How to Grow Thermopsis Plants

Guide to Growing Goldenbanner, Carolina lupine, and Aaron's Rod

Thermopsis are hardy perennials that range from 30 cm to 1.5 m in height.

They bloom from late spring to summer and carry yellow flowers resembling those of peas.

Some common names for Thermopsis include goldenbaner, Aaron's rod, False Lupine, and Carolina Lupine.

Thermopsis montana
Thermopsis montana by peganum.

Quick Thermopsis Growing and Care Guide

  • Common Names: Goldenbanner, Carolina lupine, Golden bean, wet tooth, False lupine, Mountain thermopsis.
  • Life Cycle: Hardy perennial.
  • Height: 12 to 60 inches (30—150 cm).
  • Native: North America, East Asia.
  • Growing Region: Zones 3 to 9.
  • Flowers: Late spring through to summer.
  • Flower Details: Yellow. Pea-like. Terminal racemes. Erect stalks. Similar to lupines.
  • Fruit: Legume pod. Villous.
  • Foliage: Herbaceous. Clump forming. Greyish-green. Compound. Oval leaflets.
  • Sow Outside: Cover seed. Start of spring - before the last light frost, or towards the end of autumn.
  • Sow Inside: : Germination time: two to four weeks. Temperature: 70°F (21°C). First chip seeds, soak for a day in warm water, then sow in peat pots. Seven or eight weeks before the expected last frost. Transplant outdoors following the last frost. Space at 18 to 24 inches (45—60 cm).
  • Requirements and care: Full sunlight or light shade in hot areas. Good drainage. Acidic to neutral soil pH 5.5 to 7. Gritty soil for best results, but tolerant of most soil types. Can survive in dry soils. Deadhead to promote second bloom. Provide support. Cut back to the ground in autumn. Long taproots make it difficult to transplant. Propagate: by division in the spring.
  • Miscellaneous: Toxic if ingested. Traditionally used by Native Americans to produce yellow dye and as an infusion to treat stomach disorders, especially in horses.

How to Grow Thermopsis Species such as Goldenbanners and Aaron's rod

The seeds of Thermopsis plants should be sown outdoors just before the last frost of spring or late on in autumn. Once sown, lightly cover the seeds.

Ideally they should be grown in a sunny or partially shaded area of the garden that has a gritty soil of pH 5.5 to 7.

If starting off indoors then sow Goldenbanners, Aaron's rod, and similar seeds into peat pots about seven weeks before the last frost is expected.

The seeds should first be chipped and need to be imbibed by soaking in warm water for a day. It should take from two weeks to a month for them to germinate. Once established plant the young plants outdoors following the last frost of spring at about 50 to 60 cm apart.

Caring for Thermopsis

It is easy to care for Thermopsis plant species - taller varieties should be staked in windy areas; remove the flowering stalks once they have finished flowering to allow for a second bloom; cut back to the ground in the autumn.

If you require more plants it is probably best to grow from seeds as the plants have a delicate taproot; however if you prefer to you can propagate by division in the spring.

Common Types of Thermopsis

Some of the main species of this plant are Thermopsis lanceolata, Thermopsis montana, Thermopsis villosa, Thermopsis caroliniana, and Thermopsis rhombifolia.

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