Common laburnum

Common laburnum: how do you recognise it?

Habit

Small tree or large shrub of 4–8 m, often multi-stemmed, with an open crown.

Leaf

Alternate, with three elliptic, untoothed leaflets 3–8 cm long on a long stalk; underside grey-green and silky-hairy.

Bark

Smooth, olive-green to brownish green; young twigs grey-green and hairy.

Flower

Hanging clusters 10–30 cm long of golden-yellow pea flowers, in May–June.

Fruit

Flat, hairy pods 4–6 cm long with black seeds, which stay on the tree for a long time.

Difference from Voss’s laburnum

Voss’s laburnum (Laburnum × watereri ‘Vossii’) has even longer clusters (up to 50 cm), less hairy leaves and few pods; it is the most widely planted garden form.

Difference from Chinese wisteria

Wisteria is a climber with pinnate leaves and bluish-purple flower clusters.

Flowering: May–June · Pruning: July–September

Identify by feature: Yellow flowers in spring · Hanging flower clusters · Pods

Looks like it, but isn’t

• Voss’s laburnum (Laburnum × watereri ‘Vossii’): even longer clusters (up to 50 cm), less hairy leaves and few pods; the most widely planted garden form.
• Chinese wisteria Wisteria sinensis: a climber with pinnate leaves and bluish-purple flower clusters. Difference from Chinese wisteria

Why grow it?

• Long clusters of golden-yellow flowers in May–June.
• Small enough for an ordinary garden, and can be trained over an arch or pergola.
• Flowers for bumblebees and bees.
• Fixes nitrogen and grows on almost any soil.

Common laburnum: where does it grow best?

• Sun to partial shade; it flowers best in sun.
• Any well-drained soil, including chalky or poor soil; no wet feet.
• Allow 4 m width: suitable for an ordinary garden, but not where young children play, nor next to a field with horses or livestock.

Light

Sun or partial shade

Legal basis

Any garden soil

Moisture

Normal

Size

6 m tall, 4 m wide

Hardiness

Throughout Belgium, no protection needed

Goes well with

• Chinese wisteria: Flowers at about the same time, in May: together over a pergola or arch, a picture in gold and bluish purple.
• Common lilac: Fragrant purple or white flowers in May, next to the yellow of the laburnum.
• Ornamental onion: Purple globes beneath a laburnum arch: a classic sight in May.

Common laburnum: when and how to plant it?

1. Plant from November to March, root-balled or container-grown.
2. For the garden, choose the hybrid ‘Vossii’: longer clusters and far fewer pods – though it is just as poisonous.
3. Put a sturdy stake on the windward side and water well after planting.
4. For a laburnum arch: plant young trees on both sides of a sturdy frame and tie the branches in along the arch.

Care

Watering

In dry spells during the first year; rarely needed after that.

Feeding

Not needed: it fixes its own nitrogen from the air.

Spent flower clusters

Cut them off as soon as they fade, before they set seed: this spares the tree and prevents poisonous pods.

Laburnum arch

Tie new shoots to the frame regularly and cut back anything that sticks out; wear gloves.

Tip: Want a laburnum arch without needless risk? Choose a spot well away from play areas and fields, plant ‘Vossii’ and cut off the spent flower clusters every year.

Common laburnum: when to prune it?

Pruning months: July–September.

When: After flowering, in summer (July–September).

How:

• Prune lightly; large wounds heal slowly.
• Cut off spent flower clusters before they set seed: this spares the tree and prevents poisonous pods.
• Remove dead, crossing and overlong branches, cutting back to a side branch.

Caution: Wear gloves and clear away all prunings: the branches, leaves and bark are poisonous too, and must never end up in a field or near animals.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Sowing

Soak the hard seeds overnight in warm water and sow them in a pot in spring; wear gloves, as they are highly poisonous.

Grafting

The hybrid ‘Vossii’ is grafted by the nursery.

Common laburnum: how does it get through the winter?

Hardy throughout Belgium: no protection needed.

• Fully hardy.
• In winter pods often still hang on the tree: cut them off wherever children go.

Diseases and pests

• Poisonous pods: To children, the pods and seeds look like peas. Cut off spent flower clusters in good time and pick up fallen pods.
• Laburnum leaf miner: Brown blotches in the leaves, with tiny larvae between the leaf layers. Harmless to the tree; clear up fallen leaves.
• Honey fungus: Dying branches, white fungal sheets under the bark at the base of the trunk and toadstools in autumn. There is no cure: remove the tree with as many roots as possible.

Through the year

• March: Last month for planting.
• May: Flowering: long yellow clusters full of bumblebees.
• June: Flowering ends: cut off spent clusters before pods form.
• July: Prune after flowering; tie new shoots in along the arch.
• August: Pruning still possible; pick up fallen pods.
• September: Last month for pruning.
• November: Planting season begins; clear up pods.

What can you use it for?

Garden and landscape

Small flowering tree, also trained over an arch or pergola (laburnum tunnel).

Wood

Hard, dark heartwood for inlay work and turning.

For wildlife

Flowers for bumblebees and bees.

Caution: All parts, especially the seeds and pods, are highly poisonous. Do not plant it where young children play or next to pastures.

Did you know?

• Its dark, hard heartwood used to be called ‘false ebony’ and was used for inlay work and musical instruments.
• Like other members of the pea family, it fixes nitrogen from the air, with nodules on its roots.
• The hybrid ‘Vossii’ is a cross between common laburnum and Scotch laburnum.