The Age of the Big Tree
We have to rethink what we plant as the UK gets warmer and drier
By Andrew Fleming
July 5 2023
My late-17th-century house could not be more English, but its surrounding trees are anything but native. They include some magnificent Cedars of Lebanon, Turkish and Hungarian oaks, and a Cork oak planted in the 1770s by the local bishop, whose predecessors built the house itself.
I like to think the cleric had divine guidance, as these are exactly the type of trees we should plant in the UK today, for our climate will increasingly resemble that of the Mediterranean and Middle East over the next 100 years. The reality, though, is more down to earth as the bishop and his wife travelled on a pilgrimage to the Holy Land, via the Balkans, and collected seed and acorns as they went.
We have all grown up with the beauty of our indigenous oaks, beech, ash and earlier elms of hedgerows and copses spread across Britain. But unless we act now, future generations will inherit nothing but a landscape of stressed and dying trees.
Sensible projections indicate that the UK climate will be just too hot and too dry for common beech (Fagus sylvatica) and some experts say they would not plant one today anywhere south of the Wash, while ash (Fraxinus excelsior) are dying in huge numbers. Our ancient and beloved oaks (Quercus robur) are also under attack, and not just from climate change. These iconic monuments of Nature are suffering from, among others, sudden oak death and oak processionary moth infestation.
If future generations are to enjoy a wooded landscape we need to look to abroad – particularly to the Americas, the Middle East and Asia –for trees that will thrive in our changing climate.
In one hundred years’ time, London, and most of England, will have a climate most like that found in the Caucasus today, but the good news is that this region is rich in big, broad-leaved trees that will thrive in the UK: Zelkova carpinifolia (or Z serrata from Japan), hornbeams (Carpinus betulus), and the oriental beech (Fagus orientalis), which is an excellent substitute for the common beech.
From North America I would choose Liquidambar styraciflua, the black walnut (Juglans nigra), hickories (Carya ovata) and Catalpa bignoniodes. These have sailed through this summer’s drought in our garden.
Asia is rich in covetable trees, but the wingnuts (Pterocarya), Chinese mahogany (Toona sinensis), and Catalpa ovata are worth the most serious consideration for the UK’s future gardens.
I particularly want to emphasis two genera: oaks and limes. The former offers great diversity, with nearly 500 species, including recent discoveries from Mexico, while the latter seems to be remarkably disease-free and deserves to be much more widely planted. If you are interested in autumn colour as well as hardiness, the North American ‘red’ oaks are excellent. I recommend Quercus palustris and rubra.
The European oaks of the Balkans and Caucasus – Quercus frainetto and cerris – will both become great landscape trees. My particular favourite, though, is Quercus castanefolia and ours, planted 20 years ago, is already a fast-growing, handsome thing.
Of the limes, Tillia tomentosa, also from the Balkans, is vigorous, attractively leafed, and hardy certainly up to the Highland line. Others of particular note are Tillia oliveri and T. mongolica. The ‘native’ small- leaved lime, Tillia cordata, is also still worth planting.
If you only plant one or two trees, I recommend the Indian chestnut and the gingko. Aesculus indica from the north-west Himalayas is a worthy substitute for the horse chestnuts that are suffering terribly from leaf miner and canker. It is happy in most soils, including chalk; has tinted emerging foliage and flowers in June/July. Ginko biloba originates from China/Japan and was introduced to the UK in the 1730s, its long-lived survivors having been around since before the dinosaurs. They are happy in urban as well as country locations.
Future growing conditions are, in fact, highly uncertain, with a risk, for example, that the Gulf Stream will significantly weaken. If this is the case, our climate will more closely resemble Sweden or Japan, with hot summers but potentially much colder winters. Diversity is therefore the key. Think also about the origin of what you are planting and try to buy UK-grown plants wherever possible.
Finally, we need to think of future generations and not of ourselves. We planted a cedar grown from seed from the bishop’s original planting for the Queen’s Platinum Jubilee. We trust it will still be thriving in 250 years.