Unlike its evil cousin, good knotweed is a garden gem

Erin Schanen


Some plants have a way of escaping notice. That is, until they don’t, and suddenly they are everywhere.

This has happened to me on multiple occasions, initially with Amsonia, a plant that I first noticed in a Brown Deer garden and thought I had discovered something uncommon only to then find that it is widely planted in our area. That “discovery” led to a bit of an obsession with Amsonias.

The plant family that has recently caught my eye is Persicaria, also known as knotweed. For years, I’d been under the impression that Persicaria was a thug and that its beauty could be a siren song to a life of gardening regret when it ran out of bounds and kept on running. Then I learned what I’d been missing out on.

There are “bad” knotweeds. So bad that they are borderline evil, if we allow ourselves to label a plant in such a way, and I’ve been traumatized by bad plants often enough that I absolutely do. But the plants that get bunched together as knotweeds suffer the fate of a few bad actors reflecting poorly on the whole group.

The confusion, as is often the way, involves that common name. Japanese knotweed (Fallopia japonica), the wretched, house foundation-destroying invasive species you’ve probably seen (it looks a bit like bamboo) and not realized its intent to take over the world, is much different from Persicaria amplexicaulis ‘Firetail,’ even though they are both commonly known as knotweed and are cousins in the Polygonaceae, or buckwheat, family.

‘Firetail’ and other cultivated Persicaria (which sometimes go by the common name mountain fleece, undoubtedly appeasing the knotweed-adverse) can be wonderful garden plants. I planted ‘Golden Arrow,’ a variety with chartreuse foliage and long, bright fuchsia flowers held vertically on skinny stems, last year to brighten up a part shade spot. They can stretch from full sun to part shade, but consistently moist (even wet) soil is a non-negotiable requirement for most.

At about 3 to 4 feet tall and wide ‘Golden Arrow,’ ‘Firetail’ and many other varieties, including a softer colored Persicaria bistorta ‘Superba,’ create a nice clump, with vertical structure and long blooms times that can help a garden transition through the season. This is not a plant that will be easily shoehorned into a crowded garden. Rather, you should just plan for them to need a bit of room to fill out, and you’ll be happy you did.

Other lower-growing Persicaria that function as ground covers and are grown mostly for their beautiful leaves are to be approached with a bit of caution. They can get quite rambunctious, although in our area they are on the cusp of hardiness so they may be naturally kept in check.

The worst part about some of these “good” Persicaria is that they can be difficult to find. I imagine garden center employees get tired of explaining the difference between good knotweeds and bad knotweeds.

 I keep hunting them down online. I’ve missed out on a lot of good Persicaria growing years, and I don’t intend to miss out on more.


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Ozaukee Press

Wisconsin’s largest paid circulation community weekly newspaper. Serving Port Washington, Saukville, Grafton, Fredonia, Belgium, as well as Ozaukee County government. Locally owned and printed in Port Washington, Wisconsin.

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