Does it matter if your fruit trees are organic?

It’s the time of year to be ordering fruit trees for planting this winter. Our on-farm nursery is called “Carr’s Organic Fruit Tree Nursery“, and like all the businesses in the co-op, it’s certified organic (the secret’s in the name!).

As far as we know, we’re the only organic fruit tree nursery in Victoria, which makes us a complete rarity. Clearly, most fruit trees that you can buy are not organic, so does it really matter if fruit trees are grown organically?

To answer that, we have to head into the soil.

The magical world of soil fungi

You’ve probably heard about the wonderful world of microbes beneath our feet. There are literally trillions of bacteria, fungi, protozoa, nematodes, worms, and many other organisms living in vast complex networks in the soil.

In organic farming, they’re often collectively called the “Soil Food Web”. It’s also called the ‘natural fertility system’ because it explains the way that plants naturally get their food from the soil. The system works perfectly because it has evolved with plants over the last 500 million years.

Within the Soil Food Web, there is a particular type of fungi that live in very close association with most plants, including fruit trees. You might have heard of them because they’re quite famous.

Of course, we’re talking about Mycorrhizal fungi.

What do Mycorrhizal fungi actually do?

Mycorrhizal fungi have a special place in the natural fertility system. There are two different types. Ectomycorrhizal
fungi form webs around the roots but don’t penetrate them. You’ll find these guys around the roots of hardwoods and conifers.

The more common type is called Endomycorrhizal fungi. These are found in 90% of all plants including vegetables (except brassicas and chenopods), grasses, softwoods, and, yes – fruit trees.

Endomycorrhizal fungi are incredible because they actually live inside the plants themselves. They burrow into the plant root and deliver moisture and nutrients. In return, the plants feed the fungi exudates, which are mainly sugars.

Mycorrhizal fungi effectively provide a 1000% increase in root surface area. This massively boosts the plant’s capacity to forage in the soil for nutrients and water.

Fungi feed the trees

The fungi scavenge for immobile minerals like phosphorus and zinc. They mine potassium, deliver nutrients like calcium and nitrogen, stimulate the plant’s immune response, and protect from nematodes. They also produce glomalin, a sticky
carbon substance that is responsible for 30% of all humus production in the soil.

Effectively, the plant tells the fungi exactly what nutrients they need and the fungi use their extensive hyphal networks to bring the nutrients back to the plant.

Soil scientist Dr. Elaine Ingham fondly calls Endomycorrhizal fungi the ‘pizza take-out boys’ of the soil food web.

But it doesn’t stop there. The massive fungal network also enables communication between plants and plants, microbes to microbes, and between plants and microbes.

It’s now known that when plants are attacked by pathogens, they release chemical signals on the Mycrorhhizal network to warn their neighbours. For example, broad beans have been shown to share news of aphid attacks on the Mycrorhhizal network.

It’s like a massive underground information super highway called the Mycorrhizal Network. Famous fungi guy Paul Stamets (who did a popular TED talk called “6 ways mushrooms can save the world”) calls it ‘Earth’s natural internet’.

What has killed off the Mycorrhizal fungi in the soil?

Unfortunately, these fungi are fragile and easily damaged. Some estimates are that 90% of Mycorrhizal fungi have disappeared from our soils.

Modern agricultural practices like tillage, insecticides, fungicides, and weed sprays can all kill Mycorrhizae.

One of the worst culprits is artificial fertilisers, which are all salts. The use of commercial nitrogen and phosphate fertilisers can lead to a vicious cycle where the plant no longer produces those all-important exudates that feed the mycorrhizal fungi or other important microbes with jobs like feeding the plant with nitrogen or phosphate.

Other culprits include fungicide treated seed, long fallows (where nothing is growing in the soil between crops), and the widespread use of glyphosate (yep, Roundup).

Genetically modified crops can also release exudates that impact Mycorrhizal fungi. Plants vary their exudates depending on what they need at any given time. If they are fed a junk food diet of artificial fertilisers they ‘forget’ how to feed themselves.

What is the solution?

Once you understand how important Mycorrhizal fungi are, and the fact that 90% of them are missing from our soils, you suddenly understand that yes, growing trees organically might be kind of important.

The best way to create healthy trees is to make sure they’re colonised with Mycorrhizal fungi right from the beginning. And that’s exactly what we try to do at Carr’s Organic Fruit Tree Nursery.

We grow green manure crops on our nursery patches, use minimum tillage, and use woodchip mulch designed to feed the soil fungi. The microbes in the soil are also fed regularly throughout the growing season.

We aim to supply trees that are already colonised with the all-important Mycorrhizal fungi when we send them home with you.

But it shouldn’t finish there.

Helping the Mycorrhizal fungi when you get your trees home

There is plenty you can do to support the Mycorrhizal fungi when you get your trees home. (This is even more important if you’re planting trees that were not grown organically from the beginning). We have plenty of resources over on the Grow Great Fruit website to help out, but here are a few suggestions to get you started:

  • Plant a cover crop before you plant your trees. A combination of oats and crimson clover has been shown to stimulate mycorrhizal fungi. Adding white and yellow clovers increases the effect even more. The main principle of cover crops is to have as much biodiversity as possible in your seed mix.
  • Use really good quality compost when you plant your trees. The best is one you make yourself. A teaspoon of good compost can contain as many as 5 billion organisms and thousands of different species.
  • Dip your tree’s roots in an innoculant you make yourself, for example worm castings mixed in water. Watch Dr. Christine Jones’ Masterclasses for a better understanding of biological innoculants.
Tree sales at Carr’s Organic Fruit Tree Nursery 11/07/2021. Photo: Brendan McCarthy 11/07/2021

Organic trees are in demand

We sell out of our organic fruit trees every year, and this year is looking like no exception.

Tree sales close on June 18, and trees will then be available to pick up from our farm open days on the last weekend of June (Saturday 24 & Sunday 25), and the first weekend of July (Saturday 1 & Sunday 2).

The range includes almonds, apricots, peaches, nectarines, plums, apples, pears, quinces, figs, multigraft trees, and fruit salad trees. Click here to see all the trees and place your order.