- Name also: Garden Lupin, Large-leaved Lupine, Largeleaf Lupin, Big-leaved Lupine, Bigleaf Lupin, Common Lupine, Blue-pod Lupine, Bog Lupine, Meadow Lupine, Russel Lupin (New Zealand)
- Family: Pea Family – Fabaceae (Leguminosae)
- Growing form: Perennial herb.
- Height: 60–100 cm (25–40 in.). Stem usually unbranched, sometimes branched when older, smoothly haired.
- Flower: Corolla zygomorphic, blue–purple or sometimes pink, white or multicoloured, 12–14 mm (0.48-0.55 in.) long. Petals five; the upstanding the ‘standard’, the lateral two the ‘wings’, the lower two united to form the ‘keel’, overall shape of corolla being butterfly-like. Calyx bilabiate, upper lip clearly shorter than lower. Stamens 10, filaments with fused bases. A single carpel. Inflorescence a long, dense raceme terminating stem.
- Leaves: Alternate, long-stalked, stipulate. Palmate leaves with 9–15 leaflets, tapered, with entire margins.
- Fruit: 2.5–4 cm (1–1.6 in.) long, sparsely hairy, brown, 5–9-seeded pod (legume).
- Habitat: Gardens, roadsides, railway embankments, wasteland. Also an ornamental.
- Flowering time: June–August.
- Harmfulness: Harmful invasive species.
Garden lupine is starting to become such an integral part of the summer along roadsides that it is rarely thought of any more as a foreign species. It is however originally native to the mountains of western North America, and it arrived in Finland as an ornamental in the 19th century. Many people would rather it had never arrived: garden lupine has spread along highway embankments and over fallow ground to the point that it already covers the whole country. As a large plant it leaves a number of our smaller natives in the shade, runs rings around other plants that often accompany it when it comes to enduring dry periods, and its root nodules fix nitrogen in the soil for its own requirements. Its excessive spread is already posing a threat to Finland’s smaller natives. When the naturally varied flower field has been turned into a sea of violet blue lupines, one begins to tire of the plant’s handsome conical inflorescence. Lupines often initially appear in a variety of colours, but over time the stands turn blue. This uniformity of colour is a genetic matter: the blue-colour genes are dominant.
Garden lupine has come to Finland to stay, but it might be possible to slow down its victory march. Individual plants can be dug out and large stands chopped down. Breaking off the inflorescence before the seed has ripened limits its spread to new areas. Lupine seeds remain viable for dozens of years, even centuries, so perseverance will be required to get rid of established stands. (Also in New Zealand this species, named there as Russel lupin, is classified as an invasive species.)
At first glance Nootka lupin which is quite rare in Finland, resembles garden lupin and also narrow-leaved lupine (L. angustifolius). There are differences: Nootka lupin’s palmate leaves have 6–8 leaflets (garden lupin has 10–16 which are more blunted. Corollas include more white (especially standards) and stem is branching (garden lupine branchless). Nootka lupin is classified (in Finland) as potentially or locally harmful alien species. Nootka lupin and garden lupin can cross-breed with each other.