Flora Fact: Mystery Stingers
Noseburn lies low, so you may not know what stung you.
By Dyanne Fry Cortez
Noseburn grows close to the ground and blends in well there, so gardeners and wildflower pickers often don’t notice it until they’re attacked by its stinging hairs. Even then, they may never see what “got” them.
The term “noseburn” refers to a group of related plants (genus Tragia) in the spurge family. At least six species are found in various Texas regions: Pineywoods, Hill Country, Rio Grande Valley and far West Texas. Though small in stature and unremarkable in appearance, these plants aren’t difficult to spot if you know what to look for.
Noseburn flowers don’t look like much. They don’t have petals, and although they are distant relatives of the poinsettia, they lack the colorful bracts that make their tame cousins so popular at holiday time. The nondescript blooms appear in small clusters, with male and female parts in separate flowers.
All noseburns have this in common: the entire plant — stem, leaves and fruit — is armed with stinging hairs. They’re small, but visible. Turn a leaf sideways to the light, and you’ll see little spikes protruding from both sides. In strong sunlight, the hairs seem to sparkle. That’s because each one is tipped with a tiny crystal of calcium oxalate.
A 1976 study at Texas A&M University took a close look at the stinging mechanism. Viewed with an electron microscope, each hair is seen to be a four-celled structure. Three support cells surround a tall central cell that rises above the leaf’s surface, with a crystal at the tip and a cavity down below that holds a drop of irritating fluid. The crystal works like a spear point: touch the plant and it pierces your skin. The fluid irritant comes right behind it, released by pressure on the bending hair.
Any brush with noseburn is likely to involve dozens of stinging hairs. You may find noseburn lurking where you kneel to pick a wildflower, or it may assault your toes and ankles as you stroll across a meadow. You may lie down on a grassy hillside to gaze at clouds and find yourself leaping up moments later, wondering if you’ve planted yourself on a fire ant mound.
In my encounters with noseburn, I’ve experienced a few seconds’ delay between contact and sting. If I’m moving fast, I may be several feet away from the source of trouble before I know I’ve been hit. Fortunately, the sting subsides after a few minutes and does no lasting harm.
Over time, I’ve come to regard the tricky Tragias as friends. They aren’t beautiful, but they’re survivors. They fly under the radar and know how to take care of themselves. Their stingers are marvels of engineering.
And they give me one more reason to remember that, while enjoying the Texas outdoors, it’s always best to watch where I step.
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