Below is an inlet of Falls Lake located in Eastern Durham County. Viewed from a car driving along a quiet country road, the inlet looks like a lush pasture with a small pond at the end. But the “crop” being grown here is a massive population of the invasive Common Water-primrose – Ludwigia grandiflora ssp. hexapetala, which has choked the entire inlet. The “pond” at the end is one of only two spots of open water in the entire area.
A closer look at the vegetative mass, the beautiful individual flowers, and the deep green foliage.
Common Water-primrose spreads rapidly by sending out runners into any unoccupied spaces. The growth and spreading process always starts with plants along the shore, but as the population grows farther out into the lake, runners can also be sent out from any part of the rooted or floating mass.
Even peninsulas of land that extend into the open water become completely covered with the Water-primrose. The plants root at the nodes so anywhere the runners contact soil, roots are established, and vegetative growth can continue at a rapid pace. Within the area covered by the Water-primrose, it is difficult to find any other plant life except for trees.
Below is a photo of this inlet taken in October, 2012, after the blooming period is over. The population then was not as extensive, allowing a view of the lake water. This is followed by a photo of the same area as it is this July. Note the large pole on the left in each picture.
Another Falls Lake inlet, located in Northwestern Wake County, shows an earlier invasive stage, where the Water-primrose has not yet completely covered the water. Note the large vegetative mounds along the shoreline.
In this area, runners have formed floating islands, and additional runners can be seen extending out from the these islands.
The Water-primrose has colonized a large beaver lodge at the edge of the lake, shown in the two photos below. Beavers use mud to build the lodge and hold the structural poles and sticks together. The Water-primrose’s runners take advantage of the mud, rooting as they go, climbing all the way to the top of the lodge.
Common Water-primrose has been a problem plant for years at Falls Lake, and has a huge impact on vegetative diversity. In addition to physically clogging waterways and lowering oxygen content, Water-primroses are also allelopathic plants, in this case secreting substances that inhibit or harm other plants nearby. The shallow inlets of Falls Lake appear to be a nearly perfect environment for the spread of this invasive plant.
Invasive Common Water-primrose was mentioned in a previous article on the Mitchell Mill State Natural Area. https://bwwellsassociation.wordpress.com/2015/07/10/an-early-july-glimpse-of-the-mitchell-mill-state-natural-area/