• AGM plants

    AGM plants have been through a rigourous trial and assessment programme. They are:

    • Excellent for ordinary use in appropriate conditions
    • Available to buy
    • Of good constitution
    • Essentially stable in form & colour
    • Reasonably resistant to pests & diseases

Penstemon hartwegii

Scarlet beard tongue

AGM plants

AGM plants have been through a rigourous trial and assessment programme. They are:

  • Excellent for ordinary use in appropriate conditions
  • Available to buy
  • Of good constitution
  • Essentially stable in form & colour
  • Reasonably resistant to pests & diseases
Scarlet beard tongue

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  • Other common names Scarlet beard tongue
    Hartweg penstemon

  • 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

  • Family Plantaginaceae / Plantaginaceae

  • Species P. hartwegii is a bushy semi-evergreen perennial to 70cm in height, with narrow foliage and panicles or racemes of slender bright crimson flowers 4cm in length, marked white in the throat and borne on purple stems

Characteristics

  • Foliage Semi-evergreen

  • Habit Clump-forming

  • 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)
    Old hardiness ratings

    While we update our systems with the new hardiness ratings you may still see old hardiness ratings in your search results. These are denoted as 'Old'.

    • H1 - Requires heated glass
    • H2 - Requires unheated glass
    • H3 - Hardy outside in some regions of the UK
    • H4 - Hardy throughout the UK
    • H1 + H3 - Requires heated glass but may be grown outside in summer

    For full details of the hardiness ratings see

    see more

    H4

Colour

Sunlight

  • Full Sun

  • Aspect South-facing or East-facing or West-facing

  • Exposure Sheltered

Soil

  • Chalk

    Chalk

  • Chalk

    Loam

  • Chalk

    Sand

  • MoistureWell-drained

  • SoilChalk, Loam, Sand

  • pHAcid, Alkaline, Neutral

Size

  • Ultimate height

    0.5-1 metres

  • Ultimate spread

    0.1-0.5 metres

  • Time to ultimate height

    2-5 years

How to grow

Cultivation Grow in fertile, well-drained soil in a sheltered position in full sun or partial shade. In cold areas, protect plant overwinter with a dry winter mulch

Propagation Propagate by softwood cuttings in early summer or semi-hardwood cuttings in midsummer. Propagate by division in spring

Suggested planting locations and garden types Flower borders and beds City & Courtyard Gardens Cottage & Informal Garden

How to care

Pruning Deadhead after flowering to maintain vigour, then cut back to base in winter

Pests May be attacked by slugs, snails and chrysanthemum eelworms

Diseases May be subject to a downy mildew

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