Floating flower rises from mud

Now that it's warmed up, I've been thinking of doing some more aquatic botany.

A kayak or canoe is good for studying plants growing in lakes and creeks, but sometimes you just can't beat putting on some old tennis shoes and wading into an oozy-bottomed pond with the water maybe up to your waist. This is no time to be overly concerned with snakes, but a sharp attention to any visiting serpents would be a good idea.

The advantage a botanist has in such an approach is that the lower portions of the plants can be studied. You just have to take a deep breath and lean over, carefully feeling around for the lower stem, trying to avoid the little critters and bugs. When the stem is located, tug away until you can get the roots and rhizome, or whatever might be down there.

Properly prepared herbarium specimens of herbaceous plants will always include the underground (or water) parts.

Our Mystery Plant is indeed an aquatic species, its massive rhizomes way down in the cool darkness, firmly secured in the mud. It likes to grow in quiet water, but can be seen sometimes at the margins of streams. The rhizome will send up a series of long-stalked leaves, each with a dark green, somewhat heart-shaped or arrowhead-shaped blade. The blades typically come all the way out of the water, but sometimes remain submersed.

Blooming takes place all summer and well into the autumn. The flowering stalks, also from the rhizome, reach up to the surface, each stalk bearing a single, showy flower. Each flower is equipped with a series of outer sepals, eight or 10 or so, which are green toward the outside, but progressively bright buttery-yellow toward the interior.

Technically, there are petals, but they are tiny and inconspicuous. It's the sepals that make these flowers conspicuous. The sepals are curved inward and don't open up widely, so that the fully matured flower has the look of a yellow and green ping-pong ball. Each flower has stamens and a single massive pistil, which eventually forms a dark green, sort of jug-shaped berrylike fruit. A number of seeds will be present in each berry.

This species has about 12 or so relatives, all in the same genus, which occurs in North America, Europe and Asia. It is a common component in many freshwater habitats in all of the Southeastern states, reaching as far north as lower New England and getting into much of Texas as well.

Around here, I've sometimes heard people refer to these plants as a yellow sort of form of our regular water lily. But our water lily, which is Nympaea odorata, has white petals and is quite fragrant in bloom. (There are other rather profound floral differences, too, but no need getting into all that now.)

This week's Mystery Plant: Nuphar advena, spatter-dock or cow-lily.

John Nelson is the curator of the herbarium in the department of biological sciences at the University of South Carolina. The herbarium offers free plant identifications. Visit www.herbarium.org or call 803-777-8196.