Agastache nepetoides

RHS Plant Profile
yellow giant hyssop

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Herbaceous Perennial
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A tall perennial, up to around 2m high, with stout, square stems and aromatic, coarsely toothed green leaves up to 15cm long. Dense spikes of tubular, pale greenish-yellow flowers are produced in late summer

Position

Full sun, Partial shade

Soil Types

Chalk, Clay, Loam, Sand

Max Height

1.5-2.5 metres

Max Spread

0.5-1 metres

Size

Time to Maturity
2–5 years
Max Spread
0.5-1 metres
Max Height
1.5-2.5 metres

Growing Conditions

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

Position

Full sun Partial shade
Aspect
East–facing or South–facing or West–facing
Exposure
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)
H3

Colour & Scent

Fragrance Foliage
Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Lamiaceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Columnar upright
Genus
Agastache are herbaceous perennials with simple, aromatic leaves and small 2-lipped tubular flowers in whorls forming dense spikes, in summer and autumn; some are rather tender but can be grown as annual bedding
Name Status
Correct
Plant Range
E Canada, Central USA

How to Grow

Cultivation

Thrives in fertile, moist but well-drained soil in sun or light shade. Dislikes summer drought

Propagation

Propagate by seed or by division in spring. Will self-seed in place in good conditions

Suggested planting locations and garden types

  • Architectural
  • Cottage and informal garden
  • Wildlife gardens
  • Flower borders and beds

Pruning

Remove spent flowering spikes as they fade

Pests

Generally pest-free

Diseases

May be susceptible to powdery mildews