Garden lupin

How to recognise it

Habit

Perennial forming a sturdy clump 80–150 cm tall and 50–60 cm wide. Dies back above ground in winter.

Leaves

Palmate, with 9–17 narrow, lance-shaped leaflets on a long stalk; slightly hairy underneath.

Flowers

Pea flowers in dense, upright spikes of 30–50 cm, from June to August. Blue-violet in the wild, in gardens also pink, white, yellow, red and bicoloured.

Fruit

Hairy pods of 3–5 cm that split open when ripe and fling the seeds several metres away.

Roots

A deep taproot with nodules in which bacteria fix nitrogen; this is why it dislikes being moved.

Confusion with

Tree lupin is a small shrub, usually with yellow flowers. Annual lupins from farm and green-manure mixes stay lower and have fewer leaflets.

Flowering: June–August · Pruning: July and October

Why grow it?

• Bumblebees and bees gather plenty of pollen: the flowers are mainly a pollen source, with little nectar.
• One of the most striking flowers of early summer, with spikes up to 50 cm long.
• Often flowers again in August if you cut off the spent spikes in time.
• Fixes nitrogen from the air through its root nodules, so it grows even on poor, sandy soil.
• The hand-shaped leaves are attractive even out of flower: after rain a drop of water sits like a pearl in the centre.

Garden lupin: where does it grow best?

• In the wild: road verges, railway banks, sandy waste ground, rough grassland and woodland clearings, mainly on sand.
• In the garden: full sun or light shade.
• Light, free-draining, preferably slightly acid soil; on heavy, wet clay or chalky soil it does not last long.
• Grow it in a sunny border, not in a poor, flower-rich meadow: there it enriches the soil and crowds out other species.

Goes well with

• Catmint: Low blue cushions at the base, also loved by bees.
• Delphinium: More tall spires in the summer border.
• Oxeye daisy: White flowers among the colourful spikes.
• Oriental poppy: Flowers at the same time, in a warm contrast.
• Ornamental grasses: Fill the space when the lupin looks tired in late summer.

Garden lupin: when and how to plant it?

1. Buy young potted plants from a nursery and plant them in April–May or September–October.
2. Or sow: soak the hard seed overnight in lukewarm water or rub it lightly with sandpaper, then sow 1–2 cm deep in April–May, in deep pots or where it is to grow.
3. Plant 50–60 cm apart, at the same depth as in the pot, without damaging the taproot.
4. Water after planting and keep the soil moist for the first few weeks, then only in dry spells.
5. Protect the young shoots from slugs in spring.
6. Do not sow or plant it in or near nature reserves and poor grasslands, and never dig up plants from the wild.

Care

Water

Little needed once established, thanks to the deep taproot; only in long droughts.

Feeding

Not needed: it makes its own nitrogen. Fertiliser mainly gives lots of leaves and floppy stems.

Spent spikes

Cut them off before they set seed: this often gives a second flush and prevents unwanted seedlings.

Support

In a windy spot, add a plant support or a few canes, as the heavy spikes snap in storms.

Lifespan

Garden lupins are fairly short-lived: after a few years they flower less. Keep them young by taking cuttings in time.

Tip: Cut the flower spikes straight after the first flush: you will often get a second flush in August, and no poisonous pods or unwanted seedlings.

Pruning and mowing

Pruning months: July and October.

When: In July cut off spent spikes; in October–November cut back the dead stems.

How:

• Cut spent spikes back to just above a strong leaf, before the pods ripen.
• To collect seed, leave one spike and cut it as soon as the pods turn brown, before they burst open.
• In autumn cut the yellowed leaves and stems back to 5–10 cm above the ground.
• Feel free to leave a few hollow stems until spring for overwintering insects.

Caution: Keep ripe pods out of reach of children: the seeds look like peas but are poisonous.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Basal cuttings

In March–April cut young shoots of 8–10 cm with a small piece of rootstock at the base and set them in sandy cutting compost. This gives exactly the same colour.

Seed

Soak or rub the seed and sow in April–May. Seedlings of garden varieties often give different colours from the parent plant.

Self-seeding

It self-seeds; weed out unwanted seedlings while they are small.

Garden lupin: how does it get through the winter?

Hardy to −25 °C.

• It dies back completely above ground; the rootstock overwinters deep in the soil and is fully hardy.
• In early spring the first rosettes of small hand-shaped leaves appear, much loved by slugs.
• On wet, heavy soil the root can rot in winter, so choose a free-draining spot.

Diseases and pests

• Lupin aphid: Large greyish-white aphids that cover the flower spikes in May–June. Hose them off with a strong jet of water, let ladybirds do their work and cut off badly affected spikes.
• Slugs: They strip the young shoots in March–April. Pick them off in the evening or put a collar around the young plant.
• Powdery mildew: White powder on the leaves in late summer, especially in dry weather. Cut the foliage back after flowering for fresh new leaves.
• Root rot: On wet, heavy soil the root rots and the plant dies. Choose light, free-draining soil.
• Escaping: It self-seeds and can crowd out other plants on poor verges and grasslands. Cut off spent spikes in time.

Through the year

• March: Young shoots. Watch out for slugs. Take basal cuttings.
• April: Plant or sow. Put supports in place in windy spots.
• May: The flower spikes grow. Watch for aphids.
• June: Full flower. Bumblebees on the flowers.
• July: Cut off spent spikes for a second flush.
• August: Second, smaller flush. Water in long droughts.
• September: Planting is possible. Remove ripe pods in time.
• October: Cut dead stems back to 5–10 cm.
• November: Resting underground.

Did you know?

• The well-known Russell lupins are named after George Russell, a gardener from York who selected them for years; they came on the market in the 1930s.
• Polyphyllus means ‘many-leaved’, after the many leaflets of each leaf.
• In Scandinavia and parts of central Europe it has spread so widely along verges and in grasslands that it is regarded as a problem species there.