Blue Porterweed Groundcover Facts
Blue porterweed plants (Stachytarpheta jamaicensis) are native to south Florida, though they have since ranged throughout most of the state. Since they are only hardy to USDA zone 9b, they have not travelled farther north. Blue porterweed is often confused with Stachytarpheta urticifolia, a non-native cousin that grows more aggressively and should not be planted. It also grows taller, as high as 5 feet (1.5 m.), and woodier, which makes it less effective as a groundcover. Blue porterweed, on the other hand, tends to reach 1 to 3 feet (31-91 cm.) in height and width. It grows quickly and spreads out as it grows, making for an excellent groundcover. It is also extremely attractive to pollinators. It produces small, blue to purple flowers. Each individual flower stays open for only one day, but the plant produces such a large number of them that they are very showy and attract plenty of butterflies.
How to Grow Blue Porterweed for Ground Coverage
Blue porterweed plants grow best in full sun to partial shade. When they are first planted, they need moist soil but, once established, they can handle drought quite well. They can tolerate salty conditions too. If you’re planting them as groundcover, space the plants out by 2.5 to 3 feet (76-91 cm.). As they grow, they will spread out and create an attractive continuous bed of flowering shrub. Cut the shrubs back vigorously in late spring to encourage new summer growth. Throughout the year, you can prune them lightly to maintain an even height and attractive shape.
