How to Grow and Care for Lupine (Bluebonnet)

The lupine flower, also known as lupin or bluebonnet, looks like a wildflower, but it is a fast-growing legume in the pea family that has a tall, showy spire of colorful blooms that are typically purple. Flowers bloom from spring through midsummer and, while individual lupine plants do not spread, the flower pods each disperse up to a dozen seeds.

Lupine is an annual and short-lived perennial flower with a lifespan of two to five years. This low-maintenance plant grows best in northern climates with cooler summers and requires a daily six hours of full sunlight, weekly watering, and soil on the acidic side. These vividly colored flowers are also deer-resistant and beneficial to pollinators like bees and butterflies. The plant is toxic to humans and animals.12

Lupine Care

Here are the main care requirements for growing lupine:

• Plant lupines during cooler early spring or fall temperatures.
• Use loose, sandy soil for lupines, and avoid planting this flower in clay soil unless it is amended.
• Offer lupines more sun and minimum shade.
• Space smaller lupines a foot apart and larger ones two to three feet apart.
• Stake taller lupine varieties using grow-through grid stakes to prevent them from flopping over. 
• Water lupine during periods of dry weather.
• Use an acidifying, phosphorous-heavy fertilizer when planting lupine.
• Deadhead lupine to encourage continuous flowering.
  

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Planting

To grow lupine seedlings, dig holes 1 to 1 1/2 feet deep and start small plants about 1 foot apart, while larger plants should be grown two to three feet apart. Ideally, lupine plants are planted outdoors in cooler temperatures, either early spring or fall. Add mulch but avoid fertilizer.

Light

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 diminish. However, some afternoon shade is ideal in hot climates.

Soil

These flowers thrive in organically rich soil or loose, sandy soil with sharp drainage. They prefer a neutral to slightly acidic soil pH, though they also can grow in very acidic soil conditions. Lupines will typically not survive in heavy clay soil unless the dirt is loosened a few inches down and heavily amended with compost.

Water

While lupines don't like soggy soil, which can cause root rot, they prefer regular watering. Water at least weekly if you haven't gotten rainfall to prevent the soil from drying out.

Temperature and Humidity

Lupines like fairly cool summers and don't bloom well in the hot, humid climates of the southern part of the United States. Place a light layer of mulch around the lupines to retain soil moisture and keep the roots cool in hot areas.

Fertilizer

Lupines generally don't require fertilizer, and too much fertilizer can encourage excess foliage growth rather than blooms.4 However, an acidifying fertilizer with more phosphorous than nitrogen is useful for lowering the soil pH of alkaline soils. These fertilizers may be labeled as "bloom boosters."5 Lupine already fixes the nitrogen in the soil, so it doesn't require more.

Types of Lupine

The types of lupine 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 (also called large-leaved lupine), a North American native, crossed with various other species, such as Lupinus arboreus.

Although rainbow hybrid lupine seed mixes are the most popular commercially available lupine, the original blue strain is the hardiest. 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. For example, 'Gallery White' boasts snowy white flower spikes.
• 'Dwarf Lulu': These plants grow about 2 feet tall in a rainbow of hues and feature unusually dense racemes.
• 'Minarette': This dwarf 18-inch variety of lupine looks stunning in drifts along a border's edge or in containers.
• Lupinus albus (white lupine): This taller lupine can grow up to 4 feet tall with white blossoms.
• Lupinus albifrons (silver lupine): This taller lupine grows between 3 to 5 feet tall with silver-green leaves topped with pale blue to purple flowers.
• Lupinus angustifolius (blue lupine): Also called narrowleaf lupine, this taller plant grows to 5 feet tall and has blue blooms. It is used more for agricultural use than for gardens.

Propagating Lupines

Because lupines sprout so easily from seed, this is the normal method for growing them though blooming takes longer. Lupines can also be propagated by carefully taking basal cuttings from established plants in the spring and simply replanting them. Basal propagation ensures an ongoing stock of the plants and they may bloom sooner than seeds. Take these steps:

1. Propagate lupine cuttings in the early spring before the plant has begun to actively grow and leaf out.
2. Use a sanitized sharp knife to sever a segment of the crown and roots from the parent plant.
3. Transplant the new segment to a new location in the ground.
4. Propagate lupine every two to three years, as they are short-lived plants.

How to Grow Lupine From Seed

Lupines are easy perennials to grow from seeds but can take two years to bloom this way. Buy lupine seeds or harvest the small round tan or green seeds from the plant's pods in the fall. Start lupines from seed in the early to late spring or late fall for the following spring season. Take these steps:

• Before sowing in the ground, nick the tough seed coat or soak it in water overnight to ensure a better germination rate.
• 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.

Potting and Repotting Lupine

Plant lupine in pots in the springtime. Choose a large, deep, and heavy container to comfortably handle the plant's long taproots and top-heavy, upright growth. Use well-draining soil, space lupine plants a minimum of a foot apart, and put the container in full sun. Cut the plant back and shelter the pot over the winter to help lupines survive.

Overwintering

During the winter, lupines die back to the ground and go dormant. Cut the lupine stalks down to the ground, leaving 1 to 2 inches above ground. Mulch to protect the below-ground plant from freezing temperatures as it overwinters.

Common Pests & Plant Diseases

Lupine is vulnerable to aphids are common in spring.6 Control pests with horticultural oils or pesticides.

Lupine is susceptible to lupine anthracnose which causes leaf blight and brown spots.7 Remove and destroy affected plants and avoid using the area to grow lupines for several years so the spores have time to die off. Powdery mildew from poor air circulation can impact lupines with white, powdery patches on foliage.8 Cut away the foliage and wait for regrowth or treat it with organic methods.

How to Get Lupine to Bloom

Bloom Months

Lupine blooms from late spring into July. If they do rebloom after their first flush, they may produce smaller flowers.

What Do Lupine Flowers Look and Smell Like?

Hybrid lupines have a telltale look of tall, showy spires of flowers that can come in a multitude of colors. The foliage resembles palm leaves with seven to 10 leaflet segments each. Lupines have sweet scents but various types smell different.

How to Encourage More Blooms

Lupines planted in deep shade typically won't flower. Remedy this by trimming back neighboring shrubs and trees for more sun. A second bloom in the summer may occur but with smaller flowers. Cut back in spring after the first flowering to encourage summer blooms.

What to Do With Lupine After It Blooms

Deadheading lupine after it blooms and fades may result in a second flush. By the fall, cut the plants down to the ground.

Common Problems With Lupine

Lupine is easy to grow but there may be a couple of problems. Here's what to look for.

Not Blooming

Your lupines may not be blossoming because they are not getting enough sunlight, the flowers are underwatered, there's a pest infestation, or the soil does not have enough phosphorous in it.

Brown Leaf Tips

Lupines are susceptible to a fungus called lupine anthracnose. The leaf tips of younger lupine plants turn brown and bend. As the disease develops, more brown spots and cankers appear on the leaves. Remove and discard all infected plants. To protect surrounding plants from the fungus, use a fungicide for outdoor ornamental plants or one for Colletotrichum diseases. Colletotrichum gloeosporioides cause Lupine anthracnose.7