PURPLE FOR ROYALTY

A beloved monarch

On the rue du Cens in Ganshoren, there is a little square that shelters an immense copper beech. Of course, it might be better to put it the other way around, as its vast canopy of dense foliage overhangs virtually the entire space. This great dome is supported by a trunk that is more than 5 metres around. Some of its branches gently shade a MIVB/STIB bus stop. The waiting commuters seem oblivious to its presence.

The older neighbourhood residents, on the other hand, are well aware of the value of this beech. They remember that it became listed in 1949: ‘which is relatively rare for a tree, no matter how remarkable. Nevertheless, this distinction proves that the municipality and local inhabitants were already highly attached to it at the time. The neighbourhood residents above all love its colour. Apparently, copper beeches, also known as purple beeches, are rarer and more fragile than common beeches, which grow abundantly on the other side of the city, in the Sonian Forest, for example’.

For a long time, our beech grew in a garden. All of the plantings around it were preserved when the square was laid. And an enclosure was created tracing the circle of its crown to provide it with plenty of rich, airy soil, similar to that of the forest: with low-growing vegetation and a carpet of leaves that generates a light layer of humus.

A natural flamboyance …

The reddish colour is not uncommon in hardwoods. It appears in young leaves in the spring. It is caused by coloured pigments that range from red-orange to purplish blue: anthocyanins. They serve as a shield against the sun's ultraviolet rays, much like sunscreen does for us. Later, an enzyme destroys the red pigments once the leaf no longer needs their protection.

But not in the case of the copper beech: they lack this enzyme. It’s a rare genetic mutation that occurs in beech seeds. Only 1 to 3 seeds out of every 100 will naturally result in purple foliage. As we humans are fascinated by all that is rare, we have sought to reproduce this characteristic, and to obtain the most intense colouring possible. All copper beeches are descended from a single individual, discovered around 1680 in the Hanleiter Forest in Germany, which was still alive in 1910. Created by grafting a branch of a beautiful deep-red specimen onto healthy rootstock of the common beech: they all have a scar on their trunk to show for it.

But if you look for the traces of the graft on the beech on the rue du Cens, you won't find it. That’s because the purplish-red hue of its foliage is the result of the genetic make-up of the seed from which it grew, making it one of the rare wild specimens that is naturally purple in colour.

Common beech ancestry

Aside from its flamboyant foliage, however, in every other way, this giant is every inch a classic beech.

Its trunk is silver grey. Its base somewhat resembles an elephant’s foot. There are cracks in its bark: it has had to slowly adapt to the immense circumference of the trunk. These ‘wrinkles’ are a sign of age: it is well over 200 years old. In its youth, its ‘jacket’ was particularly fine and smooth. That’s because in young beeches, the bark is rapidly renewed. Their greyish ‘skin’ is the feature that makes the species easy to identify. For an idea of what it looked like when it was young, simply look up at the branches.

One detail might catch your eye. The twigs bearing the buds are long and spiky, with the pointed buds clad in chestnut brown/rust coloured scales. It is said that the forest elves sharpen them and use them to hunt slugs. In the spring, these buds open into oval, smooth-edged leaves. When they are still young and tender, they can be added to salads. They have a slightly tangy flavour.

Later, just like the common beech, the tree grows beechnuts. They are rounded capsules bristling with fuzzy spines that split open to release brown seeds. They can be peeled and eaten, much like pine nuts. Long ago, beechnuts were part of the human diet. They were soaked in water to reduce their tannin content and make them more digestible. Roasted beechnuts were delicious. And they could be pressed to produce oil. Today, these flavours are being rediscovered thanks to the trend for foraging wild edibles.

A well-buttressed water tower

If you pass by after it has rained, you will see large, dark, wet trails all along the trunk. The foliage of the beech collects the water. Its leaves, twigs and branches are positioned in order to capture as much of the water droplets as possible and to channel them down to the roots. Peter Wohlleben explains the genius of the tree in his book The Hidden Life of Trees (1): ‘Their crowns serve as much to expose the leaves to sunlight as to intercept and redirect the rain. The water falls on hundreds of thousands of leaves from where it drips on the twigs. It flows along the branches where the tiny streams meet and form a torrent that runs down the trunk. At the bottom of the trunk, the current is so strong that the water churns when it hits the ground. During a heavy rainstorm, an adult tree can store up to 1000 litres of additional water. Channelled directly to its roots thanks to its architecture, this extra water infiltrates the earth where it will be used to withstand one or more dry spells.’

Let your eyes follow these long rivulets all the way down to the foot of this ‘water tower’. Its base appears especially solid: slightly curved columns mark the transition between the trunk and the roots. These areas of strong growth are called buttresses: recalling the monumental architecture of mediaeval castles. They provide the tree’s stability. They are also useful if you want to get an idea of the direction in which the roots probe the earth just a few centimetres beneath your feet. As the soil has been eroded by the busy traffic on the square, the roots are occasionally visible above the surface of the ground as well. The roots of the beech trace the outline of its form: they grow no deeper than a shallow layer but form a highly dense structure directly beneath the crown, a bit like the foot of a wine glass keeps it stable.

Unfortunately, this stability is somewhat vulnerable to a mushroom that attacks the tree’s root system. It takes advantage of the wounds of emerging roots and the cracks in the mature bark to take hold at the foot of the tree. In autumn, the fruiting bodies of this ‘tenant’ are impressive: called the giant polypore, it progressively eats away at the foot of the colossus. The Region and the municipality are monitoring it closely to ensure that the tree defends itself properly against the fungus and remains in good health. After all, we all want to see this flamboyant, regal individual stay at the heart of the neighbourhood for many years to come.

(Story created by Priscille Cazin https://www.sylvolutions.eu Photos by Gwen Breuls https://vimeo.com/gwenvideos)

More info

(1) Peter Wohlleben, The Hidden Life of Trees, p116, Greystone Books.

This portrait is enriched with an illustration from the Belgian Federal State Collection on permanent loan to the Meise Botanical Garden. See attached. Thanks to the library (heritage collection) for this contribution. https://www.plantentuinmeise.be/en/home/
as well as a photo of a remarkable purple beech from the Beltrees collection https://www.arboretumwespelaar.be/EN/