Wildflower watchers everywhere celebrate when springtime lupines come into bloom. The types grown in gardens are generally hybrid crosses (Lupinus × hybrida) of various native species, bred to maximize flower color and vigor. Lupinus is an enormous genus of flowering plants, comprising hundreds of species. The colorful hybrid lupines most popular for gardens were primarily derived from Lupinus polyphyllus, a North American native, crossed with various other species, such as Lupinus arboreus.
There is nothing subtle about hybrid lupines. The telltale look is a tall, showy spire of flowers that can come in a multitude of colors. The foliage resembles palm leaves with seven to 10 leaflet segments each. This fast-growing flower is available as both an annual and a perennial. Potted lupines most often are perennial varieties. They're best planted in spring when starting with a new plant or cuttings. Seeds can be planted in late spring or fall. Perennial plants grown from seed likely won't bloom until their second year.
|Botanical Name||Lupinus x hybrida|
|Common Names||Lupine, bluebonnet|
|Plant Type||Herbaceous, perennial, annual|
|Mature Size||3–4 ft. tall, 1–1.5 ft. wide|
|Soil Type||Rich, moist, well-drained|
|Soil pH||Acidic, neutral|
|Bloom Time||Spring, summer|
|Flower Color||White, pink, red, yellow, blue, purple, bicolor|
|Hardiness Zones||4–8 (USDA)|
|Native Area||Parent species mostly native to North America|
|Toxicity||Toxic to humans and animals|
People once believed that lupine flowers soaked up all of the nutrients from the soil, leading to their common name being derived from the Latin word for wolf. However, Lupinus plants are members of the pea family, Fabaceae, and like peas the plants actually are capable of fixing nitrogen in the soil. They make for wonderful garden border plants, though some of the taller varieties might need staking to prevent them from flopping over. You can use grow-through grid stakes to avoid having to tie individual stems to stakes.
Although rainbow hybrid lupine seed mixes are the most popular commercially available lupine, the original blue strain is the hardiest. When grown in their preferred conditions, lupines require very little care. Be sure to deadhead your plants (remove spent flowers) to encourage additional blooming. And water them during periods of dry weather.
Lupines prefer full sun, at least six hours of direct sunlight on most days, to grow and bloom their best. They can grow in partial shade, but their flowering will be diminished. However, some afternoon shade is ideal in hot climates. If you plant lupines in deep shade, they typically won't flower. A remedy for shady conditions is to trim back neighboring shrubs and trees to allow some sun to hit the lupines.
These flowers like organically rich soil with sharp drainage. They prefer a neutral to slightly acidic soil pH, though they also can grow in very acidic soil conditions.
While lupines don't like soggy soil, which can cause root rot, they prefer regular waterings. Water at least weekly if you haven't gotten rainfall to prevent the soil from drying out.
Temperature and Humidity
Lupines like climates with fairly cool summers. They don't do well in hot, humid climates, such as that of the Southern U.S. High heat and strong sunlight can result in the plants failing to flower. In hot climates, a light layer of mulch around the lupines can help to retain soil moisture and keep the roots cool.
Lupines generally don't require fertilizer, and in fact too much fertilizer can encourage excess foliage growth at the expense of blooms. However, an acidifying fertilizer can be useful for lowering the soil pH of alkaline soils.
Are Lupines Toxic?
Many, but not all, plants in the Lupinus genus are toxic to humans and animals. The seeds and seed pods are the most toxic parts, and seeds typically must be eaten in large quantities to cause symptoms. However, livestock such as sheep, goats, and cattle are highly prone to lupine poisoning from grazing on mature plants, particularly the seed pods.
Symptoms of Poisoning
Common symptoms of poisoning in humans and animals include fatigue, a slow heart rate, slowed breathing, and convulsions. If you suspect poisoning, contact a medical professional as soon as possible.
There are several lupine varieties available that vary in appearance, including:
- Russell mixed colors: Bred in 1937 and naturalized in many areas, this hybrid rainbow and bicolor mixture is the foundation for all new cultivars.
- Gallery series: Dense flower spikes on this compact plant grow no more than 2 feet tall.
- 'Dwarf Lulu': These plants grow about 2 feet tall in a rainbow of hues and feature unusually dense racemes.
- 'Minarette': This 18-inch variety looks stunning in drifts along a border's edge or in containers.
Because lupines sprout so easily from seed, this is the normal method for growing them. But lupines can also be propagated by carefully taking basal cuttings from established plants in the spring. Use a sharp knife to sever a segment of crown and roots from the parent plant, and transplant it to a new location. It's important to do this in early spring before the plant has begun to actively grow and leaf out. It's a good idea to propagate your lupines every two to three years, as they are short-lived plants. Basal propagation ensures that you'll have an ongoing stock of your favorite plants.
How to Grow Lupines From Seed
Starting lupines from seed is an economical way to get a showy flower garden the following season. They are among the easiest perennials to grow from seeds. The seed coat is tough, so seeds have a better germination rate if you nick the seed coat or soak it in water overnight. Plant the seeds about 1/4 inch deep outdoors in a permanent area that receives full sun; lupines do not transplant easily due to their long taproots. Expect germination in 14 to 30 days.
Lupines are vulnerable to several pests and diseases. Aphids are common in spring, as are slugs and snails. Control pests with horticultural oils or pesticides, as they can carry more serious diseases to the plants.
Lupines are also susceptible to brown spot fungus, where various parts of the plants will develop brown patches. Remove and destroy affected plants, and avoid using the area to grow lupines for several years so the spores have time to die off. Furthermore, powdery mildew can impact lupines, especially if there isn't good air circulation around the plants. This fungal disease shows up as white, powdery patches on the foliage, and there are multiple chemical and organic methods to control it. You also can simply cut away the foliage and wait for regrowth.
The Perils of Over-Fertilizing Plants and Trees. University of California Agriculture and Natural Resources.
Al-Abdouh, Ahmad, Alrawashdeh, Hamzeh Mohammad, Khalaf, Ahmad, Alnawaiseh, Ibrahim. Anticholingergic Toxicity Associated with Lupine Seeds Ingestion - A Case Report. Research in Health Science, 5,1,2020, doi:10.22158/rhs.v5n1p22
Aphids on Shade Trees and Ornamentals. Colorado State University Extension.
Diagnosing Brown Spot in Narrow-Leafed Lupins. Government of Western Australia Department of Primary Industries and Regional Development.
Lupine (Lupinus spp.) -Powdery Mildew. Pacific Northwest Pest Management Handbook.