Old-fashioned lupines, or Lupinus arboreus, are easy to grow. Established plants can be expected to produce large, showy spikes that emerge in early summer for years to come. They're tall and impressive, and attain a mature size of up to 3 feet tall and 3 feet wide. Nearly carefree, lupines will benefit from a little pruning during the growing season.
Deadhead lupine flowers as they fade. This will encourage a second flush of blooms later in the season. Use sharp, clean shears or clippers to cut the spent flower stalk back to the first set of healthy leaves directly below the flower.
Choose a blooming stalk on each plant to be allowed to remain for seed production, if you wish. These plants will easily reseed themselves from spent flowers left on the plants.
Use sharp, clean pruning shears or clippers to cut the entire lupine plant back by one-half in early spring.
Continue watering lupine plants until they begin to die back in midsummer. This will prolong the lush appearance of the foliage.
Take stem cuttings in late summer when the weather begins to cool, if desired.