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