Giant rhubarb (Gunnera tinctoria) removal
Not sure how to deal with Giant rhubarb? We’re here to help with advice and provide a complete treatment & removal package
What is Gunnera tinctoria?
Gunnera or Giant rhubarb is a large ‘clump-forming’ plant that likes damp conditions such as waterways, ponds and boggy areas. It is grown as an ornamental plant in gardens. Each plant is likely to mature to about two metres wide and 1.5 metres high.
It has been classed as an invasive species and is listed in Schedule 9 of the Wildlife and Countryside Act. While it’s not illegal to grow it in your garden, it is against the law to allow it to spread to other areas, particularly areas of natural beauty and the countryside.
What does it look like?
The plants usually have large, fan-like leaves with ragged edges. As they reach maturity, the stalks turn red or purple, which is where they get the association with rhubarb from. The leaves usually have fine, prickly hairs underneath and the stems also may have these.
During the late spring and summer, the plant forms colourful reddish panicles or cones of flowers which turn into berries later in the year and then become seeds in the autumn. These cones can grow to about a metre in length and contain thousands of seeds.
What damage is caused by Gunnera?
There are two distinct ways that an invasive plant like Gunnera can cause damage to the environment:
The first one involves what is going on beneath the ground. Gunnera doesn’t have a ‘traditional’ root system but rhizomes which are kind of creeping root stalks that spread underground. These allow plants in a particular area to spread and overtake the local ecosystem. When Gunnera dies back in winter, it often leaves bare soil that is left open to erosion. For areas like riverbanks, this can cause a significant impact on local flora and fauna.
The second issue with Gunnera is its seeds. The panicles produce small black seeds in their thousands, and these can be picked up by birds and other animals and dispersed on the wind. There can be as many as 80,000 to 250,000 of these seeds and depending on where they land, if the conditions are favourable, they are likely to grow and create more plants.
While Gunnera is less likely to cause structural damage compared to a similar rhizome plant like Japanese knotweed, it does present a real danger to local ecosystems if not spotted in time and removed. It can quickly dwarf local fauna and cause issues such as erosion.
What are the legal implications?
It is not illegal to grow any variety of Gunnera in your garden and many people do – it’s even been shown off at RHS flower shows. Gunnera tinctoria is however classed as an invasive species under the Wildlife and Countryside Act 1981, but the primary focus is on preventing the plant from spreading into the wild. That means you must prevent dispersal by;
- removing the berries or flowers before they start to develop seeds.
- Not discarding any viable plant material (via your council collection for example).
- Not transporting soil that may have viable propagules (seeds, rhizome).
Use our extensive guide to identify Gunnera
What does Gunnera look like?
Prevent costly damage to your property
How to get rid of Gunnera?
There are several DIY methods that you can use to control Gunnera but it’s unlikely that these will fully remove it.
First of all, if the plant is healthy and producing flowers, you must make sure that you reduce the risk of the dispersal of the seeds around late summer and autumn.
Gunnera can be cut back completely, and the stump treated with herbicide, but this is unlikely to reach down into the more well-established rhizomes. While these rhizomes can be near the surface, others may be up to a metre deep. They are big structures in established clumps, up to a couple of metres in length. That can make them difficult to excavate with simple gardening tools.
In addition to this, Gunnera tends to set up home in wet, boggy conditions which can make successful removal a lot more difficult if you don’t have the right equipment.
To fully remove Gunnera from your property or land, you need to combine an effective herbicidal treatment injected into the root system followed by excavation. Digging down more than a metre below the soil requires specialist equipment, which is why hiring a professional team is usually the best option. They’ll also set up a monitoring process once the work is complete to ensure that the infestation does not return, and you can be confident it has been fully removed.
With large clumps of Gunnera growing on potential construction sites, the usual method is to dig down to a metre and remove all signs of the rhizomes. The excavated Gunnera plant and its rhizomes then need to be disposed of properly at a licenced landfill site.
With any Gunnera growth, it is important not only to recognise where the initial problem is, but whether the infestation has spread beyond to other areas. Simply treating one area while the plant is thriving somewhere else won’t solve the problem.
With 25 years’ experience in the industry, Environet is the UK’s leading invasive plant removal company. During this time, we’ve been dealing with some of the UK’s most common non-native invasive plants including Japanese knotweed, Bamboo, Giant hogweed and, of course, Gunnera tinctoria.
If you require a specialist team that provides consulting as well as treatment solutions, we’re here to help.
We’ve worked with homeowners as well as local councils, construction and development businesses, farmers and conservation organisations over the years, operating right across Britain. If you want to find out more, contact our friendly team today.
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