The climate emergency will be with us long after Covid 19. Trees lock up carbon so planting one in the garden strikes a blow in the climate emergency. Whatever our size of garden, we can all join the fight, whether we’ve space for a majestic oak or a dwarf Deutzia. It’s all about permanent planting.

A tree sequesters carbon for many years and its large root system plays an important role. Although all perennial planting in undisturbed ground contributes, mature trees are key players.

Your selected tree is for life and a deciduous hardwood is often much better than a conifer might be. Much as I support the Scottish Government’s tree planting programme, it is a short-term policy.

Sitka spruce plantations are felled after 30-40 years and extraction devastates the soil, releasing large amounts of carbon. Living in the Borders, I’m surrounded by mutilated, Mordor-like hills. An RSPB report showed that in 2018, carbon from 53% of the harvested timber was released within 15 years, and 23% was burned.

You largely undo your good work by felling or severely pruning a tree. So choose wisely. Ensure your preferred tree’s final height and spread will fit the space available. How will it be an asset to the garden? Will it help biodiversity, add colour, blossom, berries or act as a good windbreak? A reputable, possibly specialist nursery or garden centre with experts should advise and established organisations like Glendoick Gardens have an excellent selection and answers to all your questions.

Willows come in every shape and size, from 5m tall and vigorous to dwarf creeping ones like Salix hastata or S. helvetica that only reach 50cm. Even their little trunks store carbon efficiently.

With around 450 species, there’s a Berberis for any space. One of my favourites, Berberis vulgaris reaches 4m, but Berberis calliantha only grows to 75cm and Berberis x frikartii ‘Amstelveen’ reaches a modest metre. Most Berberis grow to around 1.5 to 2m.

Many shrubs also work. The ‘Yak’ Rhododendron hybrids reach 2.5m, with deciduous Azaleas a little less

Spread is equally important. Although Chaenomeles are usually 2m tall, their spread could be twice that. Like Loniceras, they’re probably best trained against a wall.

Even if you don’t fell an overly large tree, frequent pruning also releases carbon. So your tree or shrub should need minimal trimming. So don’t choose Cornus varieties grown for their wonderfully coloured stems or delightful Salix varieties with yellow, red and purple ones. That need to be cut back every year as the spectacular colours only appear on fresh growth.

I’m always promoting trained fruit trees but, if excessively pruned, they contribute little to the climate fight. And with apple trees height and spread are determined by the rootstock, so choose a rootstock to let your tree fit your space.

You and the new tree will be sharing the garden for a very long time, so it must appeal to more than your social conscience. Despite their bad press, there’s more to Cotoneasters than the C. horizontalis, that deadly denizen of roundabouts and supermarket car parks. Many of the 400+ species are small-medium sized, may be evergreens, have flowers with bee-appeal, and a wide selection of coloured berries.

Holly Ilex aquifolium makes the perfect windbreak. Although every form could become a proper tree, some fully grown Ilex crenata cultivars like ‘Golden Gem’ or ‘Convexa’ only reach 1 or 2 m - ideal for a smaller space.

Largely undisturbed trees of any size are a perfect haven for wildlife. They provide vital habitats for countless organisms like lichens and fungi, as well as nectar for insects, berries for birds, and shelter for hedgehogs and other wee mammals.

So get planning and planting.

Plant of the week

Prunus incisa ‘Kojo-no-mai’ The blossom opens from pale pink buds. The flowers are large and blush white. The tree slowly grows to 2.5m with zigzag branchlets and very hairy leaves.