My best friends are trees

Clive Blazey tells how prodigious tree growth is dependent on fungal mycorrhizae in the soil

Heronswood's famous Hills Fig avenue

The two greatest pleasures in my life for me have been the successful nurturing of children and the planting of trees. That the children become self-supporting happens first, usually after 20 years, but 10 years later still, witnessing the maturity of trees is immensely gratifying. 30 years after planting, our Heronswood garden has some splendid specimens which add another dimension for garden visitors.

The Hidden Life of Trees by Peter Wohlleben is a best-selling book which is an intriguing personal account of his 20 years as a forester, working with slow growing, but long-lived Beech forests in Germany.

His intimacy with trees, bereft of a language of exchange, heightens his powers of observation in a similar way to Charles Darwin's explanation of the theory of evolution.

That trees have social networks is evident, because a forest of trees behaves differently to a single tree, in the same way that individual psychology is a poor predictor of social behaviour.

Without an apparent brain or nervous system that we humans understand, trees manage to communicate above and below ground, to advance their chances of survival. The fact that we have no comprehensive way of verifying that means of communication as yet, doesn't have any more validity than to question Darwin's theory. It can't be proven, but it is a theory that explains observable facts.

Tree stumps that remain alive for 500 years?

Peter stumbles across some strange-looking, mossy-like stones in the forest which, when investigated, reveal living tree bark with roots attached to the ground and chlorophyll coloured bark.

It is revealed that this ancient tree stump was felled 400-500 years before, when Elizabeth I was alive and defending Britain with an armada of boats built from timber felled from the same ancient Oak forests.

How could this tree live without leaves to photosynthesise? Because the underground roots of neighbouring trees were pumping sugar to the so-called dead stump to keep it alive.

Trees are interdependent, just like a colony of cold-blooded ants or a hunting pack of warm-blooded lions.

The underground extension to the meaning of the World Wide Web

Trees use scent (even without noses) to mount attacks against predatory insects. Oak trees under attack will pump tannins through their veins to deter insects, which subsequently protects all trees in the surrounding forest.

Whilst the air is a communication pathway above ground, the World Wide Web (WWW) is the fungal pathway underground.

However, the symbiotic community that works in the forest doesn't work with cultivated annual crops. Ploughing, that breaks up the soil before planting and again after for weed control, also breaks up the soil webs that transfer nutrients, as well as communication lines that most of us are yet to understand.

Explaining how fungal networks communicate and feed the forest

“Soil is by far the most alive and biologically diverse part of the terrestrial ecosystem” write the authors of Trees, Truffles and Beasts (pictured below).

“Plants obtain nutrients necessary for their growth through the below ground food web, without which the world 's forests would cease to exist.”

To explain in physical terms, forestry tests on a hectare of land in Oregon found that forest soil contained:

♦ 4.1 tonnes of fungal mycelium

♦ 5.4 tonnes of mycorrhizal rootlets (fungus roots)

♦ 40.3 tonnes of woody roots.

In similar Australian tests conducted in a 20 year old Pine plantation, it was found that although root biomass accounted for 25% of below-ground carbon root biomass, it consumed 40% of assimilated annual carbon.

How could this happen without beneficial symbiosis occurring?

A tree can be only as strong as the forest that surrounds it

You have probably noticed that trees planted too closely together defy the logic that the competition for nutrients will arrest their growth. This is clearly untrue, as any observer knows just by walking through a forest and seeing the amazing size of many trees that seem to become gigantic, even though many of them are literally growing on top of each other.

A local perspective

At Heronswood, our wise and free thinking gardener/propagator Jamie Alcock has begun establishing rainforest trees in the valley adjacent to the garden.

In an area which is not blessed with good moisture retaining soil, Jamie has been closely planting rainforest flowering trees, like the Flame Tree, Sandpaper Fig and Wild Plum, along with Gondwanaland Araucarian Pines such as Bunya and the eventually gigantic Agathis robusta.

This area has perpetually dry soil because it is within the root zone of a gigantic Monterey Cypress that is sucking up all the nutrients and moisture, but all the tightly planted trees have grown astoundingly fast. How can we explain the exceptional growth of the Flame Tree there if not for the World Wide underground Web?

A local perspective

At Heronswood, our wise and free thinking gardener/propagator Jamie Alcock has begun establishing rainforest trees in the valley adjacent to the garden.

In an area which is not blessed with good moisture retaining soil, Jamie has been closely planting rainforest flowering trees, like the Flame Tree, Sandpaper Fig and Wild Plum, along with Gondwanaland Araucarian Pines such as Bunya and the eventually gigantic Agathis robusta.

This area has perpetually dry soil because it is within the root zone of a gigantic Monterey Cypress that is sucking up all the nutrients and moisture, but all the tightly planted trees have grown astoundingly fast. How can we explain the exceptional growth of the Flame Tree there if not for the World Wide underground Web?

Some vital definitions

Mycelium — the structural part of a fungus, consisting of a mass of branching thread like filaments.

Mycorrhizae — the mutually beneficial symbiosis of specialised fungi with the feeder roots of plants. The fungus absorbs nutrients from the soil and shares them with the plant whilst the plant produces sugars by photosynthesis and shares them with the fungus. Their survival is mutually dependant.

A perspective of Heronswood House, as seen from halfway up a nearby Cedar!

Mycorrhizae is to soil and plants what a probiotic is to humans — it makes them healthier and stronger. Acting as an extension of the root system, it turbo boosts the roots' ability to absorb water and nutrients, which increases plant root development. A bigger root network improves plant growth, vigour, cropping and disease resistance, as well as reducing transplant stress.

Found naturally occurring in undisturbed soils, like in old growth forests, this soil fungus sends out filaments that boost a plant's root system, and while mycorrihizae is certainly not a new thing, its benefits are now available to gardeners. Often referred to as ‘soil inoculant’, it’s that little extra that can make a big difference when establishing plants, especially bare root fruit trees and roses.

More

Cook’s ‘Gondwana’ Pine

Clive Blazey explains why it thrives in gardens of all sizes and in all mainland capital cities

Growing the world’s most expensive pine tree

Preserving a fossil, or setting gardeners up for failure?

Mountain Range farm and Dapto community farm

Lance Carr feeds refugees — body and soul

The Bunya Pine: a tale as old as time

Marcelle Swanson shares her personal experience of growing up with a Bunya Pine

The National Arboretum of Doom

Peter Marshall, forester, truffle grower and expert on mycorrhizae gives his forthright view

Trees for small backyards

Clive Blazey explains why trees are the most important element in any garden, particularly in small spaces

Related Authors

Clive Blazey

Clive is the founder of The Diggers Club, a pioneer in the rescue of heirloom vegetable and fruit varieties and author of seven books on flower, vegetable and fruit gardening.

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Winter Garden 2017

Trees for a small garden plus truffles, roses, nuts and potatoes
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