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Herbaceous Perennial

Agastache 'Summer Sky'
  • RHS Plants for pollinators

giant hyssop 'Summer Sky'

'Summer Sky' is a compact, bushy perennial to 60cm tall with ovate, aromatic leaves. Flower spikes comprising whorls of small, tubular, violet-blue flowers with darker calyces are borne from summer into autumn

Size
Ultimate height
0.5–1 metres
Time to ultimate height
2–5 years
Ultimate spread
0.1–0.5 metres
Growing conditions
Chalk
Loam
Sand
Moisture
Moist but well–drained, Well–drained
pH
Acid, Alkaline, Neutral
Colour & scent
StemFlowerFoliageFruit
Spring Green
Summer Blue Purple Green
Autumn Blue Purple Green
Winter
Position
  • Full sun
Aspect

South–facing or West–facing

Exposure
Sheltered
Hardiness
H3
Botanical details
Family
Lamiaceae
Native to the UK
No
Foliage
Deciduous
Habit
Bushy
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

Accepted

How to grow

Cultivation

Grows best in well-drained, fertile soils in full sun

Propagation

Propagate by division or by semi-ripe cuttings

Suggested planting locations and garden types
  • City and courtyard gardens
  • Gravel garden
  • Patio and container plants
  • Cottage and informal garden
  • Flower borders and beds
Pruning

Remove spent flowering spikes through the season to prolong flowering

Pests

Generally pest-free

Diseases

May be affected by powdery mildews

Get involved

The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.