False lupines are related to peas, true lupines, and baptisias. The plants have attractive pea-like foliage and spikes of yellow flowers resembling large yellow lupines in early summer. These plants do well in the back of the border and work well as cut flowers.

Plant facts

  • Common name: False lupine
  • Botanical name: Thermopsis caroliniana
  • Zones: 4 to 9
  • Size: To 4½ feet tall
  • From: Areas of North America
  • Family: Fabaceae (pea family)


Growing conditions

  • Sun: Full sun
  • Soil: Moist, but well-drained soil is best. The plants adapt to a range of soil conditions.
  • Moisture: Plants are drought tolerant.


Care

  • Mulch: A 2- to 3-inch-deep layer of mulch around the plants may be beneficial, especially in warm-summer areas. This layer of mulch helps conserve soil moisture and prevents the soil temperature from rising too rapidly.
  • Pruning: Cut down dead stalks in autumn after they freeze or in early spring before the plants begin to grow.
  • Fertilizer: In soils rich in organic matter, extra fertilizer isn't usually necessary. In other soils, use a general-purpose fertilizer in spring.
  • Staking: To stake the tall plants, sink a tall stick or stake into the ground a short distance from the plant (so to not harm the root system). Tie the plant stem to the support. It is best to use a figure-eight pattern to tie the plant-with the stem in one loop and the stake in the other. This helps prevent against excessive rubbing, which can cause disease problems.


Propagation

  • Seedlings: Carefully remove the young plants from around the base of the mother plant. Ensure they have a good root system.
  • Seed: Sow fresh seed outdoors in a sheltered spot or in a cold frame or store it inside in a cool, dry place and sow it outdoors in early spring.
  • Divison: Carefully dig large clumps and separate rooted shoots. Because of their large root system, division isn't the preferred form of propagation.


Pests

  • False lupines are largely disease- and insect-resistant, especially if sited well.

Garden notes

  • The plants develop large, almost woody root systems and can be very difficult to transplant. It's best to site them in a permanent spot instead of trying to move them in a couple of years.
  • False lupines resent root disturbance and may not flower for a season or two after transplanting.
  • If the seed capsules are left to dry on the plants, false lupines may self-seed.