Lupinus, commonly known as lupin, lupine, or as bluebonnet, is a genus of flowering plants in the legume family Fabaceae. The genus includes over 199 species, with centers of diversity in North and South America. Smaller centers occur in North Africa and the Mediterranean. Hardy in USDA zones 4-8, this plant’s flowering is best in full sun. Lupine flowers are cone shaped spikes of blossoms packed closely together above tall palmate foliage. The blooms are often bicolored with hues ranging from red, yellow, white, purple and blue. Offered as annuals or short-lived perennials, Lupine can grow 1-5 feet tall. Lupines are used as a tall focal point in mass plantings, cottage gardens, or wildlife gardens.
Lupine should be planted in the spring. Choose a location that gets full sun. Average soil that is well-draining and cooler temperatures are perfect growing conditions for this plant. Lupines have long taproots. In denser clay soil, you may need to loosen the soil and mix in compost. This will improve drainage and help the roots grow. Space each plant 2-3 feet apart. Water well after initial planting.
After initial planting, keep the soil evenly moist to help good root development. Once the Lupine is established, it will tolerate dryer conditions and will only need watering in times of drought. Lupines prefer cool temperatures, so it is important that the soil remains cool. Spreading a layer of mulch around the plant helps to preserve moisture and keeps the soil cooler. When watering, water slowly and deeply, allowing the soil to completely dry in between. Water at the base of the plant and avoid getting the foliage wet.
Lupine plants actually absorb nitrogen directly from the atmosphere. This is why they can grow in less than ideal soil conditions and generally do not need fertilizer. The lupine can even fix the nitrogen in soil which can help vegetable gardens and other nitrogen loving-plants. When newly planted, Lupines will appreciate manure or compost mixed into the soil. If you would like to encourage more blooms, use a light application of fertilizer once a month during bloom time. Use a fertilizer that is high in phosphorus. A nitrogen fertilizer will not promote flowering.
Lupines will flower for several weeks before seed pods form in the fall. Typically a care-free plant, Lupine will benefit from occasional pruning during bloom time. Deadheading spent flowers will encourage another round of blooming towards fall. Deadheading the plant before seed sets in will keep the seeds from dropping into the garden. The seeds of Lupine can be toxic to humans and animals. At the end of the growing season, when the leaves turn yellow, this plant can be cut to the ground.
Caring For Lupine in Pots
Because Lupine plants have long taproots, many gardeners do not grow this plant in pots. Lupines can however, grow successfully in containers. Because of its long roots, you will need to select a very large and deep container. Be sure that the pot has drainage holes, as Lupines like moist, well draining soil. Use a general potting soil and water well after planting. Once you see that roots are growing out of the bottom of the container, it is time to move to a larger pot. Moving the plant to a larger container will result in large blooms.
Winter Care for Lupine
After the Lupines last bloom, you can cut the seed pods off or gather the seed for another use. Allow the leaves of the Lupine to remain on the stalks, as the plant is building root reserves for next year’s flowering. Once the plant has wilted and died, you can cut the plant material away. Depending on the variety of Lupine plant, it may survive winter and bloom again in the spring. A layer of mulch around the plant will insulate the roots and maintain consistent soil temperature.