Bigleaf lupine (Lupinus polyphyllus)

Common Names: Garden lupine, large-leaved lupine, giant lupine, Russell lupine

Description:

Bigleaf lupine (Lupinus polyphyllus) is a tall, showy perennial wildflower in the pea family, native to western North America [1][4]. It was spread far beyond that range as a popular garden plant, and it now grows wild across the eastern U.S., the Great Lakes region, and Europe [1][2]. MISIN tracks it because it is not native here and spreads aggressively into meadows and roadsides, where it crowds out native plants and can harm the native wild lupine that the endangered Karner blue butterfly depends on [2][3].

Habit:

Bigleaf lupine is a clump-forming perennial that stands 2 to 4 feet tall, sometimes reaching 5 feet [1][2]. Its leaves are its signature: each one is round in outline and divided like the spokes of a wheel into 11 to 18 narrow leaflets, hairy underneath, on a long stalk [1][2]. In early to midsummer it sends up tall spikes packed with pea-like flowers, usually blue-violet but also pink, purple, or white in garden-derived plants [1][2]. The flowers open from the bottom of the spike upward [1]. It is easiest to spot in late spring and early summer, when the colorful flower spikes line roadsides and ditches and stand well above surrounding plants [1].

At-a-glance cues:

1. Round, wheel-spoke leaves divided into 11 to 18 narrow leaflets [1][2]
2. Tall spikes (6 to 18 inches) of pea-like flowers, often blue-violet but sometimes pink, purple, or white [1][2]
3. Stands 2 to 4 feet tall, sometimes up to 5 feet ? taller than the native wild lupine [1][2]
4. Flowers bloom in early to midsummer and open from the bottom of the spike upward [1]

Leaves:

1. Arranged alternately along the stem, on long stalks (petioles) [1]
2. Palmately compound ? leaflets spread from a central point like the spokes of a wheel [1]
3. 11 to 18 narrow leaflets per leaf [1][2]
4. Hairy on the underside [1]

Stems:

1. Herbaceous (not woody); dies back to the ground each winter and regrows from a thick root each spring [1]
2. Upright, growing in clumps 2 to 4 feet tall, sometimes up to 5 feet [1][2]
3. Grows from a stout taproot [1]

Flowers:

1. Pea-like (typical of the bean family), about 1/2 inch long [1]
2. Usually blue-violet; garden-derived plants also come in pink, purple, red, or white [1][2]
3. Crowded onto tall, dense spikes (racemes) 6 to 18 inches long at the top of the stem [1][2]
4. Bloom in early to midsummer; flowers open from the bottom of the spike upward; each flower is perfect (has both male and female parts) [1]

Fruit and seeds:

1. Fruit is an oblong, flattened, hairy pod, like a small hairy pea pod [1]
2. Each pod holds 3 to 9 seeds [1]
3. Pods dry and split open, flinging seeds a short distance from the parent plant [1]
4. The plant produces seed in large numbers, building a long-lasting seed bank in the soil [1][3]

Habitat:

Bigleaf lupine grows best in open, sunny places with moist soil ? roadsides, ditches, railway banks, stream edges, meadows, old fields, and prairies [1][3]. As a member of the pea family, it hosts bacteria on its roots that pull nitrogen from the air and feed it into the soil, so it can thrive on poor, gravelly ground where many native plants struggle [3]. It is native to the western United States and Canada ? not to the Great Lakes region or the eastern U.S. [1][4]. In those areas, and across Europe, it has escaped from gardens and become a widespread invader of grasslands and road verges [2][3].

Reproduction:

Bigleaf lupine spreads almost entirely by seed, and it makes a lot of it [1][3]. The dry pods split open and fling seeds a short distance, and from there seeds are moved farther in soil, on mowing and roadwork equipment, in dumped garden waste, and along road and rail corridors [1]. Many seeds stay alive in the soil for years, so a patch can keep coming back long after the visible plants are gone [3]. A planted lupine in a yard can also seed itself into nearby natural areas.

The plant is a perennial: it dies back each winter and regrows from its thick root each spring, getting larger and seeding more heavily over time [1]. Seeds sprout in spring, and plants flower and set seed in their second year or later [1]. For control, the key is timing ? cut or pull plants before the pods ripen in mid to late summer, so they cannot drop a new crop of seed [1].

Impact and Damage:

Bigleaf lupine is grown in gardens for its tall, colorful flower spikes, and it does provide pollen for bees [2]. The problem is what it does when it escapes [2][3]. It forms dense stands that crowd out native wildflowers and grasses, and studies in invaded grasslands found fewer plant species growing where lupine had taken hold [3]. Because its roots add nitrogen to the soil, it changes the ground itself, enriching poor soils in a way that favors other weeds and pushes out the native plants adapted to low-nutrient meadows and prairies [3]. The most serious concern in the Great Lakes region is its effect on the native wild lupine (Lupinus perennis), the only food plant of the caterpillars of the endangered Karner blue butterfly [2]. Bigleaf lupine looks similar and cross-breeds with wild lupine, and the resulting hybrid plants cannot support Karner blue caterpillars ? so its spread can quietly degrade the butterfly's habitat even where lupine still appears to be present [2].

Similar species:

Bigleaf lupine is easily mixed up with other lupines. Telling them apart matters because one look-alike is a protected native.

Wild lupine (Lupinus perennis), also called sundial lupine, is the native species and the most important to distinguish ? it is the only food plant of the endangered Karner blue butterfly's caterpillars. It is shorter, usually around 2 feet, with fewer leaflets (7 to 11) and looser flower spikes that are blue-violet only. It grows in dry, sandy soils, while bigleaf lupine is taller, has 11 to 18 leaflets and denser, often multicolored spikes, and prefers moister ground [2].

Russell lupine (Lupinus ? regalis) is a group of garden hybrids bred largely from bigleaf lupine, sold in a wide range of flower colors. It looks almost identical to bigleaf lupine and can escape gardens and cross with wild lupine in the same way, so escaped plants are best treated the same [2].

Monitoring and rapid response:

Signs to watch for:

1. Tall, dense spikes of pea-like flowers ? often blue-violet, sometimes pink, purple, or white ? standing above other plants in early to midsummer [1][2]
2. Round, wheel-spoke leaves with 11 to 18 narrow leaflets [1][2]
3. Clumps along roadsides, ditches, stream banks, and meadows, especially on moist ground [1]
4. Plants taller than knee height, taller and bushier than the native wild lupine [2]

What you can do:

1. Dig out individual plants, removing as much of the thick root as possible; cutting the root a couple of inches below the soil line with a sharp spade also works [1]
2. Cut or mow plants before the pods ripen in mid to late summer to stop seed from forming and spreading [1]
3. Bag and dispose of flower and seed spikes rather than composting them or leaving them on site, since seeds can still ripen after cutting [1]
4. Do not plant bigleaf lupine or Russell hybrid lupines, and remove any in your yard near natural areas; choose the native wild lupine instead where appropriate [2]
5. Watch the spot for several seasons and remove new seedlings as they appear, because seeds survive a long time in the soil [1][3]
6. Natural area crews can clear larger stands by repeated mowing and digging before seed set, tackle small outlying patches first, and take special care to protect native wild lupine and Karner blue butterfly habitat [1][2]

When to call a professional:

1. Large, well-established stands that keep coming back from the root and the seed bank [1][3]
2. Infestations in or near sensitive sites such as wild-lupine meadows that support the Karner blue butterfly [2]
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Wisconsin Department of Natural Resources. Big-leaf lupine (Lupinus polyphyllus). dnr.wisconsin.gov
2. University of New Hampshire Extension (2024). What are the differences between the native wild lupine and bigleaf lupine commonly seen in New Hampshire landscapes? extension.unh.edu
3. Prass M, Ramula S, Jauni M, Setala H, Kotze DJ (2021). "The invasive herb Lupinus polyphyllus can reduce plant species richness independently of local invasion age." Biological Invasions 23:2901?2914. doi.org/10.1007/s10530-021-02652-y
4. USDA NRCS PLANTS Database. Lupinus polyphyllus Lindl. (LUPO2). plants.usda.gov

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