To mulch or not to mulch?

Our fruit growing study tour of the USA got us thinking about mulch, as we saw a number of different approaches to it in our travels.

An apple tree mulched with woodchips at the Maine Heritage Orchard
An apple tree mulched with woodchips at the Maine Heritage Orchard

Of course it wasn’t hard to find orchards where the weeds have been completely sprayed out with herbicide, and mulch isn’t needed because there’s no plants left.

Yuk! Don’t do that!

The chemicals are bad for your health, the weeds grow back and need spraying again ($ straight from your pocket to the chemical companies), but worst of all – it’s really bad for the soil and kills the natural fertility system that trees need to get their nutrients (more $ straight from your pocket to the fertiliser company).

So what to do? Should you just let the weeds grow? Won’t they compete with the trees?

For young trees this is somewhat true – it’s definitely helpful to keep the weeds (or you could call them precious understory biodiversity plants) down while the tree’s roots are getting established, and we 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, so major soil building and remediation has been the order of the day.

Hardwood chips have been extensively used, not only to mulch the trees when they were planted, but also to build paths, build soil more generally, and as an ongoing weed suppression tool even as the trees mature.

A tree in Michael Phillips' orchard which was mulched with woodchips when planted and has since been allowed to revert to natural understory
A tree in Michael Phillips’ orchard which was mulched with woodchips when planted and has since been allowed to revert to natural understory

We saw a different approach in Michael Phillips’ orchard in New Hampshire.

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 fruit trees prefer a 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”!

Fruit tree leaves: bonus or problem?

Here’s a question we were asked recently: as the leaves fall off your fruit trees, is it OK to let the leaves rot on the ground, or are you potentially creating a disease problem?

Autumn apricot leaves on the ground
Autumn apricot leaves on the ground

Issues like this are often decided by comparing the costs (in time, money or effort) of taking action, against the benefit.

Plus, you’ve got to consider what you’d do with the leaves if you collected them, and factor this into the equation. If they can go into an active compost system, or be fed to animals, and therefore returned to the soil, this is a very different outcome to filling up your greenwaste bin, or – horror of horrors – putting them in landfill!

In this case we’re weighing up the benefit of the lovely organic matter and nutrient provided by the leaves returning to the soil, versus the potential risk of fungal disease from any spores that are on the leaves, which may create disease in the tree next season, like Blossom blight, for example.

Blossom blight on apricot flowers
Blossom blight on apricot flowers

So, how to decide?

The rule of thumb is that it’s beneficial to let the leaves rot under the trees as long as they break down quickly (within a couple of months, and certainly before next spring).

Fruit tree leaves starting to break down
Fruit tree leaves starting to break down

If you have reasonably healthy soil with an active soil food web and plenty of worms, there should be no problem and the leaves will break down quickly. The soil food web and the key role it plays in the health of your garden is explained in detail in this short course.

If you find they’re not breaking down fast enough you can help them along by mowing them with the mower or slasher, and either sprinkle a bit of compost on top, or spray them with compost tea or worm juice to help them along.

Providing frost shelter

We’ve written about frost and fruit trees before and noted the importance of providing shelter for some fruit trees in spring, which is the danger time when a heavy frost can damage flowers, tiny fruit, or even drop-bears.

Our resident drop-bear on a freezing cold morning
Our resident drop-bear on a freezing cold morning

So today we want to talk about a few different options for providing that shelter.

The first one is to build a frame over the tree. This is a great option, because you can use the same frame for bird netting, fruit fly netting, or frost cloth, depending on your need and the season.

Frost cloth is a special, fine cloth that keeps the frost from settling on the ground, protecting the trees, vegies or other crops under it. It’s not very tough and is easy to work with – and even sew with, as you can see in the photo below where an industrious Win (one of our Grow Great Fruit Home-study Program members) is sewing the cloth to fit the frame.

Win hard at work at the sewing machine
Win hard at work at the sewing machine

You can avoid the expense of frost cloth by using old sheets. A word of warning if your cover completely covers the tree to the ground – it’s best to put it on when a frost is forecast, and take it off again (or lift it up) mid-morning or when the frost has disappeared.

A bird netting enclosure can be re-purposed to provide frost protection
A bird netting enclosure can be re-purposed to provide frost protection

Another way to provide the protection your trees need is to use assets you already have in the garden. Here’s a photo illustrating how a shed and a couple of tall trees provide a wide frost shadow.

You often won’t notice these micro-climates unless you go looking for them, so next time you have a big frost, check out your garden carefully.

Look all around for the influence of buildings, sheds, fences, water tanks and other physical assets, and also notice how vegetation like trees, grass and vegie patches can determine where the frost lands, and how it flows.

Other things you can do to protect your trees from frost include putting sprinklers on your trees, using frost fans, keep your soil moist, keep the ground cover plants under your trees short and don’t mulch (because it keeps the ground too cool).

Interestingly, all the things we recommend for soil health (like increasing the amount of organic matter in your soil) can also make your plants more resistant to frost.

This is for two reasons:

  1. Plants with a high Brix level have a lower freezing point;
  2. Soil with higher organic matter levels hold more moisture, which makes them less vulnerable to freezing.

Frost is just one of the factors you need to think about when planning your home orchard (our Home Orchard Design short course has 19 different units in it, and frost only accounts for two of them!).

It can definitely make it harder to grow some fruits in a cold climate, but with understanding and planning, it doesn’t have to be a deal breaker.