With pure, dainty petals and heart-shaped leaves, you could be forgiven for thinking Japanese knotweed wasn’t the invasive pest it is. Thankfully, its flowers make it easy to identify. So, what do they look like?
Japanese knotweed flowers are tiny, five-pointed rounded stars usually white or cream in colour. They are so small they form part of a cluster which grow at the end of the stem. This cluster is long and thin and looks a little like a spike. You can usually spot Japanese knotweed flowers against the plant’s bright green leaves.
Long thin clusters of Japanese knotweed flowers
Flowers look like tiny five pointed, rounded stars
When does Japanese knotweed flower?
Japanese knotweed blooms from the end of August to the beginning of September in the UK. As a perennial, it will bloom year after year unless it is treated.
Did you know, the best time to treat Japanese knotweed is when it’s in full bloom? The weed “drinks” herbicides far better when there is more surface area to “swallow” the spray.
Plants mistaken for Japanese knotweed
When it flowers, Japanese knotweed is mistaken for a few other plants. Here are the most common:
- Bindweed - often confused for Japanese knotweed because its flowers are white. However, bindweed flowers are trumpet-shaped and large.
- Houttuynia - houttuyania cordata also has bold white petals, but also sports a central yellow spike. What's more, Japanese knotweed has no distinctive smell, whilst houttuynia smells like oranges!
- Dogwood - produces white flower clusters in the summer, just as Japanese knotweed does. However, dogwood clusters are dome-shaped and the petals have sharper points!
Japanese knotweed stems full of flowers and seed heads
Large infestation of Japanese knotweed in bloom
Send us a photo
Not sure if the bloomin’ pest in your garden is Japanese knotweed? Send us a photo via our contact form! We’ll identify the suspect plant for free and chat about your options.
