Impatiens biflora Walter
Impatiens capensis, the orange jewelweed, common jewelweed, spotted jewelweed, or orange balsam, is an annual plant which is native to eastern North America (but considered invasive in the Pacific Northwest). It is common in bottomland soils, ditches, and along creeks, often growing side-by-side with its less common relative, yellow jewelweed (I. pallida).
Jewelweed is an herbaceous plant that grows 3 to 5 feet tall and blooms from late spring to early fall. The flowers are orange (sometimes blood orange or rarely yellow) with a three-lobed corolla; one of the calyx lobes is colored similarly to the corolla and forms a hooked conical spur at the back of the flower. Plants may also produce non-showy cleistogamous flowers, which do not require cross-pollination.
It often branches extensively. The round stems are glabrous (smooth) and succulent, and semi-translucent, with swollen or darkened nodes on some plants. The leaves are alternate and simple and have teeth on the margins. The seed pods have five valves which coil back rapidly to eject the seeds in a process called explosive dehiscence or ballistochory. This reaction is where the name 'touch-me-not' comes from; in mature seed pods, dehiscence can easily be triggered with a light touch.
Impatiens capensis was transported in the 19th and 20th centuries to England, France, the Netherlands, Poland, Sweden, Finland, and potentially other areas of northern and central Europe. These naturalized populations persist in the absence of any common cultivation by people. This jewelweed species is quite similar to Impatiens noli-tangere, an Impatiens species native to Europe and Asia, as well as the other North American Impatiens. No evidence exists of natural hybrids, although the habitats occupied by the two species are very similar.
Along with other species of jewelweed, the juice of the leaves and stems is a traditional Native American remedy for skin rashes, including poison ivy. The effectiveness of its use to prevent the development of a rash after short-term exposure to poison ivy has been supported by peer-reviewed study, and is likely due to the plant containing saponins. These studies also found that some individuals have a sensitivity to jewelweed which can cause a more severe rash.
The leaves appear to be silver or 'jeweled' when held underwater, which is possibly where the jewelweed name comes from. Another possible source of the name is the color and shape of the bright robin's egg-blue kernels of the green projectile seeds.
Nectar spurs are tubular elongations of petals and sepals of certain flowers that usually contain nectar. Flowers of Impatiens capensis have these nectar spurs. Nectar spurs are thought to have played a role in plant-pollinator coevolution. Curvature angles of nectar spurs of Impatiens capensis are variable. This angle varies from 0 degrees to 270 degrees.
The angle of the nectar spur is very important in the pollination of the flower and in determining the most efficient pollinator. Hummingbirds are major pollinators. They remove more pollen per visit from flowers with curved nectar spurs than with perpendicular nectar spurs. But hummingbirds are not the only pollinators of Impatiens capensis. Bees, especially bumblebees play an important role in pollination as well. Due to hummingbirds and bees, the pollination of Impatiens capensis is very high.
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