Laburnum alpinum Seeds | Scottish Laburnum

Scottish laburnum hung with long golden-yellow pea-flower racemes in late spring — Scottish Laburnum (*Laburnum alpinum*): Fabaceae, the later-flowering, longer-racemened laburnum of the southern European mountains.

LATIN NAME: Laburnum alpinum

COMMON NAME: Scottish Laburnum

Plant Profile

Scottish laburnum is the mountain form of the golden chain tree, and it differs from its better-known relative in ways that matter in a short-season garden. It is a small deciduous tree, four to seven metres, with smooth olive-green bark, dark green three-leaflet leaves that are hairless beneath, and a round, open crown.

The flowers are the reason it is grown: long, pendulous racemes of yellow pea flowers, twenty-five to forty centimetres long and noticeably longer than those of the common laburnum, opening two or three weeks later and lasting longer in cool weather. The pods that follow are flattened and hairy, and the seeds inside are black and hard. Every part of the plant, and especially the seed, contains cytisine.

Science & Biotechnology

Cytisine is a quinolizidine alkaloid that binds to nicotinic acetylcholine receptors, and it is the reason laburnum is dangerous: a handful of seeds can make a child seriously ill, and the poison acts quickly, with vomiting, dizziness and in severe cases convulsions. It is also the reason the plant is pharmacologically interesting, since cytisine has been developed as a smoking-cessation drug in eastern Europe. The toxin is concentrated in the seed and persists in the pods and wood.

Laburnum alpinum and Laburnum anagyroides hybridise where they meet, and the intermediate is grown as Laburnum x watereri, of which the cultivar Vossii is the one usually sold, with racemes up to fifty centimetres. The mountain species is hardier and later, which makes it the safer choice where late frosts cut the common laburnum’s display. The wood is exceptionally hard and dark, and it takes a fine polish.

Uses & Benefits

Laburnum was a favourite ornamental in nineteenth-century gardens, planted over arches and along pergolas so that the chains hung down to head height, and it is still one of the most spectacular small trees in late spring. It is best used as a specimen or trained over a sturdy pergola, not in a garden where small children play unsupervised, and the pods should be picked off and binned if children or pets have access.

The wood is the other reason the tree has a history. Dark, dense, close-grained and capable of taking a high polish, it was known as false ebony and used for inlay, turnery, knife handles and the best veneers, and it is still valued by cabinetmakers who can get it. The tree is short-lived by tree standards, often thirty to fifty years, and old specimens become hollow and brittle, so it should be replaced before it fails.

Growing from Seed

The seed coat is hard and should be scarified: pour hot water over the seed and leave it to cool overnight, or rub it with sandpaper. Sow in a light compost at about twenty degrees; germination is usually quick and heavy, sometimes within ten days.

Grow the seedlings on in pots for two years and plant out in autumn, in any well-drained soil in full sun. The tree resents root disturbance and should not be moved once established, so choose the site carefully. It also suckers if the roots are damaged, and it is best staked for the first few years because the wood is brittle and the crown catches wind.

Our Take

The finest golden-chain tree for a cold garden, and one that demands respect for its seed. Plant it where children rarely go, and enjoy the chains for thirty years.

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