How to Grow and Care for Texas Bluebonnet (Lupinus texensis)

The beloved wildflower and state flower of Texas, the Texas Bluebonnet (Lupinus texensis) can cross the state line and become a star in many of your gardens. Easily propagated from seed, this annual plant related to lupines is hardy in USDA zones 4-8.

The appeal of the Texas bluebonnet is the clusters of bright blue pea-like flowers topped with a cap of white blooms. These attractive pollinator plants bloom in springtime in sunny fields and along roadsides and in full-sun garden plantings. The plants are self-seeding or can be started by sowing seeds in the fall.

The seeds can cause contact dermatitis when handled and all parts of the plant are toxic if ingested by cats, dogs, horses, grazing animals, and humans.

When to Sow Bluebonnet Seeds

Because Texas bluebonnets are cold hardy annuals that bloom in the spring, the seeds should be sown in October through November. The temperatures in the hardiness zones of early autumn will help the seeds germinate, and the colder weather is needed to help the root structure of the bluebonnets develop so bloom occurs the following spring.

The multi-colored seeds are small and flat. While commercially-sold seeds will germinate quickly, collected seeds are harder to germinate. Not every seed will germinate when planted but might grow in a few months. The delayed germination helps ensures species survival under adverse growing conditions like prolonged drought. Commercially-sold seeds are treated to weaken the seed coating or scarified so the seeds will germinate within 10 days of planting.

Texas Bluebonnet Care

As a native wildflower, the Texas bluebonnet is not a fussy plant. It has evolved to survive in harsh conditions like drought and poorly nourished soil. The key to success in home gardens is to plant the seeds or seedlings in an area with full sun, don't overwater it, plant it in well-draining soil, and don't overfertilize it. In other words, leave the plants alone! Bluebonnets are accustomed to thriving in harsh Texas conditions.

The bluebonnets usually begin to bloom around the end of March and continue for about a month. Around mid-May, a green seedpod is formed. The seedpod will turn yellow and then brown. When the seeds mature, the pod will pop open and release the small hard seeds that will form next year's blooms.

Light

Texas bluebonnets will thrive in full-sun areas with eight to ten hour hours of sun per day. While they can tolerate partial shade, fewer blooms will be produced.

Soil

The plants will thrive in any type of soil—sandy, loam, clay, chalk—if the area drains well. Soil pH is important but they will do best in a slightly alkaline growing medium.

Water

The most important time to provide water to Texas bluebonnets is when the seed is sown. The soil should be kept moist—not soggy—until the seed germinates. Then, do not water established plants until the top one inch of soil dries, then water moderately. Do not allow the ground to remain wet.

Temperature and Humidity

Texas bluebonnets need the warm fall temperatures to help the seeds germinate and the cooler winter weather temperatures to help develop the root system required to produce early spring blooms. By the time the high humidity of summer arrives, the visible parts of the plants have died back and are not affected. Texas bluebonnets will thrive in USDA hardiness zones 4-8.

Fertilizer

As a wildflower, Texas bluebonnets do not require supplemental fertilization. Adding a nitrogen-rich commercial fertilizer will often reduce bloom production by causing the leaves to absorb most of the nutrients.

Bluebonnets are a legume that has roots that use a bacterium in the soil called Rhizobium to improve plant growth and flowering. Rhizobium enhances nitrogen fixation, the conversion of atmospheric nitrogen to a form usable by plants. Once the bluebonnet plants are established, nodules (small, rounded lumps containing nitrogen-fixing bacteria) on the roots.

Types of Bluebonnets

While Lupinus texensis is most likely the most recognizable, commercially available, and easiest to grow bluebonnet, four other types of bluebonnets are also the state flower of Texas.

• Lupinus subcarnosus: Grown in the deep sandy loams from Leon County southwest to LaSalle County and down to the northern part of Hidalgo County, it is often called the sandy land bluebonnet. The plant's leaflets are blunt, sometimes notched with silky undersides. This species, which reaches peak bloom in late March, is not easy to maintain in clay soils.

• Lupinus Havardii: A larger bluebonnet with flowering spikes up to three feet tall, it is known as the Big Bend or Chisos Bluebonnet. Found on the flats of the Big Bend country in early spring, it is difficult to cultivate outside its natural habitat.

• Lupinus concinnus: The smallest bluebonnet at two to seven inches tall, the flowers are a combination of white, rosy purple, and lavender. Blooming in early spring, it is found sparingly in the Trans-Pecos region.

• Lupinus plattensis: Found in the Texas Panhandle's sandy dunes, it is the only perennial species in the state. Growing to about two feet tall, it blooms in mid-to-late spring and is known as the dune bluebonnet, the plains bluebonnet, or the Nebraska Lupine.

Pruning

The Texas bluebonnet requires no pruning; however, removing spent early blooms might encourage the production of side shoots and blooms. When the plant has completed the blooming season and dies down, it can be cut down to the ground or, if planted in a field, mowed to the ground. It is best to wait until the seed pods have formed and dried before cutting back the plants.

How to Grow Texas Bluebonnets From Seed

While you might be able to find seedlings at a specialized wildflower nursery, most gardeners start their Texas Bluebonnets from seed. The seed can be sown directly into the ground or started in a covered seed starter.

Seeds should be planted in October or November so the plants have time to develop root systems during the cooler temperatures of winter. It requires nearly one year for the bluebonnets to go from seed to plant/flower to seed again. Collected seeds or those sown naturally after the seedpod has popped have a low germination rate and can take a couple of years for mature plants to develop. For more reliable production, choose seeds offered commercially or scarify collected seeds.

1. To scarify the seeds, physically nick the seeds with a knife (for small quantities) or rub the seeds with sandpaper or freeze the seeds overnight, then quickly pour boiling water over the seeds and soak them for several hours at room temperature.

2. Once scarified, plant the seeds in a moist seed-starting mixture where they will germinate quickly. Keep watered for several weeks, especially if the weather is dry.

3. Once the seedlings have developed several leaves, transplant them into the garden and reduce the amount of watering because the plants are drought tolerant.

When planting a bluebonnet transplant, be careful not to plant it too deeply. You will notice that all of the leaves emerge from a central crown-like structure. This crown should not be buried, otherwise, the plant will rot. If you are sowing seeds directly into the garden, plant eight to ten seeds per square foot. Not every seed will germinate. Use your hands to press the seeds firmly into the tilled, loose soil.

Choose a sunny, well-drained location with slightly alkaline soil; south and west-facing slopes will encourage earlier spring growth and flowering.

Although bluebonnet seeds require some moisture to germinate and grow, they do not like saturated soil. If fall or winter rainfall is low, occasional watering will help ensure success.

Overwintering

Once the seeds or seedlings are planted in the fall, the process of overwintering is simple: leave them alone. Bluebonnets form ground-hugging rosettes that are only a few inches tall but can spread up to 12 inches. This is a natural habit and the plant will not grow rapidly until the warmth of spring initiates flower stalks. The lower leaves can turn a crimson color after the first freeze. Beneath the rosette of leaves, a large mass of roots is growing.

Common Pests and Plant Diseases

The most common insect pests that can destroy seedlings and transplants are pillbugs and sowbugs. These bugs usually attack at night and eat the plants. To ensure seedling and transplant survival, reduce moisture, remove excessive mulch, and if needed, scatter pillbug bait around the newly established or emerging plants during the first month after planting.

Damping off, a fungal disease that causes stem rotting, can occur with seedlings. To minimize damping off problems, avoid planting in beds with a history of this condition, use transplants rather than direct seeding into the bed, and do not overwater.

How to Get Texas Bluebonnets to Bloom

Blooming is most abundant if the bluebonnets are planted in an area with full sun. Avoid overwatering and over-fertilization. If the seed-starting or planting is started in the spring instead of the previous autumn, the plants will not bloom at all or will have sparse blooms. Timing is everything.

Common Problems With Texas Bluebonnets

• Overwatering

• Over-fertilization

• Too much shade

• Pillbugs and sowbugs eating young plants

• Planting seeds or seedlings in the spring

Frequently Asked Questions

Do bluebonnets only grow in Texas?

A wildflower, bluebonnets can be found growing wild in Florida, Louisiana, and Oklahoma as well as Texas. Texas Bluebonnets can be cultivated in home gardens in hardiness zones 4-8.

Are bluebonnets poisonous to touch?

All parts of the bluebonnets, especially the seeds, can cause contact dermatitis when touched. It is recommended to wear gloves when handling the plant. The entire plant is toxic to dogs, cats, horses, grazing animals, and humans if ingested in large quantities.

What are bluebonnets used for?

In the wild, bluebonnets provide spectacular spring shows in meadows. Their legume-like roots help prevent soil erosion in fields and along roadsides. In the home garden, they provide stunning early spring blue flowers and are particularly lovely when underplanted with pansies.