5/19/2017 7:26:00 AM The lake where you live How water plants spread
Ted Rulseh Columnist
Plants which grow on land have one main way of reproducing. They produce flowers that get pollinated, then grow some form of fruit containing seeds. The seeds are dispersed in many ways, some simply scattering on the ground, some taking to the air on bits of fluff, some distributed with the help of birds and animals.
There are exceptions to this rule. Some plants, notably grasses, also spread by sending out underground shoots (runners) from which new plants spring up. Some plants can grow from cuttings of the stem, if planted in hospitable soil.
Water plants have more varied ways of reproducing. Most of them have flowers, a few of them showy, like water lily and spatterdock, and emergent plants like northern blue flag (from the iris family) and pickerelweed. The many plants growing submerged in the water have nondescript flowers which may or may not stand above the surface. These flowers lead to fruits that hold seeds.
But aquatic plants are resourceful; most of them don't rely on seeds alone. Some plants - water lily and hardstem bulrush for example - spread by way of fleshy underground structures called rhizomes. All summer long, as the plant's leaves make food through photosynthesis, nutrients are fed down to the rhizomes, which store substantial energy and grow through the bottom sediment.
After the leaves die back in winter, the rhizomes remain dormant until spring when the water warms. That's when the rhizomes send up new shoots. Some plants can spread quite extensively in this way. The rhizomes tend to be fibrous and tough. Once established, beds of rhizome-producing plants are extremely durable; new growth appears year after year.
Some submerged plants - large-leaf pondweed (cabbage weed) is one example - can sprout new growth from plant fragments which break loose from wave action or are cut loose by outboard motor propellers and settle to the bottom.
The fragments take root and grow and over time can form new colonies. Cabbage weed also spreads from seeds and by way of rhizomes. This is why cabbage weed can become prolific in a lake. Coontail, bladderworts and milfoils, including the nuisance invasive Eurasian watermilfoil, can also spread from stem fragments.
Another mode of reproduction is by turions, sometimes called winter buds. These structures grow at the stem tips of plants and fall to the lake bottom when part of the stem breaks off or when the plant dies and sinks. They lie dormant through the winter, and new plants sprout in spring.
Turions tend to be rich in starches and sugars, providing food energy when the new plants sprout. In fact, plants grow much faster from turions than from seeds.
There's one more mode of reproduction found in free-floating plants like the tiny duckweed. They product tiny flowers and seeds but multiply mainly by budding. The plant grows a bud that develops into a near-perfect replica; clusters of up to eight plants can form in this way.
Ted Rulseh, who lives on Birch Lake in Harshaw, is the author of the "The Lake Where You Live," a blog where readers can learn about the lakes they love - the history, geology, biology, chemistry, physics, magic, charm. Visit lakewhereyoulive.blogspot.com. Ted may be reached at email@example.com.