Trilliums: The Dark Side
By Bruce Rottink, Volunteer Nature Guide & Retired Research Forester
At Tryon Creek State Natural Area (TCSNA), springtime is trillium (Trillium ovatum) time. Walking through the forest, who wouldn’t be delighted by these tough, brown, lumpy trilliums that look eerily like a piece of poop (“feces” for the delicate among you)? Surely something we can all….. What? Oh, I’m sorry! I forgot that you’re used to only seeing the parts of trillium that are above ground. Well then fasten your seatbelt pilgrim, ‘cuz today we’re taking a dive into the dark side. Thanks to an anonymous donor with hordes of trilliums in their private forest, we’re going to look at the part of the trillium that’s underground!
What’s Down There Anyway?
Pictured below is a whole trillium. The level of the soil is marked with the black dashed line. Above ground is the familiar white flower, the large green leaves (which are technically “bracts”), and the long stem (in botanical terms it’s actually a “scape”). As you can see, the two main things underground are the large, lumpy brown rhizome and the stringy white roots. When straightened out, the roots are about 30 cm (1 foot) long. I excavated this plant very slowly and carefully. The vast majority of the roots survived the extraction process, although there was some minor root breakage in the process. The orange ruler is 12 inches (about 30 cm) long.
The photo below gives a close-up view of only the subterranean elements of the trillium. The two principle parts are the profusion of whitish roots and the thick brown rhizome.
In the close-up photo below, the roots look pretty unremarkable. However, they do seem to branch less than many species I’ve observed. You might notice that the roots don’t originate evenly over the length of the rhizome, but rather are concentrated on the right-most end of the rhizome which bears the scape (stem) of the plant. This is the younger end of the rhizome. The left (older) end of the rhizome bears very few roots. Also notice the abrupt, rather than tapering, left end of the rhizome. It almost looks like the older (left) end of the rhizome has been cut off. In fact, as the rhizome ages, the oldest part of the rhizome is decayed away, leaving a flat end.
Cool, but how old is this trillium?
People have long been fascinated with the question of how old a particular trillium is. They have attempted to determine the age of a rhizome by counting leaf scars. The green arrows in the picture below are indicating just two of the “lumps” which are the leaf scars. The fact that the older end of the rhizome keeps decaying away is just the first of two major hurdles to correctly aging the plant.
A view down the rhizome from the young end of the rhizome gives a different, and perhaps more instructive view of the leaf scars. From this perspective each of the leaf scars is a little shelf, with the leaf coming out of the flat top side of the shelf. The top of each shelf appears to be full of some “knobby” structures, which I have cheerfully assumed are the healed-over stubs of the vascular tissue (like veins) that connected the leaf to the rhizome. The green arrows point to individual shelf-like leaf scars.
It has been widely assumed that by counting the leaf scars you could determine the age of the plant, much as you might count tree rings. If the trillium produced only a single stem (scape) per year, this would be a wonderful system. Sadly, it is not so simple. This is the second major hurdle to aging a trillium plant by counting leaf scars. Namely, that the trillium can produce more than one stem per year, and thus more than one leaf scar per year. The example used above produced one leaf this year. However, another trillium, which I had growing in a pot in my backyard, is pictured below. Clearly it has produced two stems (scapes) this year, and thus will leave two scars in the future. As a side note, you can see that both of these stems blossomed.
The rhizome of the trillium I dug out of the forest has, as near as I could determine, 45 leaf scars. Assuming that each year it produced either one or two leaf scars, it is somewhere between 22 and 45 years old. But that’s just the part of the rhizome that hasn’t rotted away yet. So much for being able to determine the age of trilliums!
So what does the rhizome do?
One of the rhizome’s main functions is as the food storage organ for the plant. The huge amount of energy stored in this rhizome over winter is the reason trilliums shoot up so quickly in the spring. The trilliums don’t have to manufacture food as they burst up from the ground. Instead they draw upon the massive food reserves already in the rhizome. Below is a longitudinal (“lengthwise”) cut through the rhizome. This rhizome is approximately 1 inch (2.5 cm) in diameter. The inside has approximately the feel and texture of a potato. Of course after the spring burst of growth, the green parts of the trillium above ground take on the task of replenishing the food reserves for next year’s scape, bracts and flowers.
The trilliums of TCSNA are probably a lot older than we first imagined. They are not only the Princesses of the Forest, they are tough, long-lived members of our forest community.