The Climate Change Garden book on the importance of trees

In the second of three extracts from her new book, The Climate Change Garden, co-written with Sally Morgan, Country Smallholding’s gardening correspondent Kim Stoddart explains how important trees are for Britain’s more extreme weather-laden future

Looking ahead trees are going to be an important feature of the climate change garden, especially for those growing areas with a southerly aspect. They help to provide essential shade in summer, valuable shelter from the wind, as well as slowing water and reducing storm water run-off.

Whether they are edible varieties or otherwise, trees have a vital role to play when it comes to affording protection overall. I live in an exposed spot 700ft above sea level and use a range of trees and shrubs to provide protection against strong winds and flooding around my gardens and vegetable patch. Doing so also has the added benefit of attracting a wide variety of wildlife which works to help keep any pests in balance.

Unfortunately there will be an increased risk of disease and pests for our trees in the years ahead (Country Smallholding, August 2019, Book Extract) and getting them established in the first place will become ever harder. So, to help our fledging trees of the climate change future, here are some further ideas to help boost resilience.

Mycorrhizal root treatment

Plenty has been written about the benefits of applying a mycorrhizal fungal powder to roots before planting. Some gardeners swear by it and apply it to the roots of all their transplants and even use it on seeds, while others consider it a waste of time. The USDA Forest Service in the US has found inoculating seedlings prior to planting has increased and speeded growth.

The theory behind the treatment is sound: you want your tree roots to associate with mycorrhizal fungi as soon as possible. The fungi are fast growing and will soon produce a network of hyphae through the soil to take up water and nutrients and give the tree a good start. It is thought to be particularly important for bare rooted stock as some of their roots will have been damaged as they were levered out of the ground. These plants typically suffer from transplant shock in the weeks after planting as they are unable to take up water and nutrients from the soil until their roots have started to grow.

There is no doubt that the presence of these mutualistic fungi is beneficial to most plants and the soil. The fungal hyphae extend through the soil, binding the soil particles together to create a better soil structure and improved water holding capacity and thus better drought resilience. However, you don’t have to buy commercial powders. Any soil that has had plants growing in it should have fungal spores present, as will a compost rich in woody materials. And if you don’t have any compost you could collect leaf mould from under trees and hedgerows and use that as an inoculum for the new plant.

There are several mycorrhizal fungal products available commercially that contain a mix of UK-sourced mycorrhizal fungi, including powders that you sprinkle over roots or make up into a drench or gel. The idea behind these is to treat the roots of new trees before they go into the ground so that they are pre-inoculated with the right fungi.

Sugar and biochar

Another treatment that may be effective in helping your tree to establish itself is a sprinkling of sugar around the roots before you backfill the hole — yes sugar! This has been found to stimulate the growth of mycorrhizal fungi and may even fuel the growth of new roots. Yet another option is to add biochar to the planting hole. The recommended dosage is 5-10% biochar by volume in the planting hole before you backfill. Unlike organic matter, biochar doesn’t degrade so there is no loss of soil volume.

All about… The Climate Change Garden Book

Co-written with Soil Association magazine editor Sally Morgan, The Climate Change Garden book can be purchased by Country Smallholding readers at a specially discounted price of just £12 (including postage to a UK address) up until 30 September. Just quote CS12SEPT. For more information, visit www.climatechangegarden.uk