Liquidambars – Autumn Stunners!
Down in the Pinetum early starters have already begun the run in to winter with the leaves of the deciduous trees and shrubs beginning to fall. This is one of the most magical times at Bedgebury as the leaves start to change from greens to a blaze of yellows, reds, oranges, and purples. It is now that one of my favourite trees, the American sweetgum, Liquidambar styraciflua, comes into its own and takes centre stage.
The group of Liquidambars in Dallimore Valley provide some of the best autumn colour I have seen anywhere in the world. What I love about these trees is the amazing range of colours you get on the same tree, with individual leaves ranging from yellow though orange to red, dark brown, purple and even black. Unlike their more famous look-a-likes, the Maples, Liquidambars seem to retain their leaves for longer giving a more impressive and enduring display.
There are four species of Liquidambar which can be found in Asia (China, Taiwan, Laos, Korea and Vietnam) South West Turkey, Rhodes and a large swathe of Eastern North and South America from New England to Nicaragua. They are a tree species that can reach up to 40m in height in their natural forest habitat. For many years they were included in the family Hamamelidaceae (the Witch Hazel family) but recent genetic studies have put it in the family Altingaceae.
The resin of liquidambar has had many uses. American sweetgum resin is an ingredient in ‘Friar’s Balsam’, a commercial preparation used to treat colds and skin problems. It can also be used to make chewing gum and in traditional medicine has been used to treat topically for anxiety, bronchitis, catarrh, coughs, cuts, ringworm, scabies and stress-related conditions. It is from this resin that the genus gets its name, Liquidambar.
Superficially liquidambars resemble maple trees because of the shape of their leaves but it is easy to differentiate them by their fruit. Maples have winged “helicopter” fruits and liquidambars have spiky round ball shaped fruits that contain the seed. These round fruits have been given a variety of fabulous names like “space bugs”, “monkey balls” or “bommyknockers”. To further distinguish between them, in maples the leaves are opposite each other on the shoots, but with liquidambar the leaves are offset and held singly. The cork-like bark of the sweetgums is also a distinctive feature.
In cultivation, liquidambars are grown predominantly for their distinctive star shaped leaves and stunning autumn colour. They seem to be quite adaptable, growing in a range of sites at Bedgebury from dry through to damp and in a range of soils with variable PH levels. However they seem to thrive and colour better on the slightly less acidic and moister soils in Dallimore Valley. At Bedgebury we have all four species of liquidambar and a number of cultivars of varying ages and sizes.
Liquidambar acalycina (Chang’s sweetgum)
The group of liquidambars in Dallimore Valley provide a blaze of autumn foliage which is on a par with the best in the world. This species is the most recent introduction to the UK, brought from its natural habitat in the mountains of southern China in the 1980s. This species is starting to make its way into the nursery trade but is still uncommon in tree collections. It is similar to Liquidambar formosana but is hardier and more robust in growth. Unusually it has a better spring and summer foliage colour than it has in autumn. Our two specimens were donated to us by Lime Cross Nursery and were planted in 2010.
Liquidambar formosana (Chinese sweetgum)
This species differs from the others because it has 3 lobed leaves rather than 7 or 5. It is slightly more tender than the others and can be damaged when we have severe winters. However it is still worth growing for its autumn colour and also has a beautiful purple colour to its new growth flush. Our oldest specimen was given to us by Westonbirt Arboretum and was planted in 2004.
Liquidambar orientalis (Oriental sweetgum)
With a natural distribution in south west Turkey and Rhodes this is the rarest of the Liquidambar species. Its current natural environment is estimated to be only 1,500ha, lower than the estimate in the 1940s of 6,000 -7,000ha. This decline has led to it being listed as “Vulnerable” by the International Union for the Conservation of Nature. Its natural forest home has been badly degraded by the over-exploitation of Balsam. The “tapping” for the valuable resin “wounds” the trees. In the wild, the largest trees can reach 35m in height but in the UK it remains an ornamental, small, bushy tree with yellow or red autumn colour. Our oldest specimen was bought from Birchfleet Nursery and was planted in 2000; we also have two specimens that were collected as seed from the wild trees in Turkey.
Liquidambar styraciflua (American sweetgum)
This is by far the most common of the species in cultivation; at Bedgebury it makes a round headed tree about 20m in height and it is probably the most stunning of all our trees during the autumn colour season. The glossy green leaves start to turn towards the end of October and it is the range of colours they produce, often simultaneously, which makes them so outstanding. American sweetgum timber has a fine grain and is one of the most important sources of decorative plywood panels. It can be polished, stained and used for veneer as a cherry, mahogany or walnut substitute. It can even be dyed black and used as an ebony replacement for picture frames. However the timber is brittle and not generally used for structural purposes. Over 23 specimens can be found in the Pinetum of varying sizes and ages. At the moment the biggest and best specimens can be found in Dallimore Valley but as the younger trees grow they will add to and enhance the wonderful tree collection at Bedgebury. I have been lucky enough to see all the liquidambar species in the wild, either whilst collecting seeds in West Virginia, attending a red-listing workshop in Tianmu Shan in China or by stopping the airport shuttle bus whilst on a family holiday in Turkey! If you don’t get a chance to see them in the wild I hope you get a chance to enjoy them in the Pinetum this autumn and throughout the year.