Muhlenbergia minutissima

Annual Muhly (and Similar Species)

A marshy field of tiny, short, wispy grasses, here represented by Muhlenbergia minutissima.

You can see the small size of these grasses. Sometimes they are reddish.

Here you can compare the size to my foot.

Now the view is really close, as you must be, to really see any of these tiny grasses.

Muhlenbergia minutissima in the hand shows its delicate seedhead.

Roots and leaves.

Use the 1/4-inch grid to see the size of these plants.

The spikelet is the basic unit of grass inflorescence. Here it is less than 1/16-inch long.

Each tiny spikelet contains two glumes and has a lemma and palea protecting the stamens and pistil.

How to Identify the Tiny Muhly Grasses

  When I first saw one of these grasses, in a marsh near Dogtown Lake (near Williams, AZ), I thought it looked like a mist over the ground. It was growing only ankle high, but it can get almost knee high in ideal conditiions. I know no other grasses so tiny and delicate. These grasses do not require a marshy area to thrive. They can cover any sufficiently moist ground, especially after monsoon rains. Look for them on mountain slopes.

Similar Species

  Most other Arizona grasses with tiny seedlings and delicate seedheads are much bigger. To identify the tiny ones, you will need access to a microscope and some very sharp tweezers to distinguish each of these, so it is beyond this treatment. But the three listed here have one more thing in common: all have equal glumes only half as long as the floret. Even more diagnostic are the hairs on the glumes in perfect little eyelashes. These hairs are tiny--only about 0.1 to 0.3mm long, so use you hand lens.

  On the chance that you are like me, here is how you can know for sure which is which:
  Muhlenbergia sinuosa (Marshland Muhly) has green anthers 0.6 to 1.2 millimeters long.
  Muhlenbergia texana (Texas Muhly) has purple anthers 0.4 to 0.5 mm and lemmas 1.3 to 2.0 mm long.
  Muhlenbergia minutissima (Annual Muhly) has purple anthers 0.2 to 0.7 mm and lemmas 0.8 to 1.5 mm.
  Note that if the anthers are purple and 0.4 to 0.5 mm long, and all your lemmas are between 1.3 and 1.5 millimeters, you still can't tell which species you have until you see that the sheaths and nodes are glabrous (M. minutissima) or strigulose (M. texana). (He can't care about this! He really can't... ...can he?)