Blue Porterweed (Stachytarpheta cayennensis): Butterfly Magnet with Blue Spikes

Blue Porterweed: Continuous Bloom for Pollinators

Blue porterweed (Stachytarpheta cayennensis), also called blue rat's tail, verbena azul, or Cayenne snakeweed, is a tender perennial often grown as an annual. It produces endless spikes of small, vivid blue flowers from spring to frost, making it a top choice for butterfly gardens.

Botanical Profile

Native to the American tropics, this plant grows 3–4 feet tall with a sprawling habit. The flowers are borne on long, slender, rat-tail-like spikes that elongate continuously. Each tiny flower lasts a day, but new ones open daily. The foliage is rough, toothed, and slightly aromatic.

Garden Uses

• Butterfly and hummingbird magnet: One of the best nectar sources.
• Annual bedding: Mass in borders or containers for all-season color.
• Cut flowers: Spikes add vertical interest to arrangements.
• Self-seeds: May return in warm climates.

Grow in full sun, well-drained soil. Drought tolerant once established. Pinch young plants for bushiness. In zones 9–11, it's a perennial; elsewhere treat as annual. Can be invasive in tropical regions; deadhead to control spread.