How does knotweed spread?

Although knotweed has flowers, it primarily spreads via rhizomes. Rhizomes are basically subterranean root factories. Rhizomes are hyper-efficient vegetative reproductive organs that send a stem upward, but also send roots and shoots outward from underground nodes. These roots and shoots quickly create their own independent stems and systems. This allows the plant to multiply at warp speed. Because rhizomes are mostly underground, spread often goes unnoticed. Rhizomes are one of the most effective means of reproduction in nature. But wait, it gets worse.

First signs of knotweed

Knotweed rhizome spread

The tiniest piece of knotweed rhizome can grow into a new plant. This, my friends, is the secret to knotweed’s explosive growth. Little, itsy, bitsy, shreds of knotweed rhizomes being transported all over the place by watershed, wind, moving water, boots, lawnmowers, contaminated soil, wood chips, nursery plants, truck tires, snowplows, and much more. Seen knotweed on roadsides? That’s why, seen knotweed along streams and rivers? That’s why.

Knotweed at a garden center

Don’t bring knotweed home

The best defense is a good offense so always keep your eyes peeled for knotweed. Don’t bring it home. Scan potted plants, nurseries, building material, soil and compost yards, and any other spots where you might inadvertently bring it home. If you already have knotweed and are trying to eradicate it, dispose of it responsibly so you don’t screw over your neighbors.

rhizome ginger

More on rhizomes

Rhizomes aren’t all bad. Some more familiar plants reproduce via rhizome too. For example, bamboo, ferns, many grasses, and ginger have rhizomes. If you’ve ever bought fresh ginger at a grocery store, then you’ve seen (and probably eaten) a rhizome. On that note, knotweed rhizomes, young leaves, and other parts of the plant are consumed by some people. Not us. We prefer killing it and don’t recommend eating it.