London leaves: a snapshot of autumn 2022

This text is a part of a information to London from FT Globetrotter

Normally, the primary timber we see turning are the ash timber — particularly the American ash, which has such great deep purples and reds. The widespread ash’s leaves flip yellow on the similar time, they usually look superb collectively. Presently we have now good circumstances: heat days, cooling off at evening, which are perfect for autumn color.

This 12 months, nevertheless, due to the summer season’s unusually excessive temperatures, we’re seeing a staggered autumn. We aren’t getting the total blaze of color . Bushes are coping with the seasons individually, as all of them have completely different drought methods.

Many timber, together with horse chestnuts, walnuts and tulip timber, misplaced their leaves earlier than common in a “false autumn” and have already gone into early dormancy for winter. Because of the summer season drought, timber similar to these misplaced an excessive amount of moisture from their system, and their manner of saving vitality is to drop their leaves. English oaks, however, aren’t even beginning to enter autumn. They’re nonetheless holding on, utilizing these unseasonably heat autumn days to retailer up vitality for hibernation as a way to bud subsequent spring.

We are going to see a excessive tree-mortality price in spring, as plenty of them don’t have the sugar and saved carbohydrates wanted for subsequent 12 months’s progress. Spring is probably the most tense time of 12 months for timber, and in the event that they haven’t saved sufficient vitality they may not be capable of push out leaves. Little buds will seem, however there is not going to be sufficient energy for them to develop additional, and the tree dies.

That is the primary time in residing reminiscence I’ve seen such grave results of warmth and drought stress. The timber have tried to attract water from the soil, nevertheless it simply isn’t there. Frequent beech is my highest-risk tree within the arboretum — it doesn’t like drought. We’re at present dropping a lot of mature beeches.

At Kew, we’re starting to determine species that can be capable of take care of local weather stress sooner or later. Mediterranean timber present extra resilience, as do species rising in California, and throughout the Caucasus too. The holm and chestnut-leafed oak, in addition to the Persian ironwood and hornbeam, ought to all do nicely. However timber dwell for 500 years plus — it’s laborious to foretell what circumstances will likely be like to date sooner or later.

Kevin Martin is head of tree collections at Royal Botanic Gardens, Kew

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