Yellow Touch-Me-Not (Impatiens pallida)
Also called Pale Touch-Me-Not or Jewelweed. The name “Touch-Me-Not” comes from the explosive seedpods, which give no end of entertainment to children and any adults who are not beyond being entertained by natural amusements. The pods have parallel ribs connected by a thin membrane, and the membrane gets thinner and weaker as the pod ripens. At length the membrane can be ruptured by the slightest touch, and then the ribs instantly coil into springs, sending seeds flying in all directions.
These plants are close relatives of the garden Impatiens, which have similarly explosive seedpods. All Impatiens species have thick, juicy stems, and large colonies of them will form dense, even mounds.
We have two species of Touch-Me-Not in the area. Yellow Touch-Me-Not is more common in the north and at higher elevations; Orange or Spotted Touch-Me-Not (I. capensis) is more common in the south and at lower elevations. Pittsburgh is right where the ranges meet, so we get both, often in the same colony. The yellow species is more common here, but the orange is also very common, especially in lower areas.
The juice from the thick stems is supposed to be a good preventative for poison ivy if rubbed on the affected parts soon after exposure.
Gray describes the genus and the species:
IMPATIENS [Rivinius] L. BALSAM, JEWELWEED. Sepals apparently only 4; the anterior one notched at the apex (probably two combined); the posterior one (appearing anterior as the flower hangs on its stalk) largest, and forming a usually spurred sac. Petals 2, 2-lobed (each a pair united). Filaments appendaged with a scale on the inner side, the б scales connivent over the stigma; anthers introrse. Pod with evanescent partitions, and a thick axis bearing several anatropous seeds; valves 6, coiling elastically and projecting the seeds in dehiscence. — Leaves in ours ovate or oval, coarsely toothed, petioled. Flowers axillary or panicled, often of two sorts, viz., the larger ones which seldom ripen seeds; and very small ones which are fertilized early in the bud, their floral envelopes never expanding but forced off by the growing pod and carried upward on its apex. (Name from the sudden bursting of the pods when touched, whence also the popular appellation.)
I. pallida Nutt. (PALE TOUCH-ME-NOT.) F’lowers pale-yellow, sparingly dotted with brownish-red; sac dilated and very obtuse, broader than long, tipped with a short incurved spur. (I. aurea Muhl. ?) — Moist shady places and along rills, in rich soil, n. Me. and w. N. E., westw. and southw. July-Sept. — Larger and greener than the next [I. capensis], with larger flowers. A form with unspotted flowers occurs.