HomesAndHedge guides

Invasive plants, weeds and tree disease: identify, judge, act

Some garden plants and tree diseases are far more serious than others. A few, such as Japanese knotweed and giant hogweed, carry legal and safety implications. This hub helps you identify what you are dealing with, judge how worried to be, tackle what you safely can, and find the right specialist when a job is beyond DIY.

Not every weed is a crisis, and not every leaf spot means a dying tree. But a handful of plants and tree diseases carry real consequences: Japanese knotweed can affect a mortgage and the law restricts spreading it, giant hogweed sap can burn skin, and ash dieback can make a tree unsafe.

Each guide below follows the same shape: how to identify it, how serious it is, how to deal with it where you safely can, and who to call when a specialist is needed. Where a figure is quoted, it links to a named source such as the RHS, gov.uk, Forest Research or the Property Care Association.

Japanese knotweed High: legal restrictions and a real impact on property and mortgages Giant hogweed High: a genuine skin-burn hazard and a listed invasive plant Himalayan balsam Moderate: a fast-spreading listed weed, but easily pulled and controllable Bindweed Low to moderate: harmless but persistent and smothering Ash dieback High for affected trees: progressive decline and a real safety risk Honey fungus High for woody plants: no chemical cure, spreads underground Bamboo Variable: clumping is low risk; uncontained running bamboo can cause real disputes Leylandii Low risk to property; high for neighbour disputes over height and light

Frequently asked questions

Which garden plants have legal implications in the UK?

Japanese knotweed, giant hogweed and Himalayan balsam are listed under Schedule 9 of the Wildlife and Countryside Act 1981, which makes it an offence to plant or cause them to grow in the wild. You can be liable for letting some invasive plants spread to neighbouring land. Always check current gov.uk guidance.

Do I have to remove an invasive plant from my own garden?

You are not generally required to remove an invasive plant from your own land, but gov.uk explains you must not allow certain invasive plants to spread into the wild or onto neighbouring property, and disposal is controlled waste. Knotweed in particular can affect property sales and mortgages.

Who do I call about a serious invasive plant or tree disease?

For Japanese knotweed and other invasive weeds, use a Property Care Association (PCA) Invasive Weed Control Group member. For tree disease and unsafe trees, use an Arboricultural Association (ARB Approved) tree surgeon. Both bodies vet members and require insurance.

Oliver Mackman

Editor, HomesAndHedge

Oliver leads HomesAndHedge's editorial coverage of home and garden problems. He researches and writes the plain-English explainers on pests, invasive plants, damp and mould, drainage and wildlife, drawing on guidance from bodies such as the Property Care Association, the RHS and the NHS, and is clear about when a job needs a qualified professional.

Last reviewed: 8 June 2026