Leyland cypress

Leyland cypress: facts and stories

The Leyland cypress is a Frankenstein tree that came about from human manipulation and landscaping with species that wouldn’t usually come into contact with each other. The resulting hybrid species has now completely escaped its creators and spread far and wide.

At the end of the 19th century, it was fashionable at large British estates to plant cypress trees. The upper classes were seduced by these trees with their beautiful, dark green, highly dense foliage, as well as their slender silhouettes. Two varieties were used in hedgerows, namely the Nootka cypress and the Monterey cypress. The former was known for its hardiness, while the latter was appreciated for its rapid growth.

In the wild, these two species would normally grow more than 1500km away from each other in different settings. They wouldn’t normally have come into contact with each other, but they were mixed into the same hedgerows to create elegant boundaries at banker Christopher Leyland’s estate in England. No one imagined that the Nootka and Monterey cypresses would pollinate each other and lead to a giant new variety of cypress: the Leyland cypress, Cupressus × leylandii.

During the 1970s, millions of people in Britain planted Leyland cypresses as hedges in their gardens, not knowing how big they would grow in only a few years! When left to grow as it pleases, a Leyland cypress tree will grow up to 1m in height per year, and can reach heights of up to 35m. Today, the number of Leyland cypress trees is said to at least match the population of the United Kingdom. Due to their size, these trees are the cause of numerous conflicts between neighbours.

Did you know?

During the course of their evolution, cypress trees have adapted to be resistant to fire (known as pyrophytes). Due to regularly coming into contact with fires in their native habitats, they have grown able to tolerate flames.

One of the secrets to them resisting fires is their ability to eject the flammable substances contained within them in the presence of high heat. They release their essential oils (terpenes), alcohols and other combustible substances into the air in the form of molecules that can fly away.

These molecules get blown hundreds of metres away by the wind, which triggers a second secret ability: cypresses downwind from the first trees detect the release of these molecules in the air. This acts as a warning signal for them to also eject all of their flammable substances as well. When the fire eventually reaches these cypresses further downwind, all that’s left are large columns of water with no combustible substances left to burn.

The benefits of cypress trees

Cypress trees are rarely seen in the city. They are sometimes planted for their beauty and decorative character. Originating in North America and the Mediterranean, they help with diversifying the classic range of trees in the city.

Their small leaves (scale-like sprays) aren’t as productive as ‘classic’ leaves, but the benefit here is that they are kept all year round. As long as temperatures stay above freezing, cypress trees will produce oxygen throughout the year. They capture large amounts of CO2 and store it sustainably in their wood.

How to recognise a Leyland cypress tree

Leaves

Small scale-like sprays (1–2mm); dark green (matte); do not fall from the tree all at the same time

Foliage

Always present on the tree (evergreen)

Fruit

Sphere-shaped cones (2cm), brown-red in colour

Bark

Brown; comes off in long strips with age

Specifics about this tree

This tree is remarkable in multiple ways.

Firstly, it is part of the group of rare trees growing in Parc Tenbosch, which is like a pocket-sized arboretum. This spot of unique diversity within Brussels is in the process of being classified as part of the living heritage of Ixelles and the greater region.

So far, this is the only Leyland cypress on the region’s inventory of remarkable trees. It is a very rare specimen. Its size is impressive. Contrary to others of the same species which were planted in hedgerows, this tree doesn’t get pruned and cut back twice a year; instead, it seems to be growing quite freely. And it hasn’t finished growing yet!

Still stretching higher and higher into the sky, it was planted right here in the middle of the park to make a mark on the landscape. Surrounded by the park’s extremely dense vegetation, this Leyland cypress stands out and makes its presence known much more than many of the surrounding trees.

(Story and photos created by Priscille Cazin- Sylvolutions)

This portrait is:

- Enriched with an illustration from the Belgian Federal State Collection on permanent loan to the Meise Botanical Garden.

- An initiative of Christos Doulkeridis, Mayor of Ixelles , Audrey Lhoest, portfolio holder for Environment, Green Spaces and Planting, and Tourism and the Ixelles Communal executive