Ornamental · Fabaceae
Lupine
Lupinus polyphyllus
Give it full sun, cool roots, and lean soil, and lupine throws up tall spires of color from late spring into summer.
Full sun
Every 3–7 days
USDA 4–8
3–4 ft · 0.9–1.2 m
Overview
Lupine sends up tall, dense spires of pea-like flowers above a fan of deeply divided leaves, and few border plants make a bolder early-summer show. It belongs to the legume family, so it pulls its own nitrogen from the air and asks little of the soil. The bigleaf type behind most garden strains hails from western North America and has naturalized widely in cool, temperate country.
Most of the named garden plants trace back to the Russell hybrids, a strain bred for fat, tightly packed spikes in clear colors and striking bicolors. They are perennials, though short-lived ones, and they shine brightest where summers stay cool. Give them a sunny spot with sharp drainage and they reward you fast.
There is a catch worth knowing from the start. Every part of the plant carries quinolizidine alkaloids, packed most heavily into the seeds and pods, which makes lupine a serious poison for grazing animals and no casual snack for people. It is grown to look at, not to eat.
Care
The short version: full sun with cool roots, planted in moderately rich, well-drained, slightly acidic soil kept evenly moist. Go light on feeding, deadhead the spent spikes, and plan to replace the plants every few years.
Light
Lupine wants full sun, and that's where the spikes come in tallest and most colorful. It will take partial shade, especially the afternoon kind in hot regions, but expect fewer, looser flowers in too much shade.
Water
Keep the soil evenly moist without letting it stay soggy, since these are plants of medium thirst, not bog dwellers. In warm regions a layer of mulch keeps the roots cool and the moisture steady. Sharp drainage matters as much as water here.
Soil
Plant in moderately rich, well-drained loam with plenty of organic matter worked in. Lupine leans toward the acidic side and is happiest at a pH of 5.5 to 6.5, so it sulks in chalky or heavy ground.
Temperature
This is a cold-hardy plant that shrugs off winters down to -29°F (-34°C) but resents real heat much past 84°F (29°C). Cool summers are what keep it vigorous, and hot, muggy ones shorten its life.
Humidity
Average outdoor humidity suits lupine fine, so there's no figure to chase. What counts is airflow, because still, damp air around crowded plants is what invites powdery mildew.
Feeding
As a nitrogen-fixing legume, lupine makes much of its own and needs very little feeding, a light low-nitrogen feed at the very most. Dust the roots with legume inoculant at planting and you'll get sturdier, better-performing plants.
Pruning
Deadhead the spent spikes as they fade to coax a second flush, keep the plant vigorous, and rein in self-seeding. Once flowering winds down, cut the tired foliage back to tidy the clump.
Size & spacing
Lupine stands 3 to 4 feet (91 to 122 cm) tall in bloom and forms a clump about 12 to 18 inches (30 to 46 cm) across. Give each plant that much elbow room so air moves freely and mildew stays away.
When to plant
Lupine runs on a cool-season rhythm. Sow seed in fall or start it indoors in late winter, set plants out in spring once the frost has passed, and the spikes open from May into July.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 6 to 8 weeks before last spring frost; nick/scarify and soak seed to aid germination
- Plant: Spring after last frost, or sow seed in fall
- Harvest: May to July
Hardiness
USDA hardiness zones: 4–8
Temperature: down to -34°C
Troubleshooting
Lupine stays mostly trouble-free, but a few familiar problems turn up on the leaves and new shoots. Catch them early and most are easy to set right. Match what you see below, then act before it spreads.
Dusty white film coating the leaves and stems
This is powdery mildew, a fungus that settles in when air sits still around crowded or shaded plants. Thin the clump and space things out so the leaves can dry, water at the base rather than from above, and strip off any badly coated foliage.
Fix:
- Improve air circulation by thinning and spacing plants
- Avoid overhead watering
- Remove and dispose of badly affected foliage
Sticky shoots crawling with tiny insects and curling tips
Those soft little bugs are aphids, and they crowd onto the tenderest new growth and flower spikes. Blast them off with a sharp jet of water, follow up with insecticidal soap if they hang on, and let lady beetles do the rest. Easy on the nitrogen, since the lush growth it pushes is exactly what they feed on.
Fix:
- Spray plants with a strong jet of water to dislodge aphids
- Apply insecticidal soap if needed
- Encourage natural predators such as lady beetles
A clump that fades and dies out after just a few years
Lupine is a short-lived perennial by nature, and hot, muggy summers cut its run even shorter. Most plants lose vigor and bloom within 2 to 5 years, so plan to replace them, grow them in cool-summer spots or treat them as annuals where it bakes, and let a few go to seed to keep the patch going.
Fix:
- Replace plants every few years
- Grow in cool-summer sites or treat as annual in hot zones
- Allow some self-seeding or start new plants from seed
Ragged holes chewed through young leaves overnight
Slugs and snails work after dark and go straight for soft seedlings, leaving silvery slime trails behind them. Hand-pick them at night or set out traps, clear away the damp debris and thick mulch they hide under near the crowns, and ring vulnerable plants with a barrier or iron-phosphate bait.
Fix:
- Hand-pick at night or set out traps
- Reduce damp hiding spots and mulch buildup near crowns
- Use barriers or iron-phosphate baits
Toxicity
Treat lupine as a poisonous plant. Every part holds quinolizidine alkaloids, concentrated in the seeds and pods, and grazing animals pay the steepest price. Pregnant cattle face the worst of it, since the teratogen anagyrine causes crooked calf disease, and no part of the plant is safe for people to eat off the stem.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Toxic
The quinolizidine alkaloids upset a cat's stomach and bring on vomiting and diarrhea. A bigger mouthful, especially of the seeds, can push into drooling, tremors, and other nervous signs, so keep the plant out of reach.
Dogs Toxic
A dog that chews lupine usually starts with vomiting and diarrhea. The seeds carry the most alkaloid, and a larger dose can leave a dog agitated, shaky, and unsteady on its feet.
Horses Severe
Horses are hit hard by the alkaloids, which cause muscle weakness, a wobbly stagger, and other nervous signs. The seeds and pods are the most dangerous parts and should never end up in their feed or pasture.
Rabbits Severe
Lupine is not safe forage for rabbits. The same quinolizidine alkaloids that poison larger grazers act on a rabbit's small body too, so keep the foliage, seeds, and pods well away from them.
Livestock Severe
Cattle, sheep, and goats suffer muscular weakness, ataxia, and nervous signs from the alkaloids. The real danger is to pregnant cattle that graze lupine on gestation days 40 to 100, where the teratogen anagyrine causes crooked calf disease, with skeletal contracture deformities and the occasional cleft palate.
Birds Severe
The alkaloid-rich seeds and pods are poisonous to birds, and the rest of the plant is no safer. Keep poultry and pet birds away from lupine entirely.
People Caution
No part of the garden lupine is casually edible. The bitter seeds are loaded with alkaloids and only become food after a long soaking and debittering process, so treat the whole plant as off the menu and keep children from sampling the seed pods.
Keep grazing animals, especially pregnant cattle, away from lupines; seeds and seed pods are the most alkaloid-rich parts.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Most garden lupines come from a few well-known strains and selections. These are the ones you'll meet most often.
Russell Hybrids
George Russell's classic strain carries tall, densely packed spikes in both bicolor and solid shades, but the seed you save from your own plants will not breed true.
The Governor
This bushy Russell-type selection stands out for its bold blue-and-white bicolor spikes.
Manhattan Lights
A compact hybrid that holds purple-and-yellow bicolor spikes on sturdy, upright stems.
How to propagate
Lupine is grown almost entirely from seed, though the hard coat needs a little help before it will sprout.
SeedModerate
Sow in fall, or start indoors 6 to 8 weeks before last spring frost · Blooms the first or second year from seed depending on sowing time
Lupine grows readily from seed if you give the hard coat a hand. Nick or scarify each seed and soak it before sowing, and dust the roots with legume inoculant to help young plants settle in. Sow in fall or start indoors 6 to 8 weeks before the last frost, and expect bloom the first or second year depending on when you sow. Keep in mind that hybrids will not come true from garden-saved seed.
Myths
Lupines are deadly to dogs and cats, so any contact is an emergency.
For a dog or cat, a nibble of lupine usually means nothing worse than vomiting or diarrhea. The grave danger falls on grazing livestock, above all pregnant cattle, where the alkaloids cause poisoning and the teratogen anagyrine triggers crooked calf disease.
You can save seed from Russell hybrid lupines and get identical plants.
Garden-saved seed from a hybrid scatters into a mix of unpredictable seedlings, not copies of the parent. Only purchased seed or vegetative propagation reliably reproduces a named strain.