Members of the family Fabaceae, lupins can come in annual and perennial varieties and grow tall spikes of sweet-pea-shaped flowers. These deer-resistant blooms prefer partial shade to full sun. Lupin flowers propagate from seed and prefer to grow in USDA hardiness zones 5 through 8, depending on the variety, in well-drained soil with a pH between 4.5 and 7.5. Far from fussy, lupin flowers display their red, white, yellow, blue or violet blooms in the spring and summer with minimal care once established.
Maintain moist soil after planting and throughout the growing season. Use a soaker hose, which will deliver deep watering down to the roots of the lupin flowers. Lupins require at least 1 inch of water per week through both supplemental watering and rain.
Feed the lupin flowers a diet of fertiliser that is rich in phosphorous and low in nitrogen. Follow the label instructions for application recommendations. Most lupins thrive when given a dose of fertiliser once a month during the growing cycle.
Deadhead the flowers regularly. Snip them just below the flower; they will re-bloom. If you are growing perennials, cut the flower stalks down to the base after flowering is over.
Remove pests from the lupin flowers using an insecticidal soap. Although lupins have few pest problems, they are prone to aphid infestations now and then. Apply the insecticidal soap according to manufacturer's instructions.
Spread mulch around the lupin flowers to control weeds. Weeds will compete with the lupins for water, so a three- to four-inch layer of straw or bark chips can help control the problem. Mulching will also protect the roots of the lupin flowers and improve drainage.
Collect the seeds of your lupin flowers in the fall to grow more the following spring. Pick the seedpods when they turn yellow. Peel the pods open and pour the seeds into a plastic bag. Place a damp paper towel in the bag, seal and store in the refrigerator until spring.
Do not overwater your lupins. Standing pools of water above and below the soil can cause root rot. If the soil already feels moist to a one-inch depth, do not add more water.