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 shoots up tall, crowded spires of pea-like flowers over a fan of deeply split leaves, and not much else in the border can match that early-summer show. It's a member of the legume family, so it grabs its own nitrogen straight from the air and doesn't ask much of your soil. The bigleaf type behind most of the garden strains comes from western North America, and it's settled in across cool, temperate places.
Nearly all the named garden plants go back to the Russell hybrids, a strain bred for those full, tightly packed spikes in clear colors and eye-catching bicolors. They're perennials, sure, but short-lived ones, and they do their best where summers stay cool. Want fast results? Give them a sunny spot with sharp drainage and they'll deliver.
There's one catch you'll want to know about up front. Every part of the plant carries quinolizidine alkaloids, packed heaviest into the seeds and pods, and that makes lupine a real poison for grazing animals and nothing for people to snack on either. It's here to be looked at, not eaten.
Care
The short version: give lupine full sun with cool roots, put it in moderately rich, well-drained, slightly acidic soil, and keep that soil evenly moist. Go easy on the feeding, snip off the spent spikes, and plan on fresh plants every few years.
Light
Lupine really wants full sun, and that's where you'll get the tallest, most colorful spikes. It'll put up with partial shade, the afternoon kind especially if you're somewhere hot, but too much shade and you'll end up with fewer, floppier flowers.
Water
Keep the soil evenly moist but not soggy, because lupine's a medium-thirst plant, not a bog lover. Somewhere warm? A layer of mulch keeps the roots cool and the moisture steady. And honestly, good drainage matters just as much as the watering does.
Soil
Get it into moderately rich, well-drained loam with plenty of organic matter mixed in. Lupine likes things a touch acidic and is happiest at a pH of 5.5 to 6.5, so it tends to sulk in chalky or heavy ground.
Temperature
This one's tough in the cold, shrugging off winters down to -29°F (-34°C), but it's not a fan of real heat much past 84°F (29°C). Cool summers keep it going strong, while hot, muggy ones cut its life short.
Humidity
Average outdoor humidity is fine for lupine, so there's no number you need to hit. What actually matters is airflow, since still, damp air around crowded plants is exactly what brings on powdery mildew.
Feeding
Being a nitrogen-fixing legume, lupine makes plenty of its own and barely needs feeding, just a light low-nitrogen feed at the very most. Dust the roots with legume inoculant at planting and you'll get sturdier plants that grow better.
Pruning
Deadhead the spent spikes as they fade and you'll coax a second flush, keep the plant vigorous, and keep self-seeding in check. Once the flowering's winding down, cut the tired old foliage back to tidy things up.
Size & spacing
Lupine hits 3 to 4 feet (91 to 122 cm) tall when it's blooming and makes a clump about 12 to 18 inches (30 to 46 cm) wide. Give each one that much room so the air moves through and mildew stays away.
When to plant
Lupine runs on a cool-season schedule, which is easy enough to work with. Sow seed in fall or start it indoors in late winter, pop the plants outside in spring once frost's done, and the spikes open up 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's mostly an easy plant, but a few of the usual suspects can turn up on the leaves and new shoots. Spot them early and most are no big deal to fix. Find what matches what you're seeing below, then get on it before it spreads.
That chalky white film showing up on leaves and stems
What you're looking at is powdery mildew, a fungus that loves stale air around plants that are packed too close or sitting in shade. The fix is pretty simple: thin the clump so the leaves can breathe and dry out, water down at the base instead of over the top, and pull off whatever's badly coated.
Fix:
- Improve air circulation by thinning and spacing plants
- Avoid overhead watering
- Remove and dispose of badly affected foliage
Little bugs bunched on new growth with the tips going wonky
Those tiny clusters on the soft new shoots and flower spikes? They're aphids, and they always pick the tenderest bits. Knock them off with a strong spray of water first, and if a few stubborn ones stick around, insecticidal soap sorts them out. Lady beetles will happily eat the rest, and going easy on nitrogen helps too, since all that soft growth is basically an aphid buffet.
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 healthy clump that just peters out after a few years
Here's the thing, lupine is a short-lived perennial to begin with, and hot, sticky summers make that even shorter. Most plants start losing their oomph and their flowers within 2 to 5 years, so it pays to keep some replacements coming. Grow them somewhere with cool summers, or just treat them as annuals if your place bakes, and let a few go to seed so the patch keeps itself 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
Holes chewed through young leaves seemingly overnight
See ragged holes with shiny trails nearby? That's the work of slugs and snails, which come out after dark and go for the softest seedlings. Head out at night with a torch and pick them off, or set some traps, and clear away the damp debris and thick mulch they hide in near the crowns. A barrier or some iron-phosphate bait around the plants finishes the job.
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
It's best to treat lupine as a poisonous plant from the get-go. Every part carries quinolizidine alkaloids, packed into the seeds and pods, and grazing animals get the worst of it. Pregnant cattle really take the hit, 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
If a cat takes a bite, the quinolizidine alkaloids tend to upset its stomach, so you'll usually see vomiting and diarrhea. A bigger mouthful, and the seeds especially, can bring on drooling and tremors, so it's smart to keep the plant somewhere the cat can't get to.
Dogs Toxic
A dog that chews on lupine will usually get vomiting and diarrhea to start. Since the seeds hold the most alkaloid, a larger helping can leave a dog jittery, shaky, and a bit wobbly on its feet.
Horses Severe
Horses really don't handle these alkaloids well, and they can end up with muscle weakness, a staggering walk, and other nervous signs. The seeds and pods are the worst of it, so you'll want to make sure none of that gets into their feed or pasture.
Rabbits Severe
Lupine isn't safe forage for rabbits, plain and simple. Those same quinolizidine alkaloids that hurt bigger grazers work on a rabbit's little body too, so keep the leaves, seeds, and pods well out of their way.
Livestock Severe
Cattle, sheep, and goats can wind up with muscle weakness, ataxia, and nervous signs from the alkaloids. The scariest part is pregnant cattle grazing lupine on gestation days 40 to 100, because that's when the teratogen anagyrine causes crooked calf disease, with skeletal contracture deformities and sometimes a cleft palate.
Birds Severe
The alkaloid-rich seeds and pods are poisonous to birds, and honestly the rest of the plant isn't any better. Just keep poultry and pet birds away from lupine completely.
People Caution
No part of garden lupine is something you'd casually eat. The bitter seeds are packed with alkaloids and only turn edible after a long soak-and-debitter routine, so treat the whole plant as off-limits and keep kids from nibbling the 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 trace back to just a few well-known strains and selections. Here are the ones you'll bump into most.
Russell Hybrids
George Russell's famous strain gives you tall, tightly packed spikes in both bicolors and solid colors, though don't count on the seed you save at home to come back true.
The Governor
This bushy Russell-type pick is easy to spot thanks to its bold blue-and-white bicolor spikes.
Manhattan Lights
This compact hybrid carries purple-and-yellow bicolor spikes on stems that stay nice and upright.
How to propagate
Lupine is grown almost entirely from seed, though that hard coat needs a bit of help before it'll 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's easy from seed, as long as you help that tough coat along first. Nick or scarify each seed, give it a soak before you sow, and dust the roots with legume inoculant so the young plants settle in nicely. Sow in fall or start indoors 6 to 8 weeks before the last frost, and you'll get bloom the first or second year depending on when you sowed. One heads-up though, hybrids won't come true from seed you save yourself.
Myths
Lupines are deadly to dogs and cats, so any contact is an emergency.
For a dog or cat, a little nibble of lupine usually just means some vomiting or diarrhea, so no need to panic. The real trouble is with grazing livestock, especially pregnant cattle, where the alkaloids cause actual poisoning and the teratogen anagyrine sets off crooked calf disease.
You can save seed from Russell hybrid lupines and get identical plants.
Save seed from a hybrid and what you'll get is a grab-bag of unpredictable seedlings, not copies of the parent. If you want a named strain to come back reliably, buy fresh seed or propagate it vegetatively.