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Why it is a pest plant
Chilean rhubarb is an invasive large clump-forming herbafceous plant which grows up to 3 m high. It forms dense patches that exclude virtually all other plants. It has stout rhizomes and massive umbrella-sized leaves, which along with stems are covered in rubbery prickles. Overall the plant resembles a giant rhubarb. Chilean rhubarb was introduced to New Zealand from South America for its interesting form.
How to recognise Chilean rhubarb
Chilean rhubarb grows vigorously during spring and early summer, forming new stems, leaves and up to five yellow flower spikes which rise from the base of the leaves. G.manicata (up to 3 m high) is larger than G.tinctoria (up to 2 m high).
Flowers: In summer, tiny green flowers are formed on a large spike up to 1 m long. Flowers are followed by tiny fruit.
Fruit: It produces abundant tiny red fruit, which are dispersed by birds. Each spike can produce up to 80,000 seeds per head.
Leaves: Its leaves have 5 to 7 lobes and are hairy beneath, especially on the veins. G.tinctoria leaves are up to 1 m across while G.manicata leaves can be up to 2 m across. Both resemble rhubarb leaves in shape. Leaves and stems are covered in rubbery prickles.
Giant hogweed (Heracleum mantegazzianum)
Giant hogweed’s leaves are more deeply lobed. It has a tall flower stalks with large umbrella-like clusters of greenish-white flowers.
Responsibility for control
All land occupiers in the Waikato region are responsible for the total control of self propagated Chilean rhubarb on their property.
How to control Chilean rhubarb
For small patches: Dig out, taking care to get all root parts OR cut right back and treat the stumps with a concentrated herbicide in gel form (such as Vigilant). Deep bury or landfill seedheads and rhizomes. Other parts can be composted.
For large patches: Cut off the flower heads to prevent further seed dispersal and then spray the leaves well while in full foliage with a herbicide containing the active ingredient glyphosate (such as Roundup Renew Xtra) OR cut the plant right down to 10-20 cm stumps then apply herbicide concentrate (such as Roundup painted straight on or Vigilant gel). Repeat in following season where necessary.
When using herbicides
• read the instructions on the manufacturer’s label closely
• always wear protective clothing
• always minimise the risk to desirable plants
• contact the supplier for further advice.
For further information and advice contact your local Biosecurity Plant Pest Contractor.
Visit our Waikato Regional Pest Management Strategy.
For more information on plant pests, please visit the Weedbusters website.
'What makes a pest a pest? - A guide to Waikatos pest management future' . Order, pick up free from our offices or download.
'Plant me instead - Plants to use in place of common pest plants' free from our offices, pick up or order.
Download the National Pest Plant Accord.
Pick up or order 'Poisonous plants and fungi in New Zealand - A guide for parents, schools and child minders' for $15 from our offices.