Annual and seasonal fluctuations in Falls Lake water levels often lead to dramatic swings in the population size of many shoreline plants, particularly the annuals. At times, sustained droughts can create large mud flats in the shallow inlets of the lake, providing a perfect habitat for plants that live in the usually narrow bands of mud along the lakeshore. Valley Redstem (Ammania coccinea) is an excellent example of a shoreline plant that exploits low water levels to produce large surges in population numbers.
Valley Redstem is a native annual with long, narrow, opposite leaves and small but beautiful deep rose or purple flowers arising in the leaf axils. It has a long, sustained blooming period July through October and produces abundant fruit. During the blooming period, it is common to see flowers and fruits in various stages on the same plant.
Below is a closer look at a flower. The anthers and the central style are a bright yellow in color and are easily seen against the deep rose purple of the petals.
Xanthium strumarium , the Common Cocklebur, is another plant that often colonizes dried areas of exposed mud at the lake margins. The small, narrow red leaves and fruits of Valley Redstem can be seen in the following photo (indicated by the white pointers), providing an understory population among the larger Cockleburs. The leaves, fruit and stem begin turning red in late summer and early fall, explaining the origin of the common name Redstem.
The red fruits and stem are seen below in a photo taken in October.
Valley Redstem is a member of the Loosestrife family, the Lythraceae, a diverse group that includes the popular small landscape tree, Crape Myrtle (Lagerstroemia indica), and the problematic and invasive Purple Loosestrife (Lythrum salicaria) shown below. Purple Loosestrife degrades wetlands by competing out the native plant communities and totally altering the ecology of an area. It is one of the worst non-native invasive plants in our northern states. Fortunately Purple Loosestrife is not well established in the South.
The flowers of Purple Loosestrife have six petals rather than the four petals of Valley Redstem; the color is very similar but is more variable.
For more information about Purple Loosestrife in North Carolina check out the link to the N. C. Plant Conservation blog below.