Awn, glume, culm, rachis

It was winter when I first passed through the Sahyadris, many decades ago. I looked out of the window of a train at the amazing landscape: fantastic rock shapes covered with swathes of drying grass. Those expanses of drying yellow grass have drawn me out of the city year after year. From a distance you see hills covered by trees, but when the rock falls away too steeply for a tree to find stability, grasses cascade over the steep slopes, in shades of yellow, gold, or red. I’ve always wondered about the varieties of grass that one can see. Now, in the infrequent outings during the pandemic, I thought I would learn how to tell grasses apart.

Starting is never easy. I looked at books and guides, and wondered at why I never took to botany. I looked at the lovely words: rhizome, culm and spikelet, rachis, glume, awn and floret, bulb and crown, sheath, blade, ligule and auricle. I could hypnotize myself with words like this, fall in love with language. But in school, when I tried to study botany, I would open the books too late, and the words would become a wall I could never be able to climb. I never mastered the words, and never managed to look out at the vista of the subject from the top of that high wall. One learns a technical language to be able to read and understand others, not to create barriers for others. Now that I have all the time in the world, here are some notes to myself. In the analogy that I have drawn, the rest of this post is a set of spikes driven into the wall so that I can climb it quickly later. If you enjoy it, so much the better.

I am not about to become a late-flowering botanist, so I will not look at the structure below the ground: the root and the modified stem called the rhizome. All that I’ll need to know is that if the rhizome is present, then the grass is a perennial. The stem is what I start from, and that should be called a culm by people like us who want to know more about grass. The culm could have a part below the ground, called the rhizome, but I will learn about the stolon, which is the part above ground. Some stolons, like the ones in these photos, stand upright, but others, for example on the lawns outside my apartment, trail on the ground. Stolons have nodes, and leaves or roots can arise from these. These nodes are called crowns when leaves arise from them. If a grazer eats a culm, it is regenerated from a crown. The leaf is another thing to look at. Its sheath wraps around the culm; if the blade bends away from the culm, then you can see a little tongue near the bend. This is a ligule; and it prevents insects from crawling down the blade into the sheath to eat away at the culm.

The most interesting part of a plant is the flower, the floret is what you would call it if you are a grass gazer. Grasses are wind pollinated, and do not require the petals which other plants use to attract pollinators. The florets are held on a part of the stem called the rachis; it may be straight or branched. The flowers are contained in spikelets. At the base of the spikelet, close to the rachis, are two modified leaves called glumes, which hold the florets alternately along their length. The tips of the glumes are extended into the long pointed things called awns, which you can easily see in all the photos here.

I love awns; they are what made me take the photos.