Thesium: An Uncommon Perennial Forb Worth Knowing
If you’ve stumbled across the name thesium in your gardening adventures, you might be wondering what exactly this plant is all about. Thesium arvense, commonly known simply as thesium, is one of those plants that doesn’t make it onto most gardeners’ radar – and there are some pretty good reasons why.
What Exactly Is Thesium?
Thesium is a perennial forb, which is just a fancy way of saying it’s a non-woody plant that comes back year after year. Think of it as an herbaceous perennial that lacks any significant woody stems above ground. It’s the kind of plant that dies back to the ground each winter and pops up again in spring from its underground parts.
Where Does Thesium Come From?
Here’s where things get interesting – thesium isn’t actually native to North America. It’s an introduced species that has managed to establish itself in the wild and reproduce on its own. Currently, you’ll find it growing naturally in just two states: Montana and North Dakota. That’s a pretty limited range for a plant that’s been hanging around for a while!
Should You Plant Thesium in Your Garden?
This is where we need to have an honest conversation. While thesium isn’t classified as invasive or noxious (at least not that we know of), there are some compelling reasons why you might want to think twice before adding it to your garden:
- It’s not native, which means it won’t provide the same ecological benefits as indigenous plants
- There’s surprisingly little information available about its garden performance, growing requirements, or ornamental value
- Its limited natural distribution suggests it might be quite particular about growing conditions
The Case for Native Alternatives
Instead of gambling on thesium, why not consider some fantastic native forbs that will actually support your local ecosystem? Native plants are adapted to your local climate, require less maintenance once established, and provide food and habitat for native wildlife including pollinators.
Depending on your location, you might explore native wildflowers, prairie plants, or woodland forbs that are better documented, easier to grow, and more beneficial to the environment.
If You’re Still Curious About Thesium
The truth is, there’s a lot we don’t know about Thesium arvense. Information about its:
- Specific growing requirements
- Ornamental characteristics
- Garden performance
- Hardiness zones
- Propagation methods
- Wildlife benefits
…is pretty much a mystery. This makes it a challenging plant for the average gardener to work with successfully.
The Bottom Line
While thesium might spark curiosity as an unusual addition to a plant collection, the lack of available growing information and its non-native status make it a questionable choice for most gardens. Your gardening efforts are probably better invested in well-documented native plants that will thrive in your conditions and support local wildlife.
If you’re drawn to uncommon plants, consider researching rare or underutilized native species in your area instead. You’ll likely find much more rewarding options that come with the added benefit of supporting your local ecosystem.
