Thermopsis montana

RHS Plant Profile
false lupin

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false lupin RHS
false lupin RHS
Herbaceous Perennial
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A suckering herbaceous perennial, up to 90cm high, with silky, silvery blue-green leaves with three oval leaflets, and spikes of yellow broom-like flowers in early summer and sometimes again in early autumn

Position

Full sun, Partial shade

Soil Types

Chalk, Loam, Sand

Max Height

0.5-1 metres

Max Spread

0.5-1 metres

Size

Time to Maturity
2–5 years
Max Spread
0.5-1 metres
Max Height
0.5-1 metres

Growing Conditions

Chalk Loam Sand
Moisture
Moist but well–drained
pH
Acid or Alkaline or Neutral

Position

Full sun Partial shade
Aspect
South–facing or West–facing or East–facing
Exposure
Exposed or Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

  • H1A: under glass all year (>15C)
  • H1B: can be grown outside in the summer (10 - 15)
  • H1C: can be grown outside in the summer (5 - 10)
  • H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
  • H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
  • H4: hardy through most of the UK (-10 to -5)
  • H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
  • H6: hardy in all of UK and northern Europe (-20 to -15)
  • H7: hardy in the severest European continental climates (< -20)
H6

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Fabaceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Suckering
Potentially harmful
Harmful if eaten. Wear gloves and other protective equipment when handling Pets (dogs): Harmful if eaten - for further information and contact numbers regarding pets, see the HTA guide to potentially harmful plants
Genus
Thermopsis are lupin-like rhizomatous herbaceous perennials with erect stems, leaves with three leaflets, and yellow or purple flowers
Name Status
Correct
Plant Range
NW USA

How to Grow

Cultivation

Grow in well-drained soil in sun or partial shade. Can spread quickly and has the potential to become a nuisance. Dig out roots if the plant spreads into unwanted areas

Propagation

Propagate by seed or division in spring

Suggested planting locations and garden types

  • Cottage and informal garden
  • Prairie planting
  • Banks and slopes

Pruning

No pruning required, but if the faded flower spikes are cut down to just above ground level there may be a second flush of flowering in early autumn

Pests

Generally pest-free

Diseases

Generally disease-free