• 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

Gunnera manicata

giant rhubarb

  • Other common names giant rhubarb
    Chilean rhubarb

    prickly rhubarb

    see more
  • Family Gunneraceae

  • Genus Gunnera may be evergreen or herbaceous rhizomatous perennials, and range from small creeping plants to very large with huge leaves. The flowers are small, borne in narrow panicles or spikes and may be followed by small berry-like fruits

  • Details G. manicata is a very robust herbaceous perennial, forming a spreading clump of lobed, rounded, rough-textured leaves with spiny stems 1-2m in width. Tiny red-brown flowers are borne in erect panicles to 1m in height

  • Plant range Brazil


  • Foliage Deciduous

  • 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)




  • Full Sun

  • Partial Shade

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

  • Exposure Sheltered


  • Clay


  • Loam


  • MoisturePoorly-drained

  • SoilClay, Loam

  • pHAcid, Alkaline, Neutral


  • Ultimate height 1.5-2.5 metres

  • Ultimate spread 2.5-4 metres

  • Time to ultimate height 5-10 years

How to grow

Cultivation Grow in permanently moist, humus-rich soil in full sun or partial shade. Shelter from cold drying winds. Protect crowns by mulching during the winter months. This plant is listed on Schedule 3 of the EU (Birds and Natural Habitats) Regulations 2011 in the Republic of Ireland as an invasive non-native species. While this does not prevent it from being sold or from being grown in gardens in the Republic of Ireland, the RHS encourages those that do grow it to take great care with managing it and with disposing of unwanted material. The RHS also encourages gardeners in the Republic of Ireland to find alternative plants to grow to those listed on Schedule 3

Propagation Propagate by seed sown in gentle heat as soon as ripe, seed quickly loses viability. Propagate by cuttings of leafy, basal buds in spring

Suggested planting locations and garden types Architectural Cottage & Informal Garden City & Courtyard Gardens

How to care

Pruning Cut back after flowering

Pests Generally pest free

Diseases Generally disease free

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