Touching these plants will cause, not great bodily harm, but instead will provide a startled response from the uninitiated who touches or brushes against the seed pod, for when ripe, they release their seeds explosively at the smallest touch. There are two species in the Eloise Butler Wildflower Garden - the Spotted Touch-me-not, Impatiens capensis Meerb. and the Pale Touch-me-not, Impatiens pallida Nutt. Use the links for more detail and more photos.
The Spotted is a deep yellow color with red-orange spots. Note that it has a little tail on the back of the the corolla spur that bends under then forward and upward - kind of like the curl of a pigs tail. The Pale (photo below) is a pale yellow with some red-orange spots, is larger, and its' tail just bends downward and maybe a little forward.
Both have 5 petals. In the Spotted, two are almost united forming the lower lip wheres in the Pale, the lower lip is of two separate petals. Uniquely, one of the three sepals in each species is colored the same as the petals and it forms the long tubular spur behind the petals. The leaves and stems look similar.
The flowers are dichogamous, that is, with the male and female parts maturing at different times, thus avoiding something nature does not like - self pollination. The male parts are ready first and the anthers are ready for pollen release for only a twenty-four hour period, then the anthers are dropped and the female stigma is exposed. The receptive phase then follows when the stigma can receive pollen but that phase is very short - average of four hours according to experiments that have run.
The cleistogamous flowers are found singly in the lower leaf axils and require only three weeks to mature. These are usually produced later in the season. These are only 1 to 2 mm in diameter. These flowers produce seed when, through stress or other climatic conditions, the regular open flowers are few or cannot be pollinated. Also, since the type of pollinator required for the open flowers, due to its deep nectar sac, is quite limited, and also since the plant is an annual, cleistogamous seed production insures that the species will re-seed.
Seeds are longer than wide, brown with lighter ridges and usually number 3 to 5 per pod. The cleistogamous flowers also form seed pods but contain fewer seeds. Hummingbirds and large bees are the prime pollinators. By inserting a hummingbird's long tongue into the curved nectar spur, the spur is pushed away with each lick of the tongue and then the spring-like action of the pedicel brings the flower back toward the bird causing the anthers or the stigma to contact the back portion of the birds bill, thus transferring pollen. [see Mobility of Impatiens capensis flowers: Effect on pollen deposition and hummingbird foraging by Hurlbert, Hosoi, Temeles and Ewald, Spring 1996 published in Oecologia.] Another article that covers in detail the research on the open and closed flower types in this species is Jewelweed's Sexual Skills, by Donald M. Walker, University of Wisconsin, in Natural History, Vol. 91 #5. and also papers in Evolution, Vols. 34, 38, 41.
Now to the fun part. The seed capsules are thin cylinders and usually no more than an inch long (photo below). When the capsule is ready, touching it with slight pressure will cause the plant material inside to suddenly form a twisted coil (below right) and split the capsule, (called 'dehiscing') dispersing the seeds to quite a distance. This happens when the capsule is still in the green state. If you gently pluck one and close your hand on it you can capture the seed and the coiled material. Children can be thrilled by this trick of nature. Touch-me-nots are annuals thus this process allows the plant to reseed itself and to spread. Unfortunately, that also makes them invasive (more below). For details on the mechanism that releases the seeds explosively, see this article (pdf)
Eloise Butler wrote the following comments about how Jewelweeds were viewed in her day: "Every inch of space on low, moist soil not held firmly by tufted meadow grasses and sedges is occupied by the Wild Balsam. [Note: “Wild Balsam” is derived from the Latin family name for the species, BALSAMINACEAE and in English as the Touch-me-not Family.]
The smooth, glossy stem has a translucent appearance, and its joints are swollen, affording another proof, of course, that rheumatism is induced by dampness! The leaves are thin and delicate. When dipped in water, their under-surfaces appear to gleam like quicksilver, an appearance due to tiny hairs that catch the water and enmesh air bubbles. The hairs keep the pores that are abundant on the under side of the leaves from being clogged with water. Some water beetles show the same phenomenon when they dive; but, in their case, the air bubbles supply them with the requisite oxygen during the period of immersion. Little girls are familiar with the plant as Jewelweed. By means of the curved nectar spur, they hook the flowers in their ears and are fine ladies, for the nonce, with gold ear-drops. The most common species of Balsam has flowers usually spotted with brown, of varying shades of orange and yellow, and sometimes pink or white. This is called Impatiens biflora [note: This was the name in her day - now I. capensis]. I pallida has larger, pale yellow, often unspotted flowers, with stouter spurs. The term Impatiens refers to the nature of the seed-vessel, the origin of another common name, touch-me-not. If you gently press the plump, ripe seed-pod between your thumb and forefinger you will be startled by its breaking up into writhing, worm-like pieces, and by the seeds snapping out several feet into space." Published Aug 20, 1911, Minneapolis Sunday Tribune.
Invasiveness: The Garden has some interesting history with the invasiveness of this plant. In 1976 Clinton Odell’s daughter Moana Odell Beim (who was president of The Friends of the Wild Flower Garden at the time) wrote in the Friends Newsletter, the Fringed Gentian™ about an argument her father had with Eloise Butler about planting Jewelweed. At the time Odell (the future founder of The Friends of the Wild Flower Garden) was a student of Butler’s and a frequent Garden visitor and helper. Eloise believed everything wild had a place in the Garden. She believed that what were called “weeds” should not be so called. The argument was whether Jewelweed should be maintained and planted when necessary. She won. Odell reported in his journal “The first year Jewelweed marched through the bog . . . the second year it started up the hill. The third year it went up and over the hill and something is darn well going to be done!” Workers were brought in and they pulled Jewelweed for days. Moana Odell Beim remembered many hours spent with her dad in later years pulling Jewelweed, particularly in 1945 when Curator Martha Crone reported another major effort to reduce the quantity of the plant. Martha had written a year earlier "The later flowers [of the season] found difficult competition in the abundant growth of Jewelweed and nettle. The seedlings of the Jewelweed appearing in such great numbers as to take complete possession of the garden. The program of their removal will greatly aid the establishment of desirable plants."
In the photo below from 2009 in the marsh at the Garden, you can see how extensively Spotted Touch-me-not can cover a lot of ground. Few animals will browse Spotted Touch-me-not as the sac in the spur of the flower contains a liquid that modern testing has shown to contain chemicals that are considered fungicides and therefore would be slightly poisonous to grazing animals. It is said however, to soothe a rash of poison ivy.