Orange Jewelweed (Impatiens capensis) is a common late summer, early fall wildflower in the Pennypack Preserve. It is water-loving and tends to grow near the creek, or in ditches or low spots next to the creek trail. The full-size plant can grow several feet tall and may form large clumps of beautiful orange flowers. The name Jewelweed has been attributed variously to its bright flowers, or to the appearance of the leaves when covered with water droplets as can be seen in the photo below.
It’s other common name is Spotted Touch-Me-Not. This name comes from the fact that the mature seed pods contain a spring mechanism. When touched they explode and expel the seeds a considerable distance, an obvious aid to seed dispersal. The seed pods are the elongated green structures in the lower left of the photo. Flowering occurs progressively over time. In the photo, some flowers at the top are in bud stage, others are fully developed, and some have been pollinated and have formed seed pods. The curved tube at the back of the flower is called a nectar spur, and obviously stores nectar. Bees and hummingbirds are common pollinators. Apparently hummingbirds are more effective than bees at gathering nectar from curved nectar spurs and are efficient pollinators. However, some bees have evolved the ability to cut the base of the flower to “steal” the nectar without pollinating the flower.
A less common relative of Orange Jewelweed is Yellow Jewelweed (Impatiens pallida) also known as Pale Touch Me Not. It is similar to Orange Jewelweed but has pale yellow flowers.
It is also found in the Preserve in similar areas where Orange Jewelweed is present. An interesting biological feature of Jewelweeds is that in addition to typical insect-pollinated flowers, they also have what are known as cleistogamous flowers. Cleistogamous (meaning “closed marriage”) flowers are small and do not open. They are self-pollinated and thus do not permit interchange of genetic material between plants. They serve as a safety mechanism for the plant in case there is a shortage of pollinating insects. Jewelweeds are annuals and depend for their survival on producing seeds each season. The mature plant dies in winter. Cleistogamous flowers ensure that some seeds will be produced whether or not the plant is pollinated. The cleistogamous flowers on Jewelweeds are tiny, only 1-2 mm in diameter, and green. I tried to find a good internet picture to guide me, without success. I searched several plants, but only saw normal flowers. Apparently, stressed plants produce more cleistogamous flowers, presumably as a defense mechanism. Pennypack plants are apparently unstressed. On searching my photos I did find one shot with a contender.
If you look at the above photo at the top leaves, there are 1 or 2 tiny green flowers on short stalks hanging down. These are my best guess for being cleistogamous flowers, but I still need to find a good documented photo on the internet to confirm. Since there is progressive flowering, these alternatively could be nascent buds of normal flowers. Other Pennypack Preserve plants which have cleistogamous flowers include Common Violets and Hog Peanut Vine.