• AGM plants

    AGM plants have been through a rigorous 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

Grevillea robusta

silky oak

AGM plants

AGM plants have been through a rigorous 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
silky oak

© � RHS 2002

  • Other common names silky oak
    silky-bark oak

    silk oak

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  • Genus Grevillea can be evergreen shrubs or trees, with alternate, simple or pinnately divided leaves and petal-less flowers consisting of a colourful calyx tube with protruding style, borne in racemes or panicles

  • Family Proteaceae / Proteaceae

  • Details G. robusta is a fast-growing evergreen tree to 20m or more, but is usually grown as an annual for foliage effect making a bushy shrub to 3m. Olive-green, fern-like leaves to 30cm in length, paler beneath. Racemes of tubular yellow flowers are produced only by mature plants

  • Plant range E Australia

Characteristics

  • Foliage Evergreen

  • Habit Bushy

  • Toxicity

  • 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

    H1c

Colour

Sunlight

  • Full Sun

  • Aspect South-facing or West-facing

  • Exposure Sheltered

Soil

  • Chalk

    Loam

  • Chalk

    Sand

  • MoistureMoist but well-drained, Well-drained

  • SoilLoam, Sand

  • pHAcid, Neutral

Size

  • Ultimate height

    Higher than 12 metres

  • Ultimate spread

    4-8 metres

  • Time to ultimate height

    20-50 years

How to grow

Cultivation Grow outdoors in acid to neutral well-drained soil in a frost-free area or as part of a summer bedding scheme. Grow under glass in lime-free compost with added grit in full light. May need restrictive pruning under glass

Propagation Propagate by seed, semi-hardwood cuttings or graft

Suggested planting locations and garden types Patio & Container Plants

How to care

Pruning Pruning group 1 outdoors, but more rigorous pruning may be necessary indoors to restrict size

Pests Generally pest free

Diseases Generally disease free

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