How to get rid of Japanese knotweed

How to get rid of Japanese knotweed

Japanese knotweed is a plant no one wants to find in their garden. Although it’s quite attractive (in Victorian times, it was planted as an ornamental), it’s also very invasive, spreading quickly in the garden and even growing through cracks in paving, where it can cause damage. The good news is, with care, it is possible to manage and even get rid of Japanese knotweed.

How to identify Japanese knotweed

Japanese knotweed (Fallopia japonica) is easy to identify once you know how it looks at different times of the year:

  • New shoots appear in spring, looking like red-purple asparagus spears.
  • The leaves are heart-shaped and tinged with red when they first appear, turning green as they mature. They grow alternately on the stems, giving the stems a very distinctive zigzag appearance, which is one of the easiest ways to identify the plant.
  • The plants produce tall, hollow bamboo-like canes topped with tassels of creamy white flowers in summer.
  • In fall, the leaves turn yellow and drop. The canes turn brown and die back but remain standing through winter.

How to identify Japanese knotweed?

Plants that look like Japanese knotweed

Several common plants can resemble Japanese knotweed at certain stages of their growth. If you’re concerned about a plant, check first to see whether it is one of these:

  • Bindweed (Convolvulus arvensis) has heart-shaped leaves, but they are smaller than those of Japanese knotweed. Bindweed doesn’t produce canes, instead climbing by twining itself around other plants. It produces large pink or white trumpet-shaped flowers in summer.
  • Himalayan honeysuckle (Leycesteria formosa) is a vigorous deciduous shrub with tall hollow canes and heart-shaped green leaves, similar to Japanese knotweed, but its white flowers are larger and are surrounded by burgundy-coloured bracts.
  • Russian vine (Fallopia baldschuanica) is a very vigorous twining climber. Its heart-shaped leaves and sprays of tiny white flowers in summer resemble those of Japanese knotweed, but it doesn’t produce canes.
  • Himalayan balsam (Impatiens glandulifera) is tall, like Japanese knotweed, with hollow stems but has longer, thinner leaves and sprays of pink flowers in summer. It self-seeds liberally if allowed to set seed.

How to get rid of Japanese knotweed

The most effective way of dealing with Japanese knotweed is to use the systemic weedkiller glyphosate. It typically takes several applications over 2-3 years to resolve the problem. As there is legislation relating to the management and control of Japanese knotweed on properties, if you find it in your garden it’s best to call in a professional company to remove it.

How to get rid of Japanese knotweed?

Remember! Whatever you do, don’t ever dispose of Japanese knotweed waste in your compost heap, in green waste bins, or in household waste – this is illegal, as it will enable the plant to spread.

If you need advice on the plants in your garden, why not visit our centre in Calgary? Our friendly staff are always happy to help.

You might also be interested in:

Here's how to make the most of your spring garden

When plants wake up during spring, it’s such an uplifting time of year and you’ll want to ensure you get the most from your spring plants until the early summer flowers take over.

Benefits of growing in grow bags 

Grow big in small spaces: tips for growing in grow bags! We will provide helpful tricks for growing a bountiful garden in limited space using grow bags.

6 spring plants to brighten up your pots

If your garden needs a dose of colour, come and see our fantastic range of spring plants. We have everything you need to brighten up pots, beds and window boxes this spring!

How to grow tomatoes

Enjoy the delicious taste of your own home-grown tomatoes this summer, sun-warmed and picked fresh from the plant! Find out more about how to sow and grow your own tomatoes.