Scientific Name: Impatiens capensis
Common Name: Jewelweed
(Information for this species page was gathered in part by Ms. Katie Kirstein for Biology 220W in Spring 2009 at Penn State New Kensington)
Appearance and Habitat
Jewelweed (Impatiens capensis) is a common, native, annual plant found abundantly in woodlands, ditches, stream sides, and in almost any site with sufficiently moist soil. It is endemic throughout North America in all but the most arid western and southwestern states. Jewelweed reaches heights of two to five feet and has large (3 ½ to 5 inches long), bluish-green, oval leaves that have coarsely toothed margins. Jewelweed flowers in mid-summer through the early fall. The pollinator flowers (see discussion below) form in the axils of the upper leaves in clusters of one to three. Each of these flowers is funnel shaped, orange, and about an inch long with distinctive, three lobed corollas.
Meaning of the Name
The origin of the name “jewelweed” has been explained in three different ways:
- The clear, silvery appearance of the leaves when they are submerged in water.
- The tendency of dew or rain to bead up on the leaves and sparkle in the sun.
- The jewel-like, showy nature of bright orange flowers.
Flowers and Pollination
Jewelweed actually has two types of flowers that form in the axils of the upper leaves. The very visible, orange flowers previously mentioned are readily pollinated by a wide variety of organisms (including hummingbirds, butterflies, bees, wasps, and flies) while much smaller, less conspicuous, green flowers ('closed flowers') never open for outside pollination. These closed flowers (visible in the axils of the top leaves at the right) self-pollinate and produce genetic clones of the parental plant. Jewelweed, then, utilizes both sexual and asexual reproductive strategies. The insect pollinated flowers increase in numbers with increasing light exposure (and, thus, increased rates of photosynthesis) and with increased availability of soil nutrients. The higher physiological cost of these flowers (especially the cost of nectar production) must then be environmentally payable for the plant to utilize the more evolutionary favorable sexual mode of reproduction.
Seeds produced in insect pollinated flowers can be forcefully ejected up to two meters away from the parental plant. Physical disturbance of the seed pods such as by the touch of a passing animal can stimulate the sudden ejection of the seeds. This feature allows the genetically recombined seeds to be transported away from the growth zone of the parental plant and, thus, possibly be placed in an environment that is slightly different from that of the parent. This feature is also the source of two common names for jewelweed: “touch-me-nots” and “poppers.”
The self-pollinated flowers set their cloned seeds in closed seed pods that are not capable of this ejection behavior. These seeds, instead, simply ripen and drop to the soil immediately beneath the parental plant. Thus, the precisely replicated genotypic seeds of the successful parental plant are deposited directly back into the same environment that favored the growth and success of the parent.
The leaves and stems of jewelweed contain fluids that are rich in the chemical “lawsone.” Lawsone has anti-inflammatory and antifungal properties that can ease the irritation of a number of types of dermatitis (including reactions to poison ivy, stinging nettle, and insect bites) and has also been used to help treat human fungal infections like athlete’s foot. The chemical name of lawsone is hennotannic acid. This orange-red dye can be extracted from the leaves and is used as a hair and skin coloring agent ("henna").
Caterpillars of many types of moths have been observed feeding on the leaves of jewelweed. White-tailed deer also eat the leaves. Jewelweed seeds are consumed by a number of species of birds (including ruffed grouse, Chinese pheasant, and bobwhite quail) and rodents (including white-footed mice).