Mulch – what is it?

Mulch is a thick layer of organic matter that is laid on top of the soil to protect it and the plants that grow in it. It is like an insulating blanket for the soil, keeping moisture levels more consistent, and protecting the soil from weather that can deplete nutrients. 

Mulch is an important element of gardening. It creates a habitat for micro-organisms and other creatures that inhabit our gardens, like worms and other insects who feast on the mulch, improving the quality of the soil by turning it into humus - that dark crumbly organic material that helps soil to be loose and friable so nutrients can easily move around.

 Think about the forest floor – it is never left with exposed soil. There are always leaves and flower petals decomposing on the ground. This is what we are replicating in the garden when we add mulch.

Why Mulch?

  • Bare soil loses nutrients and structure in adverse weather conditions
  • Helps soil to retain moisture, protecting it from sun and wind exposure
  • In Winter it adds a layer of protection during frosts, snow and heavy rain
  • In Summer it helps keep the soil moist so you do not have to water as often - this means that plants will be encouraged to put down deep roots to find water which enables the plant to be stronger and stand up more readily to wind and rain
  • Helps suppress weeds and those that do grow are easier to pull out as they spend their energy trying to find the light as they grow through the mulch, rather than putting down strong roots
  • Keeps your crops clean and reduces disease transfer – think pumpkins and strawberries that produce their fruit on the soil.

How to mulch

  • The most common mulch is pea straw, but you can also use rotted down leaves, compost, bark, coir mulch or grass clippings
  • Mulch needs to be thick to be effective – a general rule of thumb for pea straw is 10-15cm thick (except for grass clippings - only use a thin layer of these)
  • Before you put down any mulch, weed the ground first so that it is as clear as possible
  • Try not to dig the soil too much as this causes it to dry out and damages the soil structure – mulching over time will eliminate the need for digging
  • Ensure soil is damp before adding mulch. Water well first allowing it to soak down into the soil or wait until after a good downpour of rain
  • You will need to replenish the mulch over time as it reduces in thickness as the micro-organisms and other soil dwelling creatures feast on it. Usually, you would add a layer of mulch in Autumn after you have harvested and removed old plants, and in Spring before you plant your new season’s crops.

Getting children involved

Children love gardening, and putting down mulch is something they enjoy doing that is different to their usual gardening tasks. I have worked with children to put pea straw around strawberries and other plants.  I have also use coir mulch with them too. They love to put it on, especially when they can make it ‘rain’ pea straw. But they are also very careful of the plants when they are shown how to mulch carefully. Mulching helps to teach them how to care for their garden in a different way to just watering plants.

If you want to know more about the contents of this blog, or would like to find out more about Growing Kiwi Gardeners and how I can help you, then contact me at This email address is being protected from spambots. You need JavaScript enabled to view it. or phone on 021 0478 844.

If you have enjoyed this blog post, why not see my post titled Soil - The key to a healthy earth where I discuss looking after the soil in order to grow healthy plants.

 Other blog posts you might be interested in:

How do we stop tamariki from pulling out plants from the garden?

Why should we garden with young children?

Education for Sustainability through Gardening