Soft Butterfly Pea: A Tropical Ground Cover with Purple Charm
Looking for a low-maintenance ground cover that adds a splash of purple to your tropical garden? Meet the soft butterfly pea (Centrosema molle), a perennial herb that’s been making itself at home in warm climates around the Pacific. While it might not be a local native, this little legume has some interesting qualities that could make it worth considering for the right garden situation.
What Exactly Is Soft Butterfly Pea?
Centrosema molle is what botanists call a forb—essentially a non-woody perennial plant that dies back to ground level but returns year after year. Don’t let the fancy classification fool you, though. This is simply a spreading plant with pretty purple flowers that look like tiny butterflies, hence the charming common name.
As a member of the legume family, soft butterfly pea has the neat trick of fixing nitrogen in the soil through special bacteria in its roots. Think of it as a natural fertilizer factory that happens to produce lovely flowers.
Where Does It Come From?
Originally native to Puerto Rico and other parts of tropical America, soft butterfly pea has traveled far from home. Today, you’ll find it growing in Guam, Palau, and Puerto Rico, where it reproduces on its own without any help from gardeners.
Should You Grow Soft Butterfly Pea?
Here’s the thing about soft butterfly pea—it’s not native to most areas where it now grows, but it’s also not considered invasive or harmful. This puts it in that middle ground where the choice is really up to you and your gardening goals.
Reasons You Might Want It:
- Low-maintenance ground cover that spreads naturally
- Attractive purple butterfly-shaped flowers
- Improves soil by adding nitrogen
- Attracts pollinators like bees and butterflies
- Drought tolerant once established
- Perfect for naturalizing areas where you want something carefree
Reasons You Might Skip It:
- Not native to most areas where it’s grown
- Can spread aggressively in ideal conditions
- Native alternatives might better support local ecosystems
- Limited to warm climates (USDA zones 9-11)
Growing Soft Butterfly Pea Successfully
If you decide to give soft butterfly pea a try, you’ll find it refreshingly easy to grow. This plant practically thrives on neglect once it’s settled in.
Ideal Growing Conditions:
- Sunlight: Full sun to partial shade (though it flowers best with plenty of sun)
- Soil: Well-draining soil of almost any type—it’s not picky
- Water: Regular water to establish, then drought tolerant
- Climate: USDA hardiness zones 9-11 (tropical and subtropical areas)
Planting and Care Tips:
- Plant after the last frost in spring
- Space plants about 2-3 feet apart—they’ll fill in the gaps
- Water regularly the first season, then step back and let nature take over
- No need to fertilize—remember, it makes its own nitrogen
- Trim back in late winter if it gets too enthusiastic about spreading
- Watch for self-seeding in favorable conditions
Wildlife and Pollinator Benefits
One of the nicest things about soft butterfly pea is its appeal to pollinators. The purple flowers are magnets for bees and butterflies, providing them with nectar throughout the growing season. As a bonus, the nitrogen-fixing roots improve soil health, which benefits other plants in your garden too.
Consider Native Alternatives
While soft butterfly pea can be a useful garden plant, consider exploring native ground covers and legumes in your area first. Native plants have co-evolved with local wildlife and often provide superior ecological benefits. Check with your local native plant society or extension office for recommendations that might fill the same role in your landscape.
The Bottom Line
Soft butterfly pea is like that easygoing friend who adapts to any situation—pleasant to have around, low-maintenance, and occasionally quite charming with those purple blooms. Whether it’s right for your garden depends on your priorities and local growing conditions. If you’re in a warm climate and looking for a carefree ground cover that helps pollinators, it might just fit the bill. Just remember to keep an eye on its spreading habits and consider native options first.
