© 2014 by Barbara Copperthwaite.

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Our most welcome immigrant

The fat, sticky buds of winter, the downy green leaves of spring, the shiny brown conkers of autumn: the horse chestnut seems to have a new face for every time of year, a face which perfectly encapsulates that time.

   Yet it might surprise some to discover it is not a native to this country. The horse chestnut, which lives for up to 100 years, originally grew wild in hilly regions of Greece, Bulgaria and Iran, before being introduced to Britain in the 17th century.

   Since then it has been widely planted as an ornamental tree in gardens, parkland and often on long avenues, as well as in and around fields, to provide shade for farm animals. The foliage is palatable to cattle and horses, which stretch to eat all the leaves they can reach while sheltering beneath it.

   A curious feature of the horse-chestnut is its slowness to establish itself in the wild, despite its apparent adaptability. It is a hardy tree able to grow on most soils and its seeds (the conkers) germinate freely, yet it seems unable to compete easily against many of our native plants, which often crowd it out. This is in stark contrast to other introduced species such as sycamore, which spread rapidly into woods and plantations.

   It is impossible to confuse the horse chestnut with any other tree, including the totally unrelated sweet chestnut, which is clearly distinguished by its yellow flowers, long, saw-edged leaves, more spiny fruit cases and spirally-twisted bark. The horse chestnut’s own grey-brown bark is initially smooth, and becomes rough and scaly with age. 

   No matter the season, the horse chestnut is always impressive to look at. With its 

   When the tree is in full leaf it forms a dense, shady canopy which shows beautifully how leaves can be arranged to reap the maximum benefit from incoming sunlight. In fact, the leaves can twist on their stalks during the day, and position themselves to catch the sun, so cleverly avoiding being overshadowed by their neighbours.   

   The flowering spikes, or candles, blossom in Mid-May, although they emerge earlier, with the young leaves. Each candle bears up to 100 male or bisexual flowers. Made up of four or five petals, the white flower is tinged with yellow blotches that turn red after the flower is pollinated. Hard-working bees pick up and transfer pollen from each flower to the stigmas that protrude from each flower to the stigmas of other flowers.

   As autumn approaches, conkers form inside a tough, spiky capsule, and are protected by a lining of soft white padding; a jewel nestling inside a well-protected jewellery box. As they ripen they change from white to a rich, glossy brown by early October. If they do not fall with the capsule, or are not knocked down with sticks thrown by children, they will be released as the three segments that make up the capsule dry and peel away from the seeds. Even in this age of high definition games played on powerful consoles, there seems to be something irresistible about playing conkers – a game first popular in the 19th century.

   With its conkers all shed and the weather cooling rapidly in autumn, the horse chestnut which so eagerly heralded spring is once again one of the first trees to respond. Its leaves are among the earliest to colour and fall in autumn, changing to yellow and deep gold before dropping.

   Is there a tree that more evocatively illustrates the ever-changing wheel of this country than our welcome immigrant, the horse chestnut?

wide-spreading branches and typically rounded crown, it presents a towering  mass of luxuriant foliage throughout the summer and a glorious blaze of colour in autumn.

   The magic begins with its sticky buds. They form during  the previous summer, and are coated in a shiny resin that protects the new season’s shoots from attack by insect pests.

   The tree’s secret weapon gums up these insects, immobilising them and preventing them from chewing into the delicate buds.

   In early spring the buds swell and break open on the tree, the bud scales peeling back as the growing tip emerges. The young leaves are a pale but vibrant green, and clothed in white, furry down which gives protection throughout the winter (the down is soon shed as the leaves expand). Large horseshoe-shaped scars on twigs are where the previous leaf stalks were attached.

   The leaves are among the first of any tree to appear in spring, and can grow to be up to 20cm (8in) across.

   They are the largest leaves of any found in Europe, and are made up of five to seven pear-shaped leaflets borne on a long, stout stalk.

   

Perhaps more than any other tree the horse chestnut vividly reflects the changing seasons of Britain…