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: “Water seed-box”, Ludwigia decurrens]
It’s begun to cool off here in South Carolina, and I expect wherever you are…after all, it’s nearly time for Halloween, and there are plenty of signs in nature that things are starting to “slow down.” Besides the obvious autumn leaves, the fall-blooming have mostly already reached their peak, although there are a number of species that bloom even later. After the first few frosts, there won’t be many flowers at all. At least for a while.
On the other hand, you can sometimes see wildflowers blooming even after frosts, as long as they are in protected places. Here is a native wildflower that blooms mostly in the summer, but still gallantly puts out a few flowers as long as it can.
It’s a wetland species, and an annual. It can produce a fairly tall stem, up to 6 feet high or so. There will be plenty of narrow, sharp-pointed leaves. At the base of each leaf, two narrow flanges of tissue run down the stem for a way, giving a sort of angular look. The upper leaves are where you will find the attractive flowers, and these occur one at a time, within a given leaf axil. Each flower has four bright green sepals and four bright gold-yellow petals. Eight tiny stamens are generally present. Now this is a flower that presents a really good example of what we call an “inferior” ovary…that is, the seed-producing portion of the flower. In this case, all of the flower parts appear to arise at the very end, or apex of the ovary, and so the ovary is in a position below or inferior to the floral parts. (Other plants exhibit an alternative “superior” ovary, with the floral parts at the base of the ovary. A good example would be what happens with a tomato flower. The tomato, as it swells, has a “blossom end”…where it is attached to the flower. The position of the ovary, from species to species, is very important in separating different plant families.) Once pollination has occurred, the ovary of our mystery plant elongates considerably, often swelling somewhat toward the end. Plenty of tiny, pale tan seeds will be produced, and these will fall away once the matured ovary, now a capsule, splits open.
This plant is common in wet places, often in ditches or at pond edges or other marshy spots. It’s found from Maryland to West Virginia and well into southern Florida, as well as Texas and the lower Midwestern states. It has plenty of near relatives, many of which are most common in South America. Some of these are reasonably aggressive, and are considered serious pests in wetlands. Otherwise, it is more distantly related to some very popular ornamental plants, including evening-primrose, as well as the cultivated fuchsias. This yellow-blooming wetland herb probably won’t win many competitions in the flower shows, but it’s nice to see on a mid-autumn day, bravely blooming up to the bitter end. (Photo by Linda Lee.)