I’m a plant that’s invasive beyond belief,
Able to grow through concrete, good grief!
I grow on stream banks and form dense stands,
I cause erosion to much of the land.
What am I?
This plant originates from Japan, with hollow, segmented stems that resemble bamboo. Can you guess what it is?
It’s Japanese knotweed (Fallopia japonica)! It flowers from July to September and produces seeds from October to November. It thrives in various environments, from moist soil to river cobble, and from full to partial sunlight. It can be found dominating rivers, creeks, roadside ditches, and beaches. Due to its extremely aggressive spreading habit and its devastating effects on infrastructure and the local ecosystem, Japanese knotweed is a high-priority species in the Sea to Sky region. It is abundant in certain portions of the region (i.e., in Squamish and south) but has not yet infested all potential habitats. The goal is to contain the spread of Japanese knotweed to ISMA 1, while eradicating it from ISMAs 2 and 3.
Japanese knotweed is part of the Squamish’s Most Wanted series.
Where am I?
I spy with my little eye… Japanese knotweed!
Can you find it?
Click through to find the answer!
Japanese knotweed can be easily identified by several distinctive features:
- Hollow, upright green stems with reddish-brown speckles. The stems resemble bamboo.
- Egg-shaped leaves that are 3-10cm long, and the veins on the underside of the leaves have blunt knobs.
- Flowers grow in small, plume-like, and branched clusters. The flower colour is typically a creamy white.
- An underground network of rhizomes. Fresh rhizomes are yellow or orange inside.
What are the different types of knotweed?
Four types of knotweeds are of concern in the Sea to Sky. Japanese knotweed, Bohemian knotweed, and Himalayan knotweed are all currently found in the Sea to Sky, while giant knotweed has (thankfully) not been found yet.
All four species are perennial, with their above-ground vegetation dying off in the winter, while the below-ground vegetation lies dormant. These species can be distinguished by their leaf shape and size. Check out the Knotweeds Species Profile Page to learn more about their differences.
Giant knotweed
Himalayan knotweed
Bohemian knotweed (carita, iNaturalist)
Why is Japanese knotweed such a concern in the Sea to Sky?
Japanese knotweed is an aggressive spreader with no natural predators in our area. It spreads by stem or root fragments. Even a small piece of Japanese knotweed (as little as 0.7 grams) can re-sprout into a new plant. As Japanese knotweed likes to grow near water, parts of the plant can also be transported by water flow.
Japanese knotweed disrupts food chains and threatens biodiversity by shading out other plant species, reducing available habitat, and increasing soil erosion along streambanks. This species also causes damage to infrastructure as it can grow through concrete, reduces sight lines along roads, and impedes access to waterbodies.
Please visit its species profile page to find out how to help.
I Spy… some prizes!
Guess the invasive species in our I Spy in the Sea to Sky weekly social media post, June through August, to enter our giveaway.
At the end of each month, one lucky commenter will win a native wildflower seed mix packet!
CONTEST RULES:
- To enter the contest, guess the common name of the invasive species by answering the poll on Instagram, or commenting on Facebook.
- One entry per person per post (hint: participation on each post increases your chances of winning, so be sure to keep an eye out for all I Spy posts).
- Anyone can play, but only Sea to Sky region residents can win.
- This month, entries will close at 11:59 PM PST on August 31st, 2025.
- Winners will be announced in the first week of August in an Instagram story AND contacted directly via their platform of entry.
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