Penstemon serrulatus

RHS Plant Profile
cascade penstemon

Save a plant

Where do you want to save Penstemon serrulatus?

Plants I own
Wishlist
Go to My Plants
cascade penstemon RHS / Joanna Kossak
cascade penstemon RHS / Joanna Kossak

Other common names

coast penstemon, serrulate beardtongue, serrulate penstemon

Synonyms

Penstemon diffusus

RHS Recommended

Plants for pollinators
Herbaceous Perennial
Buy this from Plant Nurseries
1 Suppliers

A semi-evergreen subshrub to 50cm, with glossy, oval to lance-shaped, dark green leaves. Broad, dense, one-sided clusters of narrowly bell-shaped, pinkish-purple flowers are produced in late summer

Position

Full sun

Soil Types

Chalk, Loam, Sand

Max Height

0.1-0.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
2–5 years
Max Spread
0.1-0.5 metres
Max Height
0.1-0.5 metres

Growing Conditions

Chalk Loam Sand
Moisture
Well–drained
pH
Acid or Alkaline or Neutral

Position

Full sun
Aspect
West–facing or South–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

RHS Recommended: for People & Planet

RHS Recommended Plants for People & Planet

For Water Resilience

Plants for Flood Resilience

Plants that can help manage heavy rain by catching rainfall, slowing surface run-off, encouraging water into the soil or taking it up through their roots, contributing to flood resilient gardens.

Plants for both Wet and Dry Conditions

Plants that cope with changing soil moisture, including wet winters and extended summer dry. Once established, they grow as wet and dry conditions alternate.

For Temperature Resilience

Plants for Temperature Cooling

Plants that cool air temperature by providing shade, transpiration, or reflection to reduce heat impact on people, animals, soil or other ground surface.

Plants for Wind Shelter

Plants with dense canopies often grown as a tall thick hedge or grouping can block wind and shelter gardens, buildings and people.

For Carbon Storage

Plants for Carbon Storage

Plants that can take up carbon (CO₂) through photosynthesis and store it within the plant or deposit it by their roots into the soil.

For Biodiversity

Plants for Pollinators

Plants that have flowering properties (pollen and/or nectar) that are particularly beneficial for pollinating insects such as bees, butterflies and hoverflies.

Growing conditions for maximum benefit

This plant will provide the maximum benefits if it is healthy and allowed to grow to maturity

For Bio-Diversity

  • Plants for Pollinators

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Plantaginaceae
Native to GB/Ireland
No
Foliage
Semi evergreen
Habit
Bushy
Genus
Penstemon may be deciduous or evergreen perennials or subshrubs, with simple, narrow leaves and racemes or panicles of bell-shaped or funnel-shaped flowers in summer and early autumn
Name Status
Correct
Plant Range
W North America

How to Grow

Cultivation

Grow in very gritty, sharply-drained soil in full sun. In cold areas, protect plant overwinter with a dry winter mulch. See penstemon cultivation for further advice

Propagation

Take softwood cuttings in early summer or semi-ripe cuttings in midsummer. Divide in spring or propagate by seed in late winter or spring

Suggested planting locations and garden types

  • Cottage and informal garden
  • City and courtyard gardens
  • Coastal
  • Gravel garden
  • Wildlife gardens
  • Flower borders and beds

Pruning

deadhead after flowering

Pests

Maybe susceptible to slugs, snails, aphids and leaf and bud eelworm

Diseases

May be susceptible to grey moulds, Powdery mildews and fungal leaf spot