This is an expanded version of an article published in the winter 2017-18 edition of London Wildlife Trust‘s Wild London magazine
As autumn draws to a close, the bare branches of trees stark against wintry skies, we find ourselves on the tail-end of a mast year for London’s acorns. Mast is another name for nuts or seeds, with beech nuts often referred to as ‘beech-mast’. It means a time when the weather and temperatures in spring and summer have created the right conditions for a bumper crop.
Oaks are wind-pollinated, one of nature’s first reproductive mechanisms for plants that evolved very early on land with the arrival of spore-bearing mosses hundreds of millions of years ago. Trees like cherry and others in the rose family, are pollinated by bees, butterflies, moths and flies.
Though cherries are far tastier than acorns, the oak’s fruit is one of the most important to us for several reasons. When acorns fall many of them will simply fail in the leaf litter or decay away to feed the soil. Birds like jays will stash acorns and plant thousands of them to keep them alive over the winter. Grey squirrels do exactly the same.
If you think about it, and scientists have been, this is one of the most important vehicles for woodland creation on Earth. It’s also one of the reasons that oak woods were able to recolonise the Northern Hemisphere after the end of the last glacial period some 12-14,000 years ago.
If any of those jays died or forgot some of their acorns, they sprouted into trees and woods, many of which would eventually form great woody landscapes adapted and exploited to what we now know as the Great North Wood, Epping Forest, the Weald and the New Forest.
In North America there were entire cultures of Native Americans who built their lifestyles on a diet of acorns. Beneath their shells acorns are nuts that can be ground down for flour, coffee or even jelly.
In Britain the hazelnut is one of the single most important food sources for our species, especially before the advent of farming when hunter gatherers relied on foraging to survive. Archaeologists have found regular evidence of hazel nut shells at prehistoric settlement sites, sometimes in vast numbers. There is also evidence that our ancestors cooked hazel into a paste that could be taken on long journeys.
But perhaps the most fascinating cultural impact of the acorn is when it is missing, and in its place a parasite. In the spring tiny parasitic wasps appear from galls, a growth (sometimes referred to as a tumour) that has prospered in the place of an acorn, and lay their own eggs in an acorn bud. A chemical reaction takes place in the tissue of the plant and a gall is formed.
There are many species of gall, and many of them are not instigated by solitary wasps, but one of the most significant for human civilisation is that of the oak apple gall.
The oak apple gall was imported to Britain over a 1000 years ago for its prime use in the creation of ink. The galls can be ground down and mixed with chemicals to make a black ink. It was this ink that was used to write almost all of the major doctrines and political agreements in the western world.
The Magna Carta and the American Declaration of Independence are but two of them and, indeed, that sylvan scripture known as the Forest Charter of 1217 will also have been transcribed in oak ink. Amazingly, it was only in the 1970s that the German government stopped using oak gall ink for use in all official documentation.
Knopper galls in summer
London’s other notable seeds are those of horse chestnut, beech and sweet chestnut. Horse chestnuts, named after the horseshoe-shape at the base of the leaf stem or petiole when plucked from a branch, are not related to sweet chestnuts. Neither of these trees are deemed native to the United Kingdom, and sweet chestnut sits in with the oaks in the beech family.
If you roasted chestnuts on an open fire at Christmas it will be those of the sweet, not the horse chestnut. Sweet chestnuts are the fruit found inside painfully spikey shells, very similar to the horse chestnut.
For the more childish among us, the horse chestnut is really known as the conker tree. The sight of a glossy brown conker in roadside leaf piles in autumn is a thing of wonder. The maple family’s seeds may not be palatable, but the game of ‘helicopters’ was one of great pleasure for school children before the arrival of smartphones.
Though we often focus on the edibility of plants and their fruit and seeds, the crops of trees like rowan, oak and beech have an impact on the activity and behaviour of birds in autumn. In October there can be seen large movements of jays, with birds acting quickly to secure seeds and plant them in a suitable location.
A jay massaging its way high across an open field, heading to and from an oak or beech wood, is a common sight in the early autumn. Redwing, a winter arrival in the UK, rely on rowan’s bright red fruit. Changes in the Scandinavian crop can trigger the movements of this species south as winter draws in.
Where old, fruit-packed hedgerows still exist in the UK, heavy with rosehips, haws and holly berries, redwings can be found feasting. From places as far apart as rural moorland and urban London, their distinctive but subtle tseep calls can be heard overhead at night.
Those nocturnal calls can be a pleasant reminder of the changing season, of the fundamental need for fruit and seed for the wild and civilised alike.