John Nelson is the curator of the A. C. Moore Herbarium at the University of South Carolina, in the Department of Biological Sciences, Columbia SC 29208. As a public service, the Herbarium offers free plant identifications. For more information, visit www.herbarium.org or call 803-777-8196, or email firstname.lastname@example.org.
[Answer: “American bur-reed,” Sparganium americanum]
You could call this the “spiny, green, ping-pong ball plant” if you wanted, and why not?
It is actually a very common, perennial aquatic species found throughout most of eastern North America (although absent in southern Florida), often forming stands along pond and stream edges and along spring runs. Clumps, which may be thick, come up from slender rhizomes. Its leaves tend to be long and bright green. When growing in deep water or at times of recent heavy stream flows, the leaves are slender and ribbon-like, swaying gracefully in the current.
The plants bloom in the spring and summer, when a flowering stalk emerges from the clump. These stalks, somewhat zigzagged, may be 2-3 feet tall at maturity. The flowers are quite small and essentially inconspicuous, but they are arranged in compact heads, or globes, or “balls,” at different points along the stalk. Female flowers form the lowest heads, sometimes up to 5 or 6 in a sequence. Several dozen flowers will be crowded into each head. Each flower is dark green, and bears a number of small curious bracts –not exactly petals– at its apex. There is one elongated pistil emerging from the flower’s ovary, and as these ovaries mature with time, the bases of the pistils become hardened and spine-like. The overall effect then is a dense, round head that is somewhat prickly. The male flowers, even smaller than the female flowers, are also compacted into heads, and these are smaller than the female heads. These are strung out on the stalk above and beyond the female heads below. (If you use your imagination, you might find a bit of similarity between this species and our common cat-tail, and indeed, botanists place both in the same plant family.)
In the early autumn, the female heads fully ripen, eventually shattering during the winter and releasing the mature, one-seeded fruits (still with the spine-like attachment). Waterfowl like to eat these fruits, and they’ve also been used by humans as a sort of wild grain, and even a coffee substitute. The plants are quite charming, and they make good additions to a pool or bog garden.
There is a little problem, though…
Here in the Southeast, our Mystery Plant is a true native species, and as such, would be great for home gardening. However, in the recent past, a very similar species, but exotic and weedy, has been offered on the market. If you are interested in buying these plants at a gardening center, make sure that you are not buying the species called Sparganium erectum (–oops, I’m giving away part of the answer now!). It’s hard to tell these two species apart, so you might want to consult with the friendly botanists at your local herbarium. In any case, please remember never to discard aquatic plants that you have been growing into a nearby creek or pond: the potential for spreading invasive species is too high. (Photo by John Nelson.)