Lupinus polyphyllus

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Bigleaf Lupine

Taxonomy

Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fabales
Family: Fabaceae
Genus: Lupinus
Species: Lupinus polyphyllus Lindl.
Garden forms: Russell hybrids, designated Lupinus × russellii hort. or L. × regalis

Common Names by Region

General / English: Bigleaf lupine, large-leaved lupine
United States / Canada: Bigleaf lupine, garden lupine, blue-pod lupine, marsh lupine
United Kingdom: Russell lupin, garden lupin
Northern Europe: Widely naturalized and generally treated as an invasive alien
Etymology: Lupinus is Latin for wolf — from an old and incorrect belief that these plants stripped the soil. They do the opposite; they fix nitrogen and leave ground richer. Polyphyllus means many-leaved, describing the high leaflet count.


Description

Growth Habit

An upright herbaceous perennial forming a basal clump of long-stalked leaves with flower stems rising above. Deep-rooted, which makes it useful for erosion control and difficult to move once established. Not woody at any point in its life — it dies back to the crown each winter.

Individual plants are relatively short-lived, three to five years typically, but a stand persists by seed.

Size

Height: 60–150 cm (2–5 ft) in flower; dwarf strains 45–60 cm
Spread: 45–75 cm (18–30 in)

Leaves
  • Palmately compound with 9 to 17 leaflets — the highest leaflet count in the common garden lupines and the source of the epithet
  • Leaflets broad, oblanceolate, glossy, and green, 4–15 cm long, mostly smooth above with fine hairs beneath
  • Long-petioled from the base, reducing upward on the flowering stem
  • The leaf holds water in beads after rain, which is one of the more photographed things about the plant
Stems
  • Erect, hollow, unbranched or lightly branched, ridged
  • Herbaceous throughout — no woody base. This is the fastest separation from tree lupine.
Flowers
  • Borne in dense terminal racemes 15–60 cm long, flowers whorled around the spike
  • Standard pea-flower structure: an upright banner petal, two wings, a fused keel enclosing the reproductive parts
  • Wild species color is blue to violet, occasionally pink or white
  • Bloom period late spring into midsummer — May through July in most of the range
Quick ID

Herbaceous clump, palmate leaves with 9 or more broad glossy leaflets, dense unbranched spike of pea flowers packed tight along its length. Separates from tree lupine (L. arboreus), which is a woody shrub with narrow silky gray-green leaflets, and from eastern wild lupine (L. perennis), which is smaller, with 7–11 narrower leaflets and a looser, more open spike.


The Russell Hybrids

Field note

Any yellow, red, orange, or bicolored garden lupine is not the wild species. Wild L. polyphyllus is blue.

George Russell, a gardener in York, began breeding lupines in his fifties after seeing a vase of them at an employer’s house. Over more than twenty years he crossed L. polyphyllus with tree lupine (L. arboreus) and one or more unrecorded annual species — possibly L. nootkatensis — relying on bumblebees for pollination and culling ruthlessly by eye. The yellows in the modern palette came in from arboreus.

He was 79 when he first exhibited at Chelsea. The Royal Horticultural Society awarded him the Veitch Memorial Medal in 1937. In 2013 the RHS named Russell Hybrid lupins the plant of their centenary decade and second overall across the century.

What he selected for is visible in any modern plant: spikes with the flowers packed tight and no gaps between whorls, where the wild species carries an open, gappy spike. If a lupine’s raceme looks like a solid column, that is Russell’s eye at work eighty years on.

Modern dwarf strains — Gallery, Minarette, Lulu — descend from this line, bred down for bedding and container use.

Note on this photograph: clear yellow flowers on a compact herbaceous plant with broad glossy leaflets and a tightly packed spike. That is a Russell-derived dwarf hybrid, most likely from one of the named bedding series, rather than the wild species.


Known Range

Native to western North America — British Columbia and Alberta south through Washington, Oregon, and California, east to Montana, Idaho, and Nevada. Habitat is streamsides, wet meadows, forest openings, and coastal ground. It prefers cool climates and moist soil.

Introduced and naturalized far beyond that, including eastern North America, across northern and central Europe, New Zealand, and elsewhere. In much of Europe, particularly Finland, Sweden, and the Baltic states, it is an established roadside and meadow invader listed as an invasive alien.

Hardy roughly USDA zones 4–8. Frost-tolerant to about −30 °F. Dislikes heat and humidity — it is a poor performer south of about zone 7.


Care / Habitat

  • Light: Full sun; part shade acceptable in warmer regions.
  • Soil: Moist, well-drained, slightly acidic. Alkaline ground causes chlorosis. Sandy or loamy over heavy clay.
  • Water: Even moisture. Mulch to keep roots cool.
  • Heat: The limiting factor. Cool summers produce good plants; hot humid ones produce mildew and collapse.
  • Feeding: Unnecessary. It fixes its own nitrogen, and rich soil shortens its life.
  • Placement: Mixed borders, cottage gardens, cutting beds, mass plantings.

Propagation / Reproduction

  • Direct sow. Lupines resent root disturbance badly, so sowing where they will grow is strongly preferable to transplanting.
  • Soak seed 24 hours in tepid water, or scarify, before sowing. The coat is hard.
  • Germination in roughly 20–25 days at 55–70 °F.
  • If starting indoors, use individual cells or peat pots, never open flats, and transplant before the taproot turns.
  • Basal cuttings in spring for named cultivars — the only way to hold a specific form, since seedlings of hybrids scatter across the color range.
  • Self-seeds readily where soil is open. Pods split explosively and throw seed several feet.
  • Pollination is by bumblebees, which are heavy enough to trip the keel. Russell relied on them entirely.

Pests / Diseases / Threats

  • Powdery mildew — the common one, worst in still humid conditions
  • Lupin aphid (Macrosiphum albifrons) — large gray aphids that colonize spikes and can kill plants
  • Slugs and snails on emerging spring growth, which they favor heavily
  • Anthracnose in wet seasons
  • Crown and root rot in heavy or poorly drained ground
  • Deer resistant

Toxicology

Field note

Do not eat any part of this plant. Lupinus polyphyllus contains quinolizidine alkaloids toxic to people and livestock. Seeds are the most concentrated part.

Some lupines are grown as food crops — L. albus, L. angustifolius, L. luteus — but those are low-alkaloid selected strains and still require processing before eating. Ornamental and wild lupines are not food.

Lupine is a recognized allergen with cross-reactivity to peanut, and a labeled allergen in the European Union.


The Lupinus perennis Problem

Field note

Anyone planting garden lupines in the eastern United States should know this.

Wild lupine, Lupinus perennis, is the eastern native — a smaller plant of sandy oak savanna and pine barrens, and the sole larval host plant of the Karner blue butterfly, a federally endangered species. Karner blue larvae eat L. perennis and nothing else.

L. polyphyllus and Russell hybrids do three things where they escape into eastern habitat: they spread aggressively in some conditions, they displace existing vegetation, and they hybridize with L. perennis. That last one is the serious one. Genetic swamping degrades the host plant the butterfly depends on, and hybrid plants are not reliable hosts.

The nitrogen fixation compounds it. Karner blue habitat is nutrient-poor sandy ground, and enriching that soil opens it to weeds that shade out the wild lupine directly.

None of this makes a bedding lupine in a suburban container an emergency. It does mean that seeding “lupine” into meadows, roadsides, or restoration plantings in the east is a real risk, and that “lupine” in a wildflower mix is almost always polyphyllus or a Russell hybrid rather than the native. If you want lupine in an eastern meadow, source L. perennis specifically and check with your state agriculture department or extension office first.


Additional Notes

  • Nitrogen fixation through root-nodule bacteria. The plant manufactures its own fertility and enriches the ground around it — an asset in a garden bed, a liability in any habitat whose native community depends on poor soil.
  • Pollinator value is high for bumblebees. Lupines are pollen flowers with no meaningful nectar, so they serve bees rather than butterflies or hummingbirds directly.
  • Erosion control is a genuine strength given the deep root system, and the reason the species has been deliberately sown along roadsides in several countries — which is also how much of the invasive range came to exist.
  • Deep taproot makes established plants near-impossible to move successfully. Site them once.
  • Cut flower use is common; harvest when the lowest third of the spike is open.
  • The New Zealand roadside lupine displays photographed constantly by tourists are naturalized Russell hybrids, not a native wildflower, and they are a management problem in braided river systems where they alter braid-plain habitat used by nesting birds.

Maintenance / Management

  • Deadhead spent spikes promptly for possible rebloom and to control self-seeding
  • Cut back to basal foliage after the main flush
  • Do not fertilize
  • Watch for aphids through the flowering period; a heavy infestation kills plants
  • Slug protection on emerging spring growth
  • Divide rarely, and expect losses — the taproot does not cooperate. Replace from seed instead.
  • Remove seed pods if the planting is anywhere near natural areas in the eastern United States

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