Japanese knotweed

Japanese knotweed

If you spot Japanese knotweed in your garden, follow our expert advice to tackle its rampant spread.

A table displaying which months are best to sow, plant and harvest.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Time to act
Time to act

Do not Time to act in January

Do not Time to act in February

Do Time to act in March

Do Time to act in April

Do Time to act in May

Do Time to act in June

Do Time to act in July

Do Time to act in August

Do Time to act in September

Do Time to act in October

Do Time to act in November

Do not Time to act in December

Japanese knotweed, Fallopia japonica, was introduced to the UK by the Victorians as an ornamental plant. But because of its rampant growth, and the fact it aggressively over-runs anything in its path, it’s now an offence to plant this in the wild. It spreads by sprouting from thick, woody rhizomes, and can grow 1.2m in one season. Winter is the only time of year that offers a reprieve, but for the rest of the year it’s a plant that needs tough handling as soon as it appears.



This weed is especially rampant and can grow to 2.1m in just one season, overwhelming any garden plants in its way. It doesn’t colonise gardens by producing seeds, instead it sprouts from very small sections of rhizomes.

Find it on

all over the garden


Weaken the plant by cutting off the top growth every two to four weeks. Let the cut stems wither in the sun until dead before digging up and disposing of them. Do not add them to the compost heap. If you dig up any rhizomes, you must take them to a licensed waste site, as they are a ‘controlled waste’ under the Environment Protection Act 1990.



Use a total weedkiller For best results, cut away old stems in winter and spray the plant in late summer when the weed is flowering. You will need to re-apply in midsummer, then check in September and spray again if needed. Check again in spring. It can take 3 or 4 seasons to eradicate. Avoid spraying on a windy day and near other desirable plants.