Last weekend, on an early-morning walk through my meadow, I happened upon an area inhabited by one of our most interesting native wildflowers — the spotted jewelweed. Attractive on many levels, the thing that really grabbed my attention was the beautiful arrangement of dewdrops on the plant’s leaves. Each one stood out like a little jewel in its own right, making the name of the plant seem especially appropriate.
The leaves of the jewelweed plant are covered with microscopic hairs that are able to trap a thin layer of air at the leaf’s surface. When rain falls, or when dew condenses out of the warm, wet air rising from the ground on a cool night, the hairs prevent the water from actually touching the surface of a leaf. As a result, the surface tension of water produces spherical droplets of water that seem to glow from within, even on a cloudy day.
There are actually two species of jewelweed that can be found in our area. One, the pale jewelweed, or yellow jewelweed (Impatiens pallida), is — get this — pale yellow in color. Much more attractive is the spotted jewelweed (Impatiens capensis), which I have chosen to focus my attention on today.
The spotted jewelweed is an unusual wildflower in the sense that it is an annual. This means that each plant must grow from a seed every year and cannot rely on any help from a root system that survives the winter. As a result, the spotted jewelweed constantly produces flowers throughout the summer, and it aggressively attracts pollinators with abundant nectar.
The chief pollinators for the spotted jewelweed are bumblebees and honeybees, but another important insect is the yellow jacket, a species of wasp that is often more curious than dangerous. Another important pollinator is the ruby-throated hummingbird. Since hummingbirds need a constant supply of high-quality nectar, the existence of the jewelweed, which can produce 2.5 milliliters of nectar that is about 40 percent sugar per flower per day, is an extremely important source of food. But the jewelweed does not provide this food without a motive of its own.
Because the plants are propagated only by seeds, they must produce a lot of them, which, in turn, requires the assistance of many pollinators. The flowers first produce stamens that release pollen. A pollinator visiting the flower at that time can only pick up pollen and carry it to another plant. A day later, the same flower will see its stamens wilt and be replaced by pistils. Now the pollinators can only deliver pollen and fertilize the “female” flower.
By producing different reproductive parts at different times, the flowers reduce the chance of self-pollination, which would result in offspring that are similar (or identical) to the parent plant. Then, by producing flowers that provide an attractive supply of nectar on a daily basis, the plant encourages multiple visits to the same flower over the course of two days. In this way, the plant increases the odds that it will produce the maximum number and variety of offspring.
But why stop there? In addition to producing the beautiful orange and yellow flowers that catch the attention of pollinators and photographers alike, the spotted jewelweed will also produce another set of flowers that are small, green and closed. These flowers produce no nectar, and actually don’t even open up. Their sole purpose is to produce seeds by process of self-pollination that the more colorful flowers specifically try to avoid. This, in essence, is an insurance policy. The real magic is in the way the seeds are dispersed.
Both flowers produce the most unusual seedpods that I have ever seen. When ripe, the pods are green, translucent and noticeably “swollen.” At this time a pod that is illuminated from behind will reveal the silhouettes of the seeds hidden within. As the hydrostatic pressure in the pods increases, the slightest touch can cause them to “pop.” This explains the jewelweed’s other name — “touch-me-not.”
When pods pop, their sides whip themselves into tight coils, throwing the seeds up to four feet away from the parent plant in the process. This is a wonderful thing to see, and I must confess that I have spent more than a moment or two playing with jewelweed seedpods. They are the equivalent of living bubble wrap, and you just can’t seem to stop until all of the pods have been popped.
The most extraordinary thing about the plant is the fact that the two different flowers produce different kinds of seedpods. The smaller flowers, which produce seeds from self-pollination, produce much smaller pods that send the seeds flying much shorter distances. This increases the likelihood that seeds will fall in a spot that was already appropriate for the parent plant, giving its offspring the chance to grow in a good spot again.
Meanwhile, the larger flowers produce larger pods that send their seeds flying over longer distances, looking for new places to grow.
Look for the spotted jewelweed in wet to damp areas. The succulent stems are quite delicate, but they are able to support the plant until the first frost of the year. The fact that the plants are in continuous flower until the first frost will make them easy to spot. If you find the flowers, you will also find the seedpods and discover the joy of popping them open.
Bill Danielson has worked for the National Park Service, the US Forest Service, and the Massachusetts State Parks. He has been a professional writer and nature photographer for 19 years and he also teaches high school biology and physics. Visit www.speakingofnature.com for more information, or go to Speaking of Nature on Facebook.