Scotch laburnum

Scotch laburnum: how do you recognise it?

Habit

Small tree, often multi-stemmed, with a rounded to vase-shaped crown; up to about 6 m tall and 5 m wide.

Leaf

Three-part, with elliptic leaflets of 4–8 cm; glossy dark green and almost hairless underneath.

Flower

Golden-yellow pea flowers in long, slender, hanging racemes in May–June, sweetly scented.

Fruit

Flat, smooth pods containing dark seeds, which can stay on the tree into winter.

Bark

Smooth and greenish brown; the heartwood is dark and very hard.

Flowering: May–June · Plants: March–April and October–December · Pruning: July–August

Why grow it?

• A spectacular yellow display in May–June, with slender hanging racemes of up to about 30 cm.
• The flowers have a sweet scent, stronger than that of common laburnum.
• Bees and bumblebees are drawn to the flowers.
• Very hardy and happy on chalky soil.
• Small enough for an ordinary garden, as a specimen or over a path.

Scotch laburnum: where does it grow best?

• Sun or partial shade; it flowers most freely in full sun.
• Any well-drained soil: sand, loam or clay, neutral to chalky.
• Moist; it does not tolerate waterlogging.
• Do not plant it near a play area, a chicken run or a field with grazing animals: the seeds are highly poisonous.
• Allow about 5 m of space.

Light

Sun and partial shade

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Normal

Size

6 m tall, 5 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Wisteria: Flowers at the same time; together over a pergola they combine yellow and bluish purple.
• Ornamental onion: Purple globes beneath the yellow racemes, a classic picture.
• Columbine: Flowers in the same weeks in the light shade beneath the crown.
• Bearded iris: Blue or purple irises intensify the yellow in May–June.

Scotch laburnum: when and how to plant it?

Plant in March–April and October–December.

1. Plant in March–April or from October to December, when the soil is not frozen or waterlogged.
2. Dig a hole twice as wide as the root ball and loosen the bottom; on heavy clay, mix in some coarse sand.
3. Set the tree at the same depth as it was in the pot: the root collar stays at soil level.
4. Give a young tree a sturdy stake on the windward side: in the first years it is easily blown askew.
5. Firm the soil well and water straight away with a few buckets.
6. Spread a mulch around the base, without touching the trunk.

Care

Water

In the first year, water regularly in dry spells. After that it is rarely needed.

Feeding

Usually unnecessary. Too much fertiliser gives lots of leaves and fewer flowers.

Spent racemes

Cut them off after flowering, before the pods ripen: this prevents poisonous seeds in the garden and spares the tree.

Stake

Check stake and tie every year and keep a young tree staked for two or three years.

Seedlings

Weed out seedlings that come up under the tree straight away.

Tip: Cut off the spent racemes before the pods ripen: you spare the tree and avoid poisonous seeds in the garden. Plant it where you can see the hanging racemes from below, for example over a path.

Scotch laburnum: when to prune it?

Pruning months: July–August.

When: Prune in summer, in July–August: it bleeds least then and the wounds close before winter.

How:

• Cut off spent racemes and young pods before they ripen.
• Remove dead, damaged and crossing branches.
• Remove shoots at the base of the trunk.
• Do not cut thick branches: large wounds heal poorly.

Caution: Wear gloves when clearing pods and prunings, and never throw them into a chicken run or field.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Soak the seed overnight in warm water and sow in autumn or spring in a pot. Keep seed out of children’s reach. Seedlings only flower after several years.

Grafting

Cultivars and the hybrid ‘Vossii’ are grafted in nurseries; it is a job for professionals.

Scotch laburnum: how does it get through the winter?

Hardy to −30 °C.

• Very hardy, to about −30 °C: no protection is needed in Belgium.
• Wet, heavy soil in winter is a greater danger than frost.
• Check young trees after a storm: straighten a tree that has been blown askew and tie it in again.
• Remove any remaining pods in winter, when they are easy to see.

Diseases and pests

• Laburnum leaf miner: Brown blotches in the leaves caused by the caterpillars of a small moth. Rarely harmful: clear up affected leaves in autumn.
• Honey fungus: The tree suddenly dies back, with white fans of fungus under the bark and toadstools at the base in autumn. Remove the tree with as much root as possible.
• Seedlings: Young laburnums come up under the tree. Pull them out young and cut off the pods in time.
• Leaning: Young trees are easily blown askew. A sturdy stake in the first years prevents this.
• Poor flowering: In too much shade or after heavy feeding it flowers poorly. Give it more light and do not feed.

Through the year

• January: Dormant. Remove any remaining pods.
• March: Plant. Check the stake.
• April: Plant. Water young trees in dry spells.
• May: Flowering begins with fragrant yellow racemes.
• June: Flowering. Enjoy the scent.
• July: Cut off spent racemes and young pods. Prune dead or crossing branches.
• August: Finish any pruning. Remove remaining pods.
• October: Plant. Clear up fallen pods and leaves.
• November: Plant.
• December: Plant in mild weather. Remove any remaining pods.

Edible and useful

Not edible. All parts of laburnum are poisonous, especially the seeds: the pods look like those of peas or beans and are a classic cause of poisoning in children. Do not plant it where small children play, or cut off the faded flower trails before they form pods. Also poisonous to horses and dogs. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• Despite the name Scotch laburnum, it does not come from Scotland but from the mountains of central and southern Europe; it was, however, planted widely in Scotland from early on.
• The well-known laburnum ‘Vossii’ is a hybrid between Scotch laburnum and common laburnum. It has long racemes and sets little seed.
• The dark, hard heartwood of laburnum was once used for inlay and turning, as a substitute for ebony.