Stachytarpheta jamaicensis aka Light Blue Snakeweed

Stachytarpheta jamaicensis belongs to the verbena family. It is a perennial herb, which lives for years, or a small shrub. Names include blue porterweed, blue snakeweed, and Jamaica vervain. It is native to the southeastern United States and tropical America. It grows on beaches and roadsides in warm regions. Kew places it in the wet tropical biome. It has spread beyond its native range into Africa.

Plants form dense, round clumps with many branches. UF/IFAS gives a garden size of 4–8 feet [1.2–2.4 metres] tall and wide. It also notes plants reaching 4 feet [1.2 metres] before their stems droop. These spread about 6 feet [1.8 metres] across. Useful Tropical Plants describes a smaller herb that grows upright. It reaches 3.3 feet [1 metre]. Green stems have square sides and turn woody near the base. Dark green leaves grow in pairs, opposite or almost opposite. Each oval leaf is simple, with one blade. It has toothed edges and veins that branch. Leaves stay under two inches long and do not change color in fall. The plant keeps some leaves through the year.

Blue or pink flowers grow on long, thin spikes. The spikes rise from the tips of the stems. UF/IFAS records bloom in summer and fall. Butterflies visit the blooms, which adds value to wildlife gardens. The fruit draws little notice. Gardeners plant it in borders, hedges, and groups near buildings. Clipped plants keep a neat shape for months. Untrimmed stems may sag and leave gaps in the plant. Cutting back long, sparse stems helps new shoots fill gaps.

UF/IFAS advises a sunny site, though plants grow in part shade. They tolerate sand, loam, and clay, plus acid and alkaline soils. Water new plants while their roots take hold. Once rooted, plants cope well with drought. They still need water through long dry spells in summer. UF/IFAS lists USDA zones 10–11 and notes fast growth. It reports no serious pest or disease problems. Weed risk varies by region. UF/IFAS does not list the plant as invasive. Useful Tropical Plants reports large weed stands in Zanzibar. It also notes problems in crop fields.

People cook the leaves as greens, alone or with other vegetables. They use shoot tips for food and seasoning, too. They make tea from dried leaves or mix them with other tea. Useful Tropical Plants notes that people grow it in several tropical regions. They raise it for food and use as medicine. The source lists many folk remedies. These reports do not prove that the treatments work. It reports no known hazards, but this does not prove safety. People also make earrings from the flowers.