Increasingly rare, Florida stinging nettles (Cnidoscolus stimulosus (Michx.) Engelm. are a perennial herb covered with stinging hairs, and containing milky sap and tuberous roots. This Florida native is found throughout the state but prefers dry sandhills which also happen to be the preferred habitat of developers and their bulldozers.
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Stinging Nettles of Florida are known by a lot of common names, most often, "Tread Softly," an admonishment to be careful of where one walks. Cnidoscolus stimulosus, its scientific name (as in "stimulating") is an understatement. "Bull Nettle" is another commonly heard name implying the plants potency. "Florida Finger Rot" is an exaggerated comment on the impact of the stinging trichomes (pubescences). Meanwhile in the Carolinas this plant is often referred to as "Fly-fly," and we're not sure what the reference is in that colloquial name.
The Choctaw called this plant "hashtapola." Florida Crackers often referred to it as "spurge nettle" ("spurge" is from Old French espurge, in turn based on espurgier, and Latin expurgate, to cleanse or purify from impurity; the verb has been used in English since the 14th century). The English colonizers who landed in Florida called it "stinging nettle" (in use in English by 1525, although it was spelled "styngynge nettylles" and originally applied to European Urtica, then later to American plants).
Description
Erect plants are covered with stiff stinging hairs; palmately 3- to 5-lobed leaves, conspicuous tubular-based white flowers in a cluster terminating the stem; 3-parted bristly capsule with 3 mottled seeds. Blooming all year in Florida. Note the variety in the flower shapes among the colony of Cnidoscolus photographed here, occurring on an isolated sandhill in Debary, Florida.
Flowers
The flowers are unisexual (male and female in the same cluster), 1.5 cm (0.5 in) wide, with 5 white, petal-like structures (calyx lobes) and tubular base 1.5 cm (0.5 in) long; several arranged in forked clusters terminating in the stem.
Stems are erect to reclining, to 1 meter (3 ft) tall, but usually shorter, branched or unbranched and also containing stinging hairs.
Leaves are alternate, bright green to dark green, irregularly and deeply 3- to 5-palmately divided (like a hand), coarsely toothed, 8-30 cm (3-12 in) long and wide; leaf stalks (petioles) are usually long.
Toxicity
Irritant compounds that cause intense stinging and itching fill the long, stiff, hollow hairs on the stem, leaves, flowers, and fruits. Although not intensively studied, the injection mechanism may be similar to that in Urtica species like Heart-leaf Nettle: each hair ends in a blunt tip that breaks off, permitting injection of the poison into the skin. Often a rash (or tiny red bumps) appear after the burning sensation wears off (usually less than 30 minutes). In sensitive individuals, the rash or dull purplish discoloration may persist for several days.
In the more studied Urtica the irritant compounds are histamines and acetylcholines that cause reddening and intense itching. When the tip of the brittle, tubular hair is broken, pressure on the bulbous hair base injects the irritants into the skin. The usual reaction, reddening and intense itching, is usually of short duration, although sensitive individuals may experience swelling and burning.
If stung washing the infected area with an application of baking soda paste will soothe the stinging sensation in most people.
After the Austrian botanist Johann Baptist Emanuel Pohl (1782-1834) traveled and collected plants in Brazil, he returned home and published a book on his discoveries in 1827. That book, Plantarum Brasiliae Icones et Descriptiones (Descriptions and Drawings of Brazilian Plants), included one of his more stimulating finds, Cnidoscolus. Earlier, in 1813, André Michaux had named the southeastern United States species Jatropha stimulosus. It was not until 1845 that St. Louis physician George Englemann (1809-1884) and Harvard professor Asa Gray realized that the Michaux species belonged in Cnidoscolus. There are now approximately 75 species in this American genus with 4 in the United States.
Seeds and roots were studied in the 1960s and are indeed edible, but barely worth the effort to obtain them. In Murphee's 1965 Folk Medicine in Florida: Remedies Using Plants (Florida Anthropologist 18(3, pt. 1):175-185, Murphee describes how people in the Panhandle of Florida made a tea to "give a man courage" (a sex aid). Other scientific papers from that decade describe how in the Carolinas, milky sap of the root was mixed with Smilax laurifolia and steeped in whiskey or gin to increase male potency. So across the South this plant was once thought of as the viagra of its day.
The first American literary reference to Florida Stinging Nettles was when Procher wrote (the long-titled) Resources of the Southern Fields and Forests, Medical, Economical, and Agricultural. Being also a Medical Botany of the Confederate States; with Practical Information on the Useful Properties of the Trees, Plants, and Shrubs. (Steam-Power Press of Evans and Cogswell, Charleston, SC, 1863).
He said in part "It might be employed like the nettle (Urtica), as a counter-irritant in epilepsies, and disease requiring stimulating applications."
While cultivation is probably not a good idea, for my rather exotic and native-heavy Florida garden I collected seeds to start some Cnidoscolus plants. They produced well. However when I attempted digging up a plants tubers to transplant, it resulted in complete failure and death of the disturbed plants. Like most sandhill natives that cling to the dry, sandy soil, disturbing their roots can be fatal.
My cultivation advice: if you find a plant in the wild wait for its seeds to ripen then collect the seed, carefully wearing thick leather or rubber gloves that the nettles cannot penetrate.
The seed capsule is oval in outline, 3-parted, 1.5 cm (0.5 in) long, explosively dehiscing to release 3 seeds; seeds oval in outline, 6 mm (0.25 in) long, dark brown, mottled, with conspicuous swelling (caruncle at one end). The seed capsules are prominent in the images above and below.
The explosive release of the seeds usually happens on a hot summer day or when disturbed. The capsules are reminiscent of the exploding capsules of the Castor Bean plant (Ricinus communis), which produces many more seeds than Stinging nettles and is much more successful at throwing those seeds long distances.
On a very hot and very dry summer or fall day its something to behold when these plants start flinging their seeds, seemingly spontaneously, with explosive force.
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