Grass Spikelets (Spikelet, Floret, Glume, Lemma, Palea, Awn)

Just as Asters have flower heads that hold many tiny flowers, grasses have spikelets that hold one-to-many florets. In the grass world, a floret is a tiny grass flower with no petals, just male and female parts covered by bracts.

In a grass spikelet, the florets line up, one after another, with a pair of glumes at the base.

Diagram from countrysideinfo.co.uk/grass_id/grasses.htm

Florets and glumes sometimes have bristle-like awns extending from their central vein. In the diagram above, the florets have awns and the glumes do not.

In the real world, spikelets and their parts vary a lot. Here are some examples.

A Grass Spikelet: Slender Wild Oats – photo by Wilde Legard

A Grass Spikelet: Rattlesnake Grass – photo by Wilde Legard

Sometimes all you can see of a spikelet are glumes that completely cover the florets, as in Small Fescue, below. Other times, the glumes are very short and you can see the woven florets of the spikelet, as in California Brome.

Glumes cover the spikelet: Small Fescue Festuca microstachys Photo by Zoya Akulova-Barlow

Glumes are quite short: California Brome Bromus carinatus var. Bromus carinatus Photo by Wilde Legard

Long glumes may open up, revealing florets tucked inside. This spikelet has hairs at its base.

California Oatgrass
Danthonia californica
Photo by Steve Matson

Awns are very helpful in identifying a grass. An awn is a bristle that extends from a vein, similar to the bristles you find on Black Oak leaves.

Awns can be absent, short or long. They can be straight or bent. They can grow out of the glumes or florets or both. You can see awns on all the spikelet pictures above except for Rattlesnake Grass.

Two bracts, called the lemma and palea, cover and protect each floret’s reproductive parts. The spikelet below has been opened up to show them, but when a spikelet is all tucked up, you’ll mostly see the glumes at the base and a lemma covering each floret.

Aelwyn - https://commons.wikimedia.org/w/index.php?curid=1221626

Wind Pollination

When mature, each floret opens up and discharges its pollen and receives outside pollen. If pollen from another plant falls on the floret’s feathery stigma and reaches the ovary, the floret develops a grain with a single seed inside.

Want more?

· Grass Inflorescences

· See Jean Turner’s excellent article on Grass Identification.

Corrections/Comments: bruce@PlantID.net Copyright: https://PlantID.net/Contributors.aspx