How to Grow and Care for Lupine (Bluebonnet)

The lupine flower, also known as bluebonnet, may look like a wildflower, but it is a fast-growing legume in the pea family that just happens to have a tall, showy spire of colorful blooms that are typically purple, but can also be blue, white, or yellow. You can expect flowers for about 3 months, from spring through mid summer and, while individual lupine plants do not spread, you can expect flower pods to disperse up to a dozen seeds from each pod.

Lupine is available as both an annual and a perennial flower and grows best in northern climates with cooler summers, requires full sunlight of at least 6 hours a day, weekly watering, and soil on the acidic side. These brilliant flowers are also deer-resistant and beneficial to pollinators like bees and butterflies. Keep in mind that the plant is toxic to both humans and animals.

Lupine Care

Here are the main care requirements for growing lupine:

• Plant during cooler early spring or fall temperatures.
• Offer more sun and minimum shade.
• Stake taller varieties using grow-through grid stakes to prevent them from flopping over. 
• Water during periods of dry weather.
• Use an acidifying, phosphorous-heavy fertilizer.
• Deadhead to encourage continuous flowering.
  

Planting

If you choose to grow lupine flowers from seedlings, dig holes 1 to 1.5 feet deep and start small lupine plants about 1 foot apart, while larger plants should be grown 2 to 3 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 6 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.

Soil

These flowers thrive in 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.

Water

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 part of the United States. 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.

Fertilizer

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

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Types of Lupine

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.

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.
• '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.

Propagating Lupines

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 and simply replanting them. Basal propagation ensures that you'll have an ongoing stock of your favorite plants. Take these steps:

1. Prepare to propagate with 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 2 to 3 years, as they are short-lived plants.

How to Grow Lupine From Seed

Lupines are among the easiest perennials to grow from seeds. Perennial lupine flowers typically take 2 years to bloom when grown from seed. You can buy seeds or harvest seeds from lupine's seed pods in the fall. Start lupines from seed in the early to late spring. You can also plant them in the 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.
• Keep in mind that lupines do not transplant easily due to their long taproots.
• Expect germination in 14 to 30 days.

Potting and Repotting Lupine

Lupine looks lovely in container gardens. Plant them in pots in the springtime. Choose a large, deep, and heavy container to comfortably handle the plant's long taproots. Since lupine grows upright and is somewhat weighty, make sure the container is also hefty so it does not become top-heavy and topple over. Fill the container with well-draining soil. Space lupine plants a minimum of a foot apart. Put the container in full sun. These plants do not transplant well because of their taproots. They may survive in pots over the winter if you cut them back and shelter the pots.

Overwintering

During the winter, lupine dies back completely to the ground and goes dormant. This process begins as soon as the flowers turn to seed pods and, when fall weather begins to set in, you should cut the lupine stalks down to the ground, leaving only 1-2" above ground. This will eventually die back, too, and mulch can be used to protect the below-ground plant from freezing temperatures as it overwinters.

Common Pests & Plant Diseases

Lupine is vulnerable to several pests and diseases. Aphids are common in spring, as are slugs and snails. Respond to control pests with horticultural oils or pesticides as soon as you notice them.

Lupine is 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.

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?

Wildflower watchers everywhere celebrate when springtime lupines come into bloom and create colorful spikes in gardens. There is nothing subtle about the shape and color of 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 7 to 10 leaflet segments each. 

How to Encourage More Blooms

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. Sometimes a second bloom in the summer will occur but with smaller flowers. Cut back in spring after the first flower 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

Some types of lupines are susceptible to a fungus called lupine anthracnose. If you see the leaf tips of younger lupine plants turning brown and bending to look like a shepherd's crook, the plant may be afflicted with this disease. The disease develops into more brown spots and cankers. Remove and discard all infected plants and parts of plants. To help surrounding plants, use a fungicide for outdoor ornamental plants and/or Colletotrichum diseases (lupine anthracnose is caused by Colletotrichum gloeosporioides).