Marvellous Mulch

Mulch is one of those terms that you often hear mentioned in horticultural conversations, but what is it and how should you use it?

Both a noun and a verb, you are encouraged by articles and the TV to 'mulch' your garden at certain times of the year but you need to understand the principles that underpin it and how they apply to your garden, to make sure that you do not waste your time or materials.

What is Mulch?

Essentially it is a layer of material, which can be either biodegradable or non-biodegradable, that is placed on the top of soil around trees, shrubs and plants to help with the following:

  • suppressing weeds by blocking daylight from reaching weed seeds and encouraging them to germinate
  • retaining moisture in the soil reducing evaporation  
  • acting as insulation helping to keep soil warmer for longer in autumn and conversely keeping it cool in the summer for those plants like CLEMATIS that prefer their roots to be in cool soil but their shoots in the sun. 
  • protecting the surface of the soil from eroding especially during periods of wind and rain
  • adding nutrients to the soil by using a biodegradable mulch that will be broken down by micro-organisms and absorbed the soil 

Good examples of biodegradable mulch include leaf mould, homemade compost, well-rotted manure, straw and bark chippings, while non-biodegradable mulches range from stones, gravel and even offcuts of carpet that can take a long time to break down. 

Why do you Mulch at Different times of the Year?

Simply to provide the garden with what it needs at a particular time reflecting what is happening at the time within it.

As we approach late Autumn a lot of us are putting the garden to bed for the winter, a time when there is little or no active growth above the surface but below it roots are consolidating and growing ready for spring and the accompanying burst of energy.  Protection is the name of the game - applying a mulch will protect the soil from erosion, keep the soil warmer for longer to encourage root growth and importantly for your tender plants a layer of dry organic mulch topped off with a plastic cloche will protect their crowns from rotting over the winter.

In Spring, you want to promote growth and get the garden off to a flying start.  Applying a mulch will add nutrients that may have been washed out of the soil by the winter weather, prevent erosion of the soil, keep weed seeds from germinating and if you use a dark coloured mulch will help the soil to warm up quicker as it will absorb more heat from the sun. 

If your soil is particularly free draining or exposed to the elements, you will be used to adding nutrients and fertilise more often during the gardening year.  Mulching is the same, with a standard Spring application needing to be enhanced with a further one in Summer/early Autumn.  

How do I Mulch?

If you are using a biodegradable mulch, carefully apply it to a depth of 5-10cm on the soil surface between any trees, shrubs and perennials but without touching any stems as this can lead to rotting in wetter conditions, 

You can use thinner layers of non biodegradable mulches such as gravel but these are best used where you will not need to disturb them too often such as in a container.  In a flower bed, stones and gravel can 'disappear' or be absorbed over time and can be more difficult to work with if you wish to add more nutrients. 

Happy Mulching!!