Tread-softly and its look-alike cousin, bull-nettle (Cnidoscolus texanus (Müller Argoviensis) Small) are members of the Euphorbiaceae, the spurge family. The 75 or so species of Cnidoscolus are native to the Americas; four species are native to the US. Tread-softly ranges across the southeast from Virginia to Louisiana; bull-nettle ranges from Kansas south to Texas and east across Arkansas and Louisiana.

Tread-softly is a dry land plant found in scrub and sandhill habitats. Usually the leaves are deep green. The photographed plant is suffering from chlorosis which causes the yellow blotching. The sandy soil has insufficient nutrients to support chlorophyll in all the cells.

Tread-softly is monoecious; the white flower is staminate (male) and composed of a calyx (the sepals collectively) and stamens. The pistillate (female) flowers are green and tucked below the showier males. Butterflies, especially zebra longwings, frequent the male flowers. The female flower is followed by a three-part capsule. Quail and other birds are known to eat the seeds.

The shock and colorful terminology used when one encounters tread-softly are due to the fine trichomes (plant hairs) covering the leaves, stems, and capsules. Silica is laid down in the cell walls of the trichomes. In essence, the plant has grown hollow glass splinters. The lightest touch and the trichomes break off in the skin. That is just the beginning of the pain.

Like a miniature hypodermic, a gland at the base of the broken trichome pumps a soup of chemicals into the skin—5-hydroxytryptamine, and possibly acetylcholine, histamines and others, these have not yet been verified. Five-hydroxytryptamine, also known as serotonin, causes burning pain, gasping, and intense tingling.

A tiny dose causes pain for only an hour or so. But a good whack of tread-softly and the pain can last a day or longer. In large doses such as one would get with a scorpion sting, serotonin can bring on cramps, nausea, and vomiting. Tread-softly, then, is more advice than name.

(Compiled from: "Cnidoscolus", Hortus Third, Staff L.H. Bailey Hortorium, NY State College of Agriculture and Life Sciences, Cornell University, Macmillan, NY, 1976; "Urtica chamaedryoides Pursh: a Stinging Nettle, or Fireweed and Some Related Species", Nancy C. Coile, Botany Circular No. 34, Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Sept/Oct 1999; "Chemical contents of stinging trichomes of Cnidoscolus texanus", S.E. Lookadoo and A.J. Pollard, Journal of Chemical Ecology, Vol.17,No.9, Sept.1991; "Serotonin, a molecule of happiness", Claire Rosling, Molecule of the Month, April 2005, School of Chemistry, University of Bristol.)