When you think of woodland plants, grasses are generally not the image that comes to mind. There are some grasses, however, that thrive in wooded areas. One common woodland grass at Blue Jay Barrens is Diarrhena Grass,
Diarrhena americana. Habitat descriptions for this species suggest it will be found in moist woods. Apparently it also does well in dry woods.
The areas of the woods containing Diarrhena had periods in their history when the canopy was much more open. Perhaps additional sunlight helps this grass become established in new areas. Most of the Diarrhena is now growing beneath a near 100% canopy and appears to be thriving. There must be some limiting factor at work here or the Diarrhena would carpet the entire woodland floor.
Diarrhena Grass can reach a height of three feet and produce some fairly thick stands, but the individual stalks are not so tightly massed that other woodland plants are excluded from the area. Several species of woodland wildflowers will bloom here in the spring.
I think this grass would be excellent for use in restoration of heavily eroding woodland areas. Even a thin stand tends to capture and hold fallen leaves. This keeps the leaves in place on steep slopes, so they can begin decomposing and recreating the woodland soil ecosystem. Some young researcher may want to look into this. I bet it would make a great graduate research project.
The seeds are held long into winter and are eaten by Turkey, Grouse and various songbirds. There have been several snowy years when I’ve seen myriad bird tracks and wing marks in the snow around these stalks.
Every December, I’m newly amazed at the beauty of the Diarrhena Grass, Diarrhena americana, growing in the woods. Cold temperatures cause the grass to take on the color of golden honey. With the addition of sunlight, the whole hillside glows.
The Diarrhena Grass covers a large expanse of wooded hillside that was once extensively logged. This section was much more open 40 years ago. I’m wondering if the grass colonized the more open situation and now persists in the shade or if the grass was already here and just survived through the period of more sunlight.
It’s odd to see what looks like a prairie in the woods. It might appear that some clearing would be appropriate to bring sunlight to the grass, but the near 100 percent tree canopy cover makes this a true woodland. The grass actually thrives in the shade. It might even have some physical adaptation that keeps it from being covered by falling leaves. The tree leaves seem to filter naturally through the grass stalks to form a thick layer near the ground. Seed stalks remain standing free and tall.
I think Diarrhena Grass could be a valuable tool for woodland restoration. The grass grows on the steepest of areas and would provide perfect ground cover for an eroding woodland hillside. The grass would catch the falling leaves and the process of building stable hillside soil could begin.
There are still many questions concerning growth patterns and behavior of Diarrhena Grass that I would like to have answered. What is the mechanism for colonizing new areas and why do existing stands not spread across the entire woods? The hillside in the foreground has a thick cover of grass that has remained unchanged for the past 25 years, while the hillside beyond is free of Diarrhena Grass. What factors cause one hill to be covered while the other remains bare?
The functioning of a Diarrhena Grass ecosystem certainly deserves more study. I know that many spring wildflowers are found growing with the grass, but I haven’t done any counts to see how species numbers might differ from those in the non-grassy woodland. It seems that the added cover might be attractive to ground nesting bird species, but this is another thing I don’t know. There must be insect species that utilize all this grass. Maybe there’s even a rare species that’s Diarrhena dependent. Looks like a lot of material here for someone’s graduate thesis.
