Spring is a critical time for identifying and forming an effective plan against troublesome invasive plants in the U.K. In our handy article we will discuss key species to watch, how to identify these species, DIY control methods, and the benefits of professional help. As invasive plants exit winter dormancy, it is crucial to keep an eye on the area for new growth, and to be ready with a solid solution to battle these Alien species.
Common Offending Species
- Japanese Knotweed growth begins with red & purple asparagus-like shoots, with rapid growth climbing by up to 10cm per day. Mature shoots can develop rapidly, with inch thick shoots developing tall canes in a matter of days. Juvenile growth will emerge with pencil sized shoots, and may only reach 30-50cm in height. Infestations in the South of England will develop sooner than those in the North of England due to temperature differences, similarly with winter dormancy coming sooner in the North.
- Giant Hogweed emerges with large ground covering leaves, with the harmful cane emerging in mid-late spring. The ground cover is similar visually to Hemlock, Carrots and Wild Parsnips, with lacey leaf coverage generally around 10-30cm in height. It is important not to touch this plant to avoid harmful phototoxic sap burns than can last for many years.
- Bamboo shoots emerge through winter in preparation for spring. Once the temperatures stabilise, these shoots can extend seemingly overnight will tall proud canes covering the area. Once a plant is mature, the canes will spread wider and farther from the original planting location. Cutting back shoots can cause runner rhizomes to escape farther away from the original stand, until the plant finds a safe location to establish growth.
- Himalayan Balsam germinates early in March-April, with pink flowers emerging towards late May. More information can be found below in our article on the 'Pink Invader'.
DIY & What to Know
There are many tried and tested DIY solutions to keep your invasive plants under control. These methods will not fully kill the plant, but over time will reduce the rhizome energy storage and weaken the plant, reducing the ability to spread and grow. The key is consistency, rhizome systems can take up to a decade to show lasting effects from DIY methods.
For Himalayan Balsam, you can hand pull the growth in early spring to prevent the growth extending to seed production. This is sometimes referred to as Balsam Bashing, even strimming the ground can disable seed production to reduce the seed bank over the affected area.
Japanese Knotweed can be cut low to deny photosynthesis taking place, and new energy being stored. It is important to note that all parts of the plant are classified as controlled waste, and therefore cannot be disposed of in general waste or compost. It is also possible to dig the area to breakup the rhizome system, but it is important to not remove any soil or roots from the area. By leaving the fragments of the broken rhizome system, these small pieces can be controlled with herbicides in the years following a small manual excavation.
Bamboo can be controlled by cutting back shoots and growth, and injecting a stump killer herbicide into the cut shoots. For mature stands that have been in the ground around 10 years, this process can take up to 10 years, and even longer with ineffective treatments. It is important to consider a herbicide with a silica dissolving element, as the hardy shell of the rhizomes need to be broken down for proper absorption. It is important to wear PPE and act cautiously with herbicide chemicals. We recommend contacting a licensed pesticide expert.
DIY Treatment Risks:
- Regrowth will be consistent after the initial excavation or herbicide treatments. Consistency is key, and you will need to be active in the areas at the main points of growth, Spring and Autumn for up to 10 years. DIY Treatments are generally ineffective in the long term without consistency, and specialist guidance.
- Poor bio-security considerations will lead to contamination and spread over a larger area. Minuscule rhizomes as small as a finger nail can easily be tracked and spread. Rhizomes left on the surface are at risk of being disturbed by wildlife, wind and rain.
- Health Risks: Plants like Giant Hogweed can leave serious skin burns from phototoxic saps. We do NOT recommend treating this species without specialist advice and full personal protective equipment. Many herbicides are carcinogenic and can cause serious health issues if handled incorrectly.
- Legal Risks: Improper disposal of controlled material can lead to legal fines and Community Protection Notices being put in-place.
Property owners have a legal duty under the Wildlife & Countryside act of 1981 to prevent spread into the wilderness. Plants like Japanese Knotweed can cause property sale issues with mortgage retention and boundary disputes with neighbouring properties. It is important to understand the law surrounding Invasive Plants, early detection and action is crucial to mitigate the impact and risk.
Benefits of choosing a Specialist:
- Long term Guarantee Coverage with unlimited free call outs to treat all regrowth.
- Access to controlled Herbicides for commercial use by licensed Operatives.
- Compliance & Risk avoidance through specialist and experienced guidance.
- Tried & Tested specialist equipment and machinery, designed for precise tasks.
- Faster, more effective solutions for infestations of all sizes.
- Free consultations, survey reports, guidance & advice.
Herbicide Treatment Planning for 2026 Growing Season
Herbicide Treatments for this growing season will begin from early June for mature stands, and typically mid July for smaller less mature stands. Regrowth may not emerge fully until August-September, which can be treated in the second window between September and November. Late treatments are typically the most effective, as the plant binds to the chemical as the energy is sent downwards prior to entering winter dormancy. Some stands and locations will require Stem Injections to prevent contamination to waterways and surrounding shrubs or crops.
Get in touch with a specialist at Alien Plant Control today for free & helpful advice: