Grass
Types (Grass, Bunch Grass, Single-Stem
Grass, Rush, Sedge)
What’s a grass? In PlantID.net,
grasses include “true grasses”, sedges and rushes. If it looks like a grass, we call it a grass.
There are four types of grasses that are often easy
to distinguish. We use grass type in
searches, so they’re useful for you to know.
Bunch Grasses have grass spikelets
and grow from a single root crown. They look bunchy.
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Single-Stem Grasses also have grass spikelets but each stem grows from its own root, or
in colonies connected by stolons and rhizomes.
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Rushes are round – round stems and clusters of tiny 6-part flowers.
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Sedges have
edges – triangular stems and tiny, scaly florets.
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This is a good first
understanding of grass types and it’s fine to stop here if you like. But there is more to learn if you have the
appetite.
Bunch Grasses and Single-Stem Grasses are “true grasses”.
They have several distinguishing characteristics.
·
Cylindrical, hollow
stems, like straws, connect with solid nodes (knobby
knees). (Like
so many other generalizations, this is only mostly true. Dallis Grass, for
instance, sometimes has solid stems.)
·
Grass Leaves look
like what you’d expect (see more in Grass Leaves).
·
True grasses have
distinctive spikelets, made up of one-to-many
florets, growing out of 2 glumes.
Hollow stems connect with solid nodes (knobby
knees).
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Grass leaves have several parts.
Photo by Zoya Akulova-Barlow
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This spikelet has 2 florets inside 2 glumes
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This spikelet has 12 florets with 2 glumes at the
base.
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Bunch and single-stem
grass stems are formed differently
A grass can grow new stems in a couple of ways.
Diagram from wikiwand.com/simple/Grass
One way is to grow many stems from the crown at the top of a root ball. These extra stems are called tillers. Grasses
that expand this way are called bunch grasses.
Another way is to grow sideways shoots (stems) just
above or below the ground (stolons or rhizomes). These
shoots can grow new vertical stems and roots at their nodes. Grasses that expand this way are called single-stem grasses. They may
grow close together, but they don’t all crowd down to a single root crown, so
they don’t look as bunchy.
Rushes and Sedges are
grass-like, but different.
Rushes have round, solid stems, often with no
noticeable leaves. Their tiny, six-part flowers start green and often
turn tan or brown. Flowers form in
clusters either at the top of the stem or, apparently, on the side of the stem.
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Actually, what looks like a stem above the flower
cluster is not a stem but a bract.
Rush leaf blades can be inrolled, sometimes forming
cylinders. Other blades can be flat,
lying next to each other like iris leaves.
Others have only leaf sheaths
and no blade at all.
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Photo
by Keir Morse |
Photo
by Neal Kramer |
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Photo
by Neal Kramer |
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We have two genera
of rushes in California, and they’re pretty easy to distinguish. Here’s more on rushes.
Most sedges have edges. If
you run your hand along the stem you’ll feel that it’s triangular, with three
flat edges running the length of the stem.
You’ll almost always find sedges near or in water. Sedges often have long, narrow leaves,
typically starting at the bottom of the plant.
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Sedges have separate male and female florets in the
same inflorescence. Above, you can see female florets, protected
inside a smooth coating, underneath male florets with stamens sticking out.
There are several genera of sedges (some without
triangular stems). They’re pretty easy
to distinguish. Here’s more on sedges.
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Corrections/Comments:
bruce@PlantID.net Copyright: https://PlantID.net/Contributors.aspx |
