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How and When to Mulch your Perennial Beds

Posted in Garden Advice on October 01, 2018

Garden Mulch 

Mulching improves the soil around plants, but it also gives your beds a neat, tidy appearance and will reduce the time spent on watering and weeding. Mulching helps retain soil moisture in summer, prevents weeds from growing and protects the plant roots from frost in winter.

Why to Mulch

Mulch is more than a decorative finish to your shrub borders and the perennial beds. Mulch will act as insulation to protect plant roots from drying heat and damaging frost. A 5 cm layer of mulch will protect roots from drying out in the summer sun and protect roots from the freeze-thaw cycle of winter. It will also hold in moisture around the roots on those hot summer days.

When to Mulch

Mulches are best applied in late spring and autumn when the soil is damp and warm. Avoid applying mulch in winter or early spring as the soil is too cold, and in mid-summer, when the soil will be too dry. They can be applied to new plantings and to established beds

What to Mulch With

Biodegradable mulches break down gradually to release nutrients into the soil and help improve soil structure. Layers need topped up each year or replacing when the material has fully rotted down. The best materials are garden compost, leaf mould, spent mushroom compost, wood chips, well-rotted manure, pea straw and seaweed. Note that, depending on the quality of the material, there is a possibility of introducing weeds, pests and diseases to the garden. Composts should be well rotted.

How to Mulch

Avoid mulch touching the stems of the perennials or shrubs. Never mound mulch up onto the trunk of trees. Mulch against stems or trunks may cause the bark to become diseased and rot over time, which may lead to the death of the plant.

To be effective, biodegradable mulches need to be between at least 5 cm and ideally 7.5 cm deep. Spread mulches over moist soil, after removing weeds, including their roots and when the soil is not frozen. When creating new beds, planting through the mulch layer is effective. Single trees and specimen shrubs are best mulched to the drop line (out as far as the foliage spreads).

Mulch Next Year

As the mulch ages, it will naturally turn into organic material that will improve the soil in your shrub borders and around your perennials. Once you have mulched your plants, you will find that next year, and in years to come, you will only need to add a 2 cm layer of mulch to freshen it up. You will not need to remove the mulch and replace it with a new layer.

David Brittain

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