Tuberous Sweetpea: A European Charmer with a Spreading Habit
If you’ve ever wondered about that pretty pink-flowered vine popping up in fields and gardens across North America, you might be looking at tuberous sweetpea (Lathyrus tuberosus). This perennial climbing plant has quite the story – and quite the personality when it comes to making itself at home in new places.
What Exactly Is Tuberous Sweetpea?
Tuberous sweetpea is a non-native perennial herb that originally hails from Europe and western Asia. Don’t let the name fool you – while it’s called a sweetpea, it’s not the same as the annual climbing sweetpeas you might grow for cut flowers. This one’s got underground tubers (hence the name) and a much more independent spirit.
As a member of the pea family, it fixes nitrogen in the soil and produces those characteristic pea-like flowers in lovely shades of pink to purple. The plant grows as a climbing or trailing vine that can reach about 1.5 feet in height, though it spreads horizontally much more than it climbs.
Where You’ll Find It Growing
This European native has made itself quite comfortable across much of North America. You can find established populations in Manitoba, Ontario, Quebec, Connecticut, Illinois, Iowa, Kentucky, Maine, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, New Jersey, New York, Ohio, Pennsylvania, Tennessee, Vermont, Washington, West Virginia, and Wisconsin.
The Appeal (And the Caution)
There’s no denying that tuberous sweetpea has its charms. The purple flowers are genuinely attractive and bloom from mid-spring into summer, creating a nice splash of color. Pollinators seem to appreciate the blooms, and the plant’s ability to fix nitrogen actually improves soil quality.
However, here’s where things get interesting (and potentially problematic): this plant reproduces both by seed and by those underground tubers, and it’s quite good at spreading itself around. Once established, it tends to stick around and expand its territory with moderate enthusiasm.
Growing Conditions and Care
If you’re considering tuberous sweetpea, it’s pretty accommodating when it comes to growing conditions:
- Soil: Adaptable to coarse and medium-textured soils, pH range of 4.8-7.6
- Water: Medium moisture needs with medium drought tolerance
- Sun: Intermediate shade tolerance, so partial sun to full sun works
- Climate: Hardy to about -28°F (roughly USDA zones 4-8)
- Maintenance: Low fertility requirements, moderate growth rate
Planting and Propagation
Tuberous sweetpea can be grown from seed or tubers, though you might have trouble finding it commercially available. Seeds can be planted in spring, and the plant will establish itself from there. Keep in mind that seedling vigor is relatively low, so be patient with germination and early growth.
Once established, the plant spreads at a moderate rate through its underground tuber system. This can be great for quick ground cover, but less great if you’re trying to keep it contained.
Should You Plant It?
Here’s the honest truth: while tuberous sweetpea isn’t officially listed as invasive, its spreading nature and non-native status give many gardeners pause. If you love the look of climbing legumes with pretty flowers, you might want to consider some native alternatives first:
- Wild bergamot (Monarda fistulosa) for purple blooms
- American groundnut (Apios americana) for a native climbing legume
- Wild lupine (Lupinus perennis) for pea-family flowers
If you do decide to grow tuberous sweetpea, just be mindful of its spreading habit and keep an eye on it. Plant it where you don’t mind it naturalizing, and maybe avoid areas near wild spaces where it might wander off on its own adventures.
The Bottom Line
Tuberous sweetpea is one of those plants that sits in the gray area – not terrible, not perfect, but definitely persistent. It offers legitimate beauty and some ecological benefits, but it’s also a non-native that knows how to make itself comfortable. Whether you choose to invite it into your garden really depends on your personal philosophy about native plants and your tolerance for enthusiastic spreaders.
Whatever you decide, you’ll certainly have a conversation starter on your hands – and probably a plant that will outlast many of your more finicky garden inhabitants.
