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