Wych elm (also known as Scotch elm or Scots elm) is a large deciduous tree often with multiple large branches coming off the main trunk which give it a broad, spreading crown. The leaves have a characteristic asymmetrical base, a characteristic of wych elm, and taper to a sudden point at the top. They are serrated with tiny hairs on the underside and change from dark green to yellow in the autumn.

Behaviour

Wych elm prefers rich and well-drained, loamy soils and grows in elevations from sea level up to over a 1000m. In Britain, seedlings of wych elm are found up to 300m. It thrives in moist forests with rich soils and high humidity, or in groves along streams, but rarely in very wet or flooded areas. 

Wych elm is one of the few species of elm to spread mainly by seed, instead of propagating clones from root suckers. Flowers appear in early spring, well before the new leaves open out. The flowers are dark reddish-purple in colour and produced in clusters of 10 to 20, spaced out along the twigs and small branches. They are hermaphroditic, meaning that the organs for both sexes occur in each flower. Pollinated flowers grow to become fruits called samaras, which are ovoid in shape with a small notch at the end. The seed is in the centre of the samara, the ‘wing’ surrounding it on all sides. The samaras are initially a light green colour, turning brown as they ripen, whilst the seed itself often turns pink on reaching maturity. They are shed from the tree in early July and carried on the wind. 

Size

• Height: typically 15 – 20m in Scotland; can reach 30 – 40m, but this is rare Scotland.
• Lifespan: 40 – 60 years; believed to reach an age of 400 years.

Status

The range and abundance of wych elm in Scotland has been reduced in recent decades by the spread of Dutch elm disease. As a result, wych elm is now less common in the UK and is classified as vulnerable within Europe according to the IUCN Red List of European species. In Scotland, future conservation of the wych elm seems, paradoxically, likely to be based on replacement with alternative non-native species and hybrids.

Distribution

Wych elm occurs throughout much of Europe, but is concentrated in the more northern regions. Wych elm is now recognised as the only species of elm that is definitely native to the UK. It occurs throughout Scotland growing naturally as far north as Sutherland and Skye, but is scattered. It is not, however, native in the Outer Hebrides, Orkney or Shetland.  

When to see

Year-round. Purple-brown flowers open around March/April; leaves begin to appear from late April and are fully expanded by early June. In winter, the tree is easily identifiable as both bud and twig are densely covered in orange hairs.

Facts

• Wych elm has been growing in Scotland for around 9,000 years. We know this from radiocarbon dated pollen extracted from bogs and lake sediments. 

• Wych elm’s timber is almost impossible to split and resistant to water. Before metal was widely available, many towns had elm water mains, including Bristol, Reading, Hull and Liverpool.

• Wych elm has a number of medicinal uses, such as treating diarrhoea and other stomach ailments. The bark of the tree can also be stripped and heated to treat wounds, skin ulcers and eczema.

• The UK National Tree Seed Project launched by Kew’s Millennium Seed Bank in 2013 now contains 52 collections of Wych Elm seeds, totalling more than 309,000 seeds.  As banked seeds will survive for many decades they provide a vital benchmark of the genetic diversity in this tree population.

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