Plant species vary in their reproductive process. Some, such as Bamboo spread by underground roots systems (rhizomes), others spread via seeds. In this article we briefly explain how seeds can cause new infestations kilometres away. We also look at who’s responsible for stopping the spread.
nature
Seeds of invasive plants such as Himalayan balsam, Ragwort and Giant hogweed can all become airborne when released from their seed pods or seed heads, the wind carries them further afield. But they can also be picked up and carried by birds or animals (sticking to their bodies) or eaten by birds or animals and deposited in droppings further afield.
Humans and pets
But whilst it’s easy to blame mother nature for the spread of invasive plants, it’s us humans that are also to blame. Seeds can be picked up by us and our pets as we brush past plants, or by seeds that have dropped onto the ground. They easily stick to clothing, boots, equipment and vehicles, so if biosecurity precautions (such as cleaning clothing, footwear and equipment – for instance camping gear) are not taken hundreds of seeds can be transported further afield.
Vehicles
Even driving over seeds can cause them to stick to tyres and drop off elsewhere. This is especially evident on construction or development sites if works and transport vehicles are not cleaned down before leaving the site, or when moving from one site to another.
One of the worst species is Himalayan balsam as the seed heads explode on touch, so just brushing past them when they’re full and ripe can cause a cloud of seeds that, being very small and light will be carried on the wind several km away. Giant hogweed has large seed heads which, being located on the top of tall stems (over 2m high) can then be carried afar on the wind too.
| How It Spreads | How to Prevent It |
|---|---|
| Wind dispersal of seeds from seed heads/pods. | Avoid disturbing seed heads; remove plants before flowering or seeding. |
| Clinging to animal fur or feathers. | Fence off infested areas where possible; treat plants before seed set. |
| Eaten and dropped via animal/bird droppings. | Remove plants before seeding to prevent ingestion; control wildlife access if needed. |
| Sticking to clothing, boots, or pet fur. | Clean boots, clothes, pet fur and gear after walking through infested areas. |
| Tyres and machinery from construction/land work. | Clean all vehicles, tools and equipment before leaving the site. |
| Explosive seed ejection (e.g. Himalayan balsam). | Carefully remove before seeds mature; avoid brushing against mature plants. |
| Illegal dumping of garden waste. | Never place invasive plant waste in green bins or fly-tip; compliant disposal requires a license. Consult with a professional contractor. |
LEGAL OBLIGATIONS TO AVOID SPREAD
Who’s responsible?
The law states that it’s a legal offence for anyone to plant or allow to grow in the wild non-native plants listed on Schedule 9 of the Wildlife and Countryside Act 1981. Additionally Ragwort has its own Code of Practice. As it’s an illegal offence, governing bodies (such as councils and environmental agencies) can take legal action against the landowner.
It’s the council’s responsibility to implement agreements to control invasive plants (such as requesting residents with knotweed on their property to take out a knotweed management plan) and if need be enforce a penalty for non-compliance.
Most Councils enforce compliant disposal of illegal plants waste as it’s deemed ‘controlled waste’ and must not be taken to a landfill – as such must not be put into the council green bin. Most councils will contact a specialist contractor to control invasive plants on council owned land (such as parks, highways, streets and open spaces), and some councils will engage in public education to promote awareness. At Japanese Knotweed Ltd we provide training for council staff to help them identify knotweed and other invasive plants, and to be aware of the risks of toxic invasive plants such as Giant hogweed and hemlock.
If you’re responsible for managing property portfolios or land – it’s best to get it checked out and avoid legal implications.
We can help – arrange a survey.