Lupinus, commonly known as Lupine or Lupin, is a genus of flowering plants in the Legume family, Fabaceae. They are attractive and spiky, reaching 1 to 4 feet (30 cm to 1.2 m) in height and adding color and texture to the back of a flower bed. Lupine flowers may be annual and last only for a season or perennial, returning for a few years in the same spot in which they were planted. Lupine grows from a long taproot and does not like to be moved.
If the growing conditions are right, Lupine flowers are equally at home in the garden or on the side of the road. Lupines bloom over a two-month period, which can range from May to July, depending on the variety and the growing zone.
Lupines need neutral to slightly acidic soil, although they can grow in very acidic soil conditions. Lupines don't need rich loam, but it's important to grow the plants in very well-draining soil to avoid root rot. Sandy soil conditions and poor rocky soil promote the growth of the Lupine's deep tap root.
Starting Lupines from seed is an economical way to get a showy flower garden the following season.
The seed coat is tough, and seeds have a better germination rate if you nick the seed coat or soak them in water overnight. Plant them about 0.25 inch (6 mm) deep outdoors in a permanent area that receives full sun, as they do not transplant well due to their long tap root. Expect germination in 14 to 30 days.
Although Lupines demand good drainage, they also like regular irrigation, so provide the equivalent of 1 inch (2.5 cm) of rain each week if conditions are dry.
Lupines don't require fertilization, and in fact, too much fertilizer can encourage excess foliage growth at the expense of blooms.
The tall Lupine hybrids may benefit from staking. You can use grow-through grid stakes to avoid the labor of fastening individual stalks to stakes.
Lupines benefit from deadheading, or removing spent blooms after flowering. This prevents unwanted volunteers from taking over the garden, and may encourage some additional reblooming. By preventing Lupines from developing seed heads, you also allow the plant to redirect energy into root and foliage growth, which results in increased plant vigor.
Pests and Problems
Lupines are subject to a few pests and diseases. Aphids are common in early spring, as are slugs and snails. Powdery mildew can colonize plants in the rainy season, to the point where it's best just to cut damaged foliage away and wait for regrowth.