By RICK BORCHELT
It’s enough to make you believe in alchemy.
Pluck a leaf of jewelweed and hold it underwater: It becomes a shiny, shimmering silver coin. Or watch rain drops bead up onto jewelweed leaves; each drop could just as easily be mercury spilled from a thermometer.
And as we’ll see, it’s a beauty that is literally skin deep — and then some.
Jewelweed (Impatiens capensis or Impatiens pallida, depending on the flower color) goes by a host of other common names, including orange balsam (capensis) and touch-me-not. Around our suburbs, orange jewelweed is a common wetland plant that grows in practically any wet ditch, moist meadow or lakeside, and July finds it at the peak of its bloom. The flowers are a bright orange with deeper orange or red spots; they dangle like earrings from thin stalks under the leaves. Each flower has a long, curved spur at the end of which offers a nectar reward for the bees, butterflies and especially hummingbirds that pollinate the plant.
Jewelweed chooses its pollinators carefully. In order to keep from being self-fertilized (which reduces genetic diversity), the male parts of the flower mature first, dispense their pollen and wither away before the female parts of the same flower mature, guaranteeing another pollen donor will fertilize the flower’s ovaries.
Sometimes, though, even the best-laid pollinator plans go awry for jewelweeds.
If the plant ends up in shade that is too deep, or the water source for its wetland dries up in a drought year, jewelweed may skip the showy flowers altogether. Or the tops of the plant with all the flowers could end up as deer breakfast. In these extreme cases, jewelweed can go it alone.
Jewelweed has a second kind of flower that nestles next to the stem in the axils of the leaves and looks like a small, tightly clustered flower bud. This flower never opens – botanists call this type of flower cleistogamous, which roughly translates as closed marriage. The jewelweed pollinates itself inside the closed flower, not requiring any pollen from other flowers to set fruit or visits from any pollinators to make it fertile.
To be sure, cleistogamy is not the ideal circumstance: Pollination from other flowers and especially from flowers of other plants makes for more robust seed crops and bigger, healthier plants the next summer. But it will do in a pinch to see that particular patch of jewelweed through hard times. And jewelweed always has a few cleistogamous flowers even on normally flowering plants —just in case.
The jeweled tones of jewelweed leaves, by contrast, are a function of pure physics. Both sides of the leaf are covered with tiny hairs that trap air and repel water. Hold the leaf under water, and the trapped air produces a shining silver surface — a mystery that begs to be shared with children at your local streamside. The same thing happens when dew or raindrops fall on leaves in the field, with the water beading up into reflective silver disco balls.
Jewelweed has yet another surprise waiting for those of us who study the folklore of medicinal plants. The plant’s hollow, succulent stems hold a lot of viscous, clear sap reminiscent of aloe vera, that sovereign solution for kitchen burns and insect bites. In the case of jewelweed, the mucilaginous sap contains both a detergent compound, saponin, and an anti-inflammatory compound, lawsone (the same compound that gives henna its red color).
Together, they make a powerful antidote to poison ivy rash — the detergent dissolves urushiol, the sticky ivy resin that causes the allergic reaction, and lawsone soothes the inflammation. A variation on folk rhymes by the late poet Valerie Worth describes this nicely:
Jewelweed, starve ivy’s greed / Touch-me-not, stay ivy’s rot / Orange balsam, stop ivy’s poison.
Balsam is an old apothecary term for something that calms or soothes wounds. But where did the touch-me-not common name come from?
The last of jewelweed’s mysteries is exposed when you touch the plump, ripe seed pod: It literally explodes in your hand, catapulting seeds up to six feet away. The pressure of your touch breaks the tension holding the walls of the seed pod intact, and the individual wall segments rapidly snap back like tiny rubber bands, flinging the seeds inside away from the parent plant. As a crowning ecological touch, jewelweed seeds float and can drift far downstream or across the lake to new habitats.
In most of the Mid-Atlantic, we typically see orange, or spotted, jewelweed (capensis). The flower ranges from light orange to dark-reddish orange, but always with darker spots across the lip of the flower. Yellow, or pallid, jewelweed (pallida) is less common and seems to do better than orange jewelweed in drier conditions farther from standing water or damp soil.
Under ideal conditions, both jewelweeds grow into lush, full plants as much as five feet tall and just as wide if they aren’t crowded. Flowers begin to appear in June and continue until early autumn.
Jewelweeds do surprisingly well in the garden, too, in normal soil with moderate moisture. If they get too rambunctious tossing their seeds around and start to crowd other plants in your garden, the plants are shallow-rooted and easy to pull up. But be sure to share some of the stalks with your ivy-plagued neighbors.
Have questions for Rick about the world of nature in and around the Maryland suburbs, or suggestions for future columns? Drop him a note by clicking here or emailing rborchelt@gmail.com (rborchelt@ gmail.com).
