Bluebonnets in a Pot

Soil

• Adapted to the poor soils of the Texas Hill Country, bluebonnets do not do well in rich soil and on a rich fertilizer diet, which cause floppy growth and fewer flowers. The Lady Bird Johnson Wildflower Center advises using ordinary garden soil amended by compost, decomposed granite or sand for good drainage. Bluebonnets are legumes that need a symbiotic root bacteria (Rhizobium) for optimum growth. The bacteria form root nodules and can take nitrogen from the air to make it available to the plant. If you live in Texas, this bacteria is often already present in the soil. Elsewhere, you might want add a source of rhizobium inoculant to the soil or buy bluebonnet seeds already coated with the inoculant.

Seeds

• Flattened round bluebonnet seeds have a hard seed coats that can last for a long time. Seeds are programmed to germinate at varying times, with some seeds staying in the soil for several years before they sprout. For increased germination percentage, break through the seed coat, a process called scarification. Rub the seeds against sandpaper or nick through the seed coat with a sharp knife. Without scarification, only about 20 percent of seeds will germinate the first season.

Planting

• Plant seeds 1/8 inch deep in fall, from August to December. Locate containers in an area that gets 8 to 10 hours of sun a day. For a good display, allow 8 to 10 seeds per square foot. Seeds usually germinate within 7 to 30 days between 55 to 70 degrees Fahrenheit. In mild-winter areas, seedlings appear in fall, overwinter as small rosettes, and grow and bloom in spring. In cold winter areas, seedlings need protection from winter cold. Keep the soil moist but not soggy. Bluebonnets grow in containers such as 12-inch tubs, half-barrels and hanging baskets. Clay containers dry more quickly than plastic ones.

Plant Description

• Texas bluebonnets mature to heights of 8 to 24 inches, with five-parted green leaves and several branches, each of which bears a spike-like head of blue flowers. Florets cluster to form up each flower, and each floret displays five petals, including an erect banner petal that when white tells bees that nectar is available and that turns magenta with age. Cultivars with different flower colors exist. "Barbara Bush" is a selected strain of bluebonnets with lavender flowers. "Aggie Maroon" echoes the school color of Texas A&M University. Pink- and white-flowered cultivars are also available. After flowering, seed pods form along the flower stalk. When dry, the pods explode, ejecting seeds some distance from the mother plant.