Plant Porterweeds to Attract Butterflies and Hummingbirds
A novel flower for the butterfly garden
Stachytarpheta is a genus of more than 200 tropical annuals and perennials mostly native to Australia, the Caribbean and Central and South America. The genus name derives from Greek for “thick flower spike.” In the 1700s, British explorers in the coined the common name of porterweed after observing indigenous peoples of the West Indies using such plants to make a dark, foamy tea resembling porter ale.
While many people today still champion the culinary side of porterweeds, it’s their unique looks that captured my heart. Members of the verbena family (Verbenaceae), most porterweeds have serrated leaves held in pairs along curiously square stems (a trait shared with members of the closely related mint family, or Lamiaceae). Plants typically grow dense and bushy, though there are also species with low and sprawling or tall and upright habits.
Individual blossoms are small tubes flaring out into several lobes, like most verbenas. They emerge a few at a time along beautifully elongated spikes that gently bend and tumble about in a hundred different directions. Each blossom lasts just a day, but new ones appear daily throughout the year where I garden—South Florida—or until the first frost in colder climates.
Most porterweeds bloom in jewel-like tones of blue, purple, pink and red that are irresistible to butterflies and hummingbirds. A few species are velvety black and absolutely mesmerizing to behold, but those are about as easy to find as a winning lottery ticket.
Three species of porterweed are more available through retailers:
The most common also happens to be the shortest: Stachytarpheta jamaicensis, usually just called blue porterweed. It’s native to Jamaica, as the name implies, but it occurs throughout the Caribbean and South Florida, forming a low mass of glossy green leaves rarely more than a foot tall but spreading double that or wider. Flower spikes start out horizontal but then curve upward at their ends, each one dotted with pale lavender blue flowers.
Often confused with S. jamaicensis is nettle-leaf porterweed, Stachytarpheta cayennensis (syn. S. urticifolia), native from Mexico through South America. It can be distinguished by its darker indigo flowers and much more upright habit: Nettle-leaf porterweed can grow four to five feet tall in a single summer. My overall favorite porterweed cultivar is 'Midnight Moon', a dwarf form of S. cayennensis. It stays lower than three feet and covers itself with rich cobalt flowers accented with a white blotch. When paired with something of a lighter blue—floss flower (Ageratum houstonianum) or love-in-a-mist (Nigella damascena), for example—and underplanted with a chartreuse sweet potato vine (like Ipomoea batatas ‘Margarita’), it creates a ravishing picture.
Also native to Central and South America, coral porterweed (Stachytarpheta mutabilis) grows to similar dimensions as the nettle-leaf but has larger, more matte leaves. Though the wild species blooms in a brilliant orange pink, named selections offer a rainbow of colors: ‘Violacea’ (dark violet), ‘Durham’s Blue Eyes’ (lavender bicolor) and ‘Henlea’s Hummingbird Heaven’ (rich orchid purple). ‘Ruby Throat Red’ and ‘Mawmaw’s Magenta’ are aptly described by their names.
Growing porterweeds
In South Florida, porterweeds are top-shelf plants for pollinator gardens; their nectar-rich blooms are magnets for hundreds of butterflies, moths, skippers, bees and hummingbirds. Given the increased spotlight on bee- and butterfly-friendly gardening nationwide, porterweeds would make excellent warm-season additions for pollinator gardens in temperate zones. You can count on nonstop color (and, by proxy, nonstop butterflies) from early summer through the first frost.
And porterweed cultivation couldn’t be easier. These plants thrive in full sun or partial shade, suffer no major pests and love humid heat—making them a blessing to gardeners east of the Mississippi. Drought tolerant once established, they’re also not finicky about soil fertility or pH, although most bloom better with occasional feedings. New plants can be started from seeds or cuttings.
Related: Learn how to overwinter porterweeds and other tender perennials by taking cuttings in the fall: “Propagate Tender Perennials With This Trick”
Lastly, porterweeds are wonderfully versatile from a design perspective. Use them as unusual accent plants, as filler material en masse or for textural contrast near larger flowers like echinaceas, zinnias or daylilies. The blue and purple cultivars serve much like salvias, offering refreshing cool tones to the summer garden—with the perk of being far less brittle than most salvias.
If you can’t find porterweeds locally, try mail-order. Online retailers that carry species and cultivars include Kartuz Greenhouses; Almost Eden; and PlantVine. Sellers of seeds and plants can also be found on Etsy.
