The above paragraph was written in the early 2000s when I first started my Wayne's Word website. The old Science Building has been torn down and replaced by a new Science Bldg. near the Edwin & Frances Hunter Arboretum where the fascinating Wigandia urens still survives.

Several species of Wigandia are native to Mexico, Central and South America. They are easily recognized along roadsides, with their very large leaves and glistening hairs (trichomes). They belong to the waterleaf family (Hydrophyllaceae) along with several genera of native California wildflowers, including Phacelia and Turricula. [Note: Members of the Hydrophyllaceae have now been placed in the closely-related borage family (Boraginaceae).] The purplish or violet flowers are produced in coiled (scorpioid) clusters and contain five petals which are fused into a bell-shaped or rotate corolla. The attractive bell-shaped corollas fall from the inflorescences intact, with five stamens inserted between the lobes. Wigandias can be rather invasive and need plenty of room. They spread by underground shoots that can literally break through hard, compact ground and asphalt. In the Life Sciences area, it appears to be spreading vegetatively by underground shoots (adventitious stems) and not by germinated seedlings. Wigandia urens is also established in the Palomar College Arboretum.

Dense, glistening trichomes adorn the inflorescence of Wigandia urens. The flowers are produced in coiled (scorpioid) cymes typical of the waterleaf & borage families; however, cladistical DNA evidence suggests this species is best placed in the subfamily Hydrophylloideae within the Boraginaceae.

Like our California phacelias and turriculas, the stiff hairs (trichomes) of wigandias can be irritating to sensitive skin. It is best not to handle wigandia plants without gloves. In fact, they are sometimes called "mala mujer" in Mexico; however, they are not nearly as painful or "bad" as the "mala mujeres" of the euphorbia family (Euphorbiaceae), including species of Cnidoscolus. [See photos of the true mala mujer below.] Like prickly pear and cholla cacti, the general rule of "look but don't touch" also applies to the hairy stems of wigandia. As long as wigandias are pruned back and viewed from a distance, they pose no serious threat to people. They are truly remarkable shrubs with foliage reminiscent of the rain-soaked New World tropics.

The undisputed "mala mujer" of Baja California, southern Arizona and mainland Mexico is Cnidoscolus angustidens, a member of the large and diverse euphorbia family (Euphorbiaceae). This species is a herbaceous plant with broad, palmately-lobed leaves. The stems and leaves are covered with stinging trichomes that readily penetrate leather gloves and discourage the most avid plant collector. Species in the related genus Tragia inject a painful crystal of calcium oxalate into the skin. Like nettles of the genus Urtica (Urticaceae), the trichomes of mala mujer are sharp, silicified epidermal cells with a bulbous base embedded in a stalk (pedestal) of smaller epidermal cells.

The trichomes of true nettles in the genera Urtica and Urera inject your skin with several stinging chemicals, including histamine, acetylcholine and 5-hydroxytryptamine. Some tropical nettles can be absolutely excruciating and cause numbness that may persist for weeks. There are reports of the incapacitation and death of horses from the Australian bush nettle Dendrocnide moroides. In general, the Australian bush and tree nettles of the genus Dendrocnide appear to be considerably more potent than the herbaceous North American nettles (Urtica and Urera). The chemical mechanism responsible for the extreme pain from contact with these tree nettles is apparently different from North American nettles. There are unconfirmed reports of human fatalities from a nettle called "devil-leaf" (Laportea or Dendrocnide) in Papua, New Guinea.

The stinging hair of the common North American nettle (Urtica dioica) is actually a sharp-pointed cell called a trichome. This nucleated cell is embedded in a pedestal-like base composed of smaller epidermal cells. The slender shaft of the trichome is composed of silica, and the rounded apex breaks off with the slightest touch creating a sharp, beveled tip similar to a hypodermic needle. The hollow trichome readily penetrates the skin and toxin from the enlarged, bulbous base is injected into the skin tissue. The stinging toxin from this species of nettle is a combination of chemicals, including histamine, acetylcholine and 5-hydroxytryptamine.

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