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There are many different approaches to mulch under fruit trees. Some people swear by it, and others rarely or never use it or recommend it. We tend to be in the latter camp.
Our fruit-growing study tour of the USA got us thinking slightly differently about mulch. We saw a number of different approaches to it in our travels.
What’s the purpose of mulch?
Mulch is intended to suppress plants growing under your fruit trees. These plants are often called “weeds”, and they don’t have a good reputation.
Sadly but unsurprisingly, it’s not hard to find orchards where the weeds have been completely sprayed out with herbicide. In that case, mulch isn’t needed because there are no plants left to suppress. In fact, in most orchards around the world killing all the plants under fruit trees is still considered to be best practise.
Yuk! Please don’t do that to your fruit trees. It’s an approach we moved away from in our orchard many years ago.
There are so many good reasons not to use herbicides. The chemicals are bad for your health. The weeds grow back and need spraying again, which is money straight from your pocket to the chemical companies. But worst of all – it’s really bad for the soil.
Weed sprays help to kill the natural fertility system (NFS) that trees rely on to get their nutrients. If you kill the NFS, you must rely on artificial fertilisers to feed your trees. That’s more money from your pocket to the fertiliser company.
There has also been speculation that using mulch may help to prevent fruit fly. However, the evidence hasn’t supported it, so we recommend sticking to the techniques in this blog.
What’s wrong with weeds anyway?
The common understanding is that weeds will compete with your trees for water and nutrients.
For mature trees, plants under fruit trees bring many benefits. We encourage you to stop thinking of them as weeds and start thinking of them as your precious understory plants.
However, for young trees, the competition argument is somewhat true. It’s definitely helpful to keep the weeds (especially grasses) suppressed while the tree’s roots are getting established.
We’ve always weeded around the very young trees in our on-farm fruit tree nursery, but these days are moving towards using woody mulch around the trees.
We also saw this in action at the Maine Heritage Orchard in Unity, Maine. This orchard was planted not that many years ago on the site of a disused gravel pit. Major soil building and remediation have been the order of the day.
Hardwood chips have been extensively used as mulch around the trees when they were planted. The same chips have also been used to build soil more generally, and as an ongoing weed suppression tool even as the trees mature. They’ve even been used to build paths.
The case for woodchip mulch under mature fruit trees
We saw a different approach in Michael Phillips’ orchard in New Hampshire. Michael is author of The Apple Grower: A Guide for the Organic Orchardist. We were lucky enough to be able to visit, spend some time with Michael and have a tour of his orchard. He also uses woodchips on young trees but welcomes a wide diversity of understory plants as the trees grow, using mulch in a more ad hoc way.
There is widespread agreement that if you are going to mulch, hardwood woodchips are preferable. This is because as woodchips break down, they provide the perfect environment for healthy soil fungi to thrive. Fruit trees prefer this fungally dominant soil, as we explain in our Soil Biology and the Soil Food Web short course.
Understanding the amazing world of soil microbes that are key to the Natural Fertility System will change the way you think about soil, fertiliser, and mulch forever.
So, to mulch, or not to mulch?
After everything we’ve seen, we’re still in favour of mulching while the trees are young, and then transitioning to either a natural or cultivated understory – a “living mulch”!
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