Wildflower watchers everywhere celebrate when springtime lupines come into bloom, heralding the flowers' appearance with tours and festivals from Maine to California. The types grown in gardens, however, are generally hybrid crosses of various native species, bred to maximize flower color and vigor. One example is the Russell Hybrids, which produce stately spires of flowers in a multitude of vibrant colors.
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 dense floral spikes of lupines may grace your flower garden in bold shades of purple, pink, red, white, and yellow. The foliage resembles palm leaves, with seven to 10 leaflet segments each.
Lupinus is an enormous genus of flowering plants, comprising hundreds of species. The colorful hybrid lupines most popular for gardens were mostly derived from Lupinus polyphyllus, a North American native, crossed with various other species, such as L. arboreus, and then developed into various multi-colored cultivars. Today, some of the so-called "wild" lupines are not the original natives, but rather garden varieties that have escaped, reverted to alien parent species, and naturalized as invaders.
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 in fall. They have very tough seed coats, so either soak the seeds in water for 24 hours or scarify the seed coating with sandpaper. Perennial plants grown from seed likely will not bloom until their second year.
|Botanical Name||Lupinus x hybrida|
|Common Names||Lupine, bluebonnet|
|Plant Type||Herbaceous perennial|
|Mature Size||1 to 5 feet tall|
|Sun Exposure||Full sun to part shade|
|Soil pH||Below 6.5 (Acidic to neutral)|
|Bloom Time||Spring, summer|
|Flower Color||White, red, pink, yellow, blue, purple, bicolored|
|Hardiness Zones||3 to 7|
|Native Area||Parent species of most hybrids are native to North America|
|Toxicity||Toxic to humans and pets|
Lupines prefer to grow in rich, slightly acidic soil in a full-sun location. In a suitable location, they require very little care, other than removing spent flowers to encourage additional blooming. But these plants do not like hot, humid weather and can languish during the mid-summer months. The tall Russell lupine hybrids may benefit from staking. You can use grow-through grid stakes to avoid having to tie individual stalks to stakes. These are short-lived perennials, so do not expect them to live more than a few years.
People once believed that lupine flowers soaked up all of the nutrients from the soil, leading to its common name, derived from the Latin word for wolf. However, Lupinus plants are members of the pea family, Fabaceae, and like peas, the plants are capable of fixing nitrogen in the soil.
Full sun is preferred. Lupine can grow in part shade, but flowering will be lessened. If you plant lupines in deep shade, they will not flower. The remedy is to trim back neighboring shrubs and trees.
Lupines need neutral to slightly acidic soil, although they can grow in very acidic soil conditions. Lupines do not need rich loam, but it is 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 taproot.
Although lupines demand good drainage, they also like regular irrigation, so provide the equivalent of 1 inch of rain each week if conditions are dry. Lightly mulch lupines in hot climates to keep the soil cool and moist.
Temperature and Humidity
Lupines might fail to flower if there is too much sun or high temperatures, especially in early summer. Lupines prefer cool sunshine to sweltering summer sun.
Lupines do not 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.
Is Lupine 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 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 seed pods. Common symptoms of poisoning in humans and pets include sleepiness, slowed pulse, respiratory depression, and convulsions.
Varieties of Lupines
Although rainbow hybrid lupine seed mixes are the most popular commercially available lupine, the original blue strain is the hardiest. Over time, the blue lupines in a rainbow mix will persist and become perennials, while the less adaptable colors die out.
- Russell mixed colors: Bred in 1937 and naturalized in many areas, this hybrid rainbow and bicolor mixture is the foundation for all new cultivars.
- Lupinus polyphyllus: The species of native lupine sold in wildflower mixtures consists of all blue flowers.
- 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 the border's edge or in flowering containers.
Because lupines grow so easily from seeds, this is the normal method for growing them. Lupines will readily self-seed in the garden, but the volunteers of hybrid plants do not come true from hybrid plants.
Lupines can also be propagated by carefully taking basal cuttings from established plants in early spring. Use a sharp knife to sever a segment of crown and roots from the parent plant, and transplant it into a new location. It's important to do this in spring, before the plant has begun to actively grow and leaf out. It's a good idea to do this every two or three years, as lupines are short-lived plants. Basal propagation ensures that you'll have an ongoing stock of favorite plants.
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.
How to Grow Lupine From Seeds
Starting lupines from seed is an economical way to get a showy flower garden the following season. They are among the easier perennials to grow from seeds.
The seed coat is tough, and seeds have a better germination rate if you nick the seed coat or soak it in water overnight. Plant lupines about 1/4 inch deep outdoors in a permanent area that receives full sun; they do not transplant easily due to their long taproots. Expect germination in 14 to 30 days. Plants started from seeds may not bloom until their second year.
Common Pests and Diseases
Lupines are subject to a fairly large number of pests and diseases. Aphids are common in early spring, as are slugs and snails. Aphids should be controlled with horticultural oils or pesticides, as they can be the vector for more serious diseases, such as cucumber mosaic virus (CMV). There is no cure for CMV, and affected plants will need to be removed and destroyed.
These plants are also susceptible to brown spot fungus. Affected plants should be removed and destroyed, and the area should not be used to grow more lupines for several years to allow time for the ground spores to die off.
Powdery mildew can colonize plants in the rainy season, to the point where it is best just to cut damaged foliage away and wait for regrowth.
Landscape Uses for Lupine
Lupines are well-behaved plants that work well in the perennial border or cottage garden. Grow enough lupines for the vase, as their stiff hollow stems keep the flower spikes erect in arrangements. Cut the flowers when about 3/4 of the flowers are open for the longest-lasting arrangement.
The rich nectar stores of lupine blossoms make it a favorite of butterflies as well as bees. Plant them alongside other early summer butterfly favorites that thrive in similar conditions, like poppies, penstemon, or alliums.
Native Blue Lupine
The blue lupine (Lupinus perennis), or sundial lupine, is a native species of lupine with 4- to 10-inch blue flowers and a total height of about 2 feet. It is native to the eastern United States and is the only known host plant for the Karner blue butterfly (Lycaeides melissa samuelis), an endangered species. Growing blue lupine is similar to that of the hybrid plants.