Grass, Rush or Sedge?

"Sedges have edges, rushes are round; Grasses have nodes right down to the ground". There are many variations of this little rhyme, which demonstrates that the problem of telling a grass from a rush from a sedge is commonplace and many attempts have been made to provide a short and easy way to tell them apart - but none of the variations of this rhyme truly work in all cases. Such is the variety of these groups of plants (especially the grasses), that coming up with a 'quick fix' is not easy, but this page will hopefully lead you in the right direction.

There are two parts to this section and you may have arrived here via the first part, which covers rushes and sedges. If not, you can check those groups if you click here, or you can continue from the link at the foot of this page. Coming to terms with grasses is a big step for someone learning botany and these plants can present a seemingly impossible identification task. This page will hopefully indicate the key characters that separate grasses from all other plants, as well as introduce you to some of the terminology which is used for the various parts of grasses.

It is often not realised that grasses, rushes and sedges are all flowering plants. It is common to hear people talk about 'flowers and grasses', as though grasses do not have flowers; but this is simply because of the false belief that flowers are always bright, colourful and showy. Grasses, rushes and sedges clearly have flowers, but they tend to be green, brown or straw-coloured and don't obviously contrast greatly from their vegetative parts.



Grasses     

The family Poaceae contains all of the true grasses and is one of the largest plant families in the world. Indeed, there are very few places one can go and not see at least one species of grass and this highly successful and adaptive family has members in all main habitat types. When you consider that grasses include such diverse groups as bamboos, cereals and the major constituent of lawns and meadows, you get an indication of both their variety and their importance.

Grasses may be annual or perennial, with the perennials being either tussock-forming, or spreading to form mats by means of stolons or rhizomes (creeping stems or roots). Most importantly, most species have round, sometimes slightly flattened, but not angled stems, which are hollow except at the nodes. The nodes are joints on the stem that help to distinguish grasses from rushes and sedges. The leaves of grasses typically consist of a flattened blade, but this may also be inrolled at the edges. The leaves clasp the stem at their bases and typically have a sheathing, lower section that wraps right around the stem. Unlike sedges, these sheaths are split down the side opposite the leaf blade and can easily be pulled away from the stem without tearing the sheath. Where the lead blade meets the leaf sheath, there is a small structure called a ligule, which may bed membranous (like those of sedges) or may be a fringe of hairs.

In most grasses, the flowers are bisexual and have both male and female parts, consisting of typically three stamens and two stigmas, though there are some exceptions to these numbers. The flowers are greatly reduced, with effectively no visible sepals or petals. A single flower is referred to as a floret and florets are held in spikelets (either singly or in clusters) and the spikelets then gathered into spikes. Each spikelet has two small bracts called glumes at its base and each floret within the spikelet has two bracts known as a lemma and a palea (more information is given on this in the grasses help page). This might sound complicated, but suffice to say that this complex arrangement of florets and their bracts readily distinguishes grasses from other grass-like plants once the basic structure is understood. All grasses follow this basic flower structure, but their great diversity comes in the variation in how these flower parts are either contracted together or spaced out.



Grasses - growth style     
Broad-leaved Bamboo Meadow Fescue European Marram Common Sheep's Fescue
Scattered, woody stems
from creeping roots
Scattered, herbaceous stems
from creeping roots
Large, arching tussocks
Small, dense tussocks
Purple Small-reed Great Brome Rigid Fern-grass Bread Wheat
Open colonies of stems
Dense colonies of individual
plants
Tiny plants in cracks & crevices
Crops


Grasses - stems     
Common Canary-grass Annual Meadow-grass Wood Meadow-grass Black Bamboo
Stems have nodes which may
be bent or hairy
Non-flowering stems have leaves
along their entire length
Stem separates easily from leaf sheath
Bamboos have glossy, woody
stems


Grasses - leaves     
Chinese Fountain Bamboo Japanese Millet Common False-brome Common False-brome
Bamboo leaves are relatively
short and broad
Leaves may have pale stripe
down the centre
Leaves often with hairs
Leaves may be grooved
or ridged
Blue Fescue Two-rowed Barley Reed Canary-grass Common Reed
Leaves may appear tubular but
are just strongly inrolled
Leaves may envelop the stem
with an auricle
Leaves have a ligule where they
meet the stem, which may be
membranous
Ligule may be a line of hairs


Grasses - flowerheads     
Early Pampas-grass Velvet Bent Common False-brome Downy Oat-grass
Large, plumose heads with
thousands of tiny flowers
Open, many-branched heads
with tiny spikelets
Drooping spikelets
More simple, unbranched heads
Common Canary-grass Black-grass Wood Millet Common Reed
Tight heads with elaborate bracts
Simple spikes of densely packed
flowers
Slender heads with solitary florets
The simplest flowerheads, a
single row of solitary florets
Rough Dog's-tail Meadow Brome Sea Fern-grass Common Millet
Compact heads with bristly awns
Simple spikes of densely packed
flowers
Tiny, stiff spikes
Robust heads with chunky florets


Grasses - flowers     
Red Fescue False Oat-grass Common Cock's-foot Heath-grass
Young florets, tightly packed
against each other
Floret with mature,
feather-like stigmas protruding
Florets with mature,
creamy stamens protruding
Florets over mature,
stamens and stigmas dropped
Triticale Common Quaking-grass Argentine Needle-grass Common Millet
Densely packed florets
Enlarged florets in compact
spikelets
Tiny florets with long awns
Solitary, rounded florets




To view rushes & sedges, click here.