Invasive Plant Species Identification
Common Invasive and Non-Native UK Plants
Bamboo is perhaps one of the most popular plants in the UK that is actually invasive if not planted correctly. As some types of bamboo aren’t at risk of becoming invasive, it’s incredibly hard without expert help and excavation to fully understand the type of bamboo that is growing.
How to spot:
- Bamboo grows in groups, with individual stems (called culms) forming the noticeable part of the plant.
- Some bamboos have leaves, others may have flowers.
- Bamboo is split into two types, running and clumping, which refer to the root system.
- Often, garden centres will only tell you the colour or description of the bamboo rather than the root type, making it harder to identify as potentially invasive or not.
Himalayan Balsam Identification
Himalayan Balsam (Impatiens glandulifera) is a highly invasive species that grows rapidly, even in low light conditions, making it hard to contain. It also has explosive seed pods that can distribute seeds up to six metres from the original plant.
How to spot
- Individual plants can reach up to 3m in height.
- It has serrated leaves with distinct edges.
- The stems are green, until the plant begins to die back, at which point they turn red.
- Each flower has a hooded appearance, with white, pink and purple flowers, and these appear in the summer months.
- Each seed pod is small initially, but when touched will explode and spread very far.
Himalayan balsam prefers riverbanks and will grow in great swathes, taking over quickly in the summer months.
Giant Hogweed Identification
Often mistaken for elderflower or common hogweed, giant hogweed (Heracleum Mantegazzianum) is noticeable by its long stems that are thick and hollow, as well as its large white flowers.
How to spot:
- It’s up to five metres in height.
- Each head is up to 80cm in diameter with delicate white flowers.
- Deeply lobed and spiked tip leaves, which can grow up to a metre and a half wide.
- Each stem is hairy, with purple splotches and a thick circle of hair at the base of the stalk.
- It has dry, flattened oval seeds that spread quickly and are numerous.
If you think you may have seen giant hogweed, stay way away from it unless you have the correct PPE, as the sap can cause serious burns that last for many years.
Ragwort is controlled around areas that are used for livestock and foraging due to its toxicity, especially to horses.
Ragwort is an interesting one, as while it is not inherently invasive or non-native (some varieties are invasive and/or non-native), the damage it does to livestock is harm worth noting.
How to spot:
- Each stem can grow up to 90cm high.
- Large flat-topped clusters of yellow daisy-like flowers.
- Found in a variety of areas, including farmland and verges.
- Spreads through seeds.
While a beautiful plant to look at, some types of rhododendrons, if not properly cared for, are incredibly invasive and harmful to native species, as they grow over other plants, block out light and spread rapidly across areas.
The other negative to a rhododendron is the disease carrying ability it has, which is fatal to some of our native trees.
How to spot
- Rhododendron ponticum is a variety of rhododendron to be aware of and can be identified by the below:
- The plant is shrubby looking, with dark leaves that are glossy.
- Flowers appear in spring in a variety of colours, each at a cluster and often higher up the plant.
- Will grow up to eight metres tall if the space allows it.
Other Invasive Plant Species
While not as big a threat as the ones listed above, the following species are also invasive and cause issues to native wildflowers in the UK:
- Water primrose
- Floating pennywort
- American skunk cabbage
- Pitcher plant
- Duck potato
Schedule 9, part 2 of the Wildlife and Countryside Act of 1981 lists all invasive plants.