Grasses (Including Sedges, Rushes)
Overview of Grasses
Description of "True Grasses"
Inventory of Grass Families and Species
During 2014 the Grassland Biodiversity Survey was conducted at
Sky Meadows State Park by the Smithsonian Conservation Biology
Institute. As part of the survey, several grasses, sedges and rushes
were identified as inhabitating Sky Meadows. This survey provided
the starting point for identifying various grasses inhabiting Sky
Meadows; however, further research will be necessaary before a
comprehensive inventory of species is completed. Currently
nine species of grasses, three species of sedges, and one species
of rush have been identified from one family of grass, one family
of sedge, and one family of rush.
No database has been selected for information concerning grass species.
However, the United States Department of Agriculture's Fire Effects
Information System (FEIS) will probably provide the "core" database for
most species information as well as general entry structure. Additional
information from other sources will be "integrated" with the FEIS. Other
primary information sources may include:
USDA Forest Service
FDGIF (Virginia Department of Game and Inland Fisheries)
VDF (Virginia Department of Forestry)
The general information format and grass entries that may be used will
probably be derived from the Fire Effects Information System (see
"Databases" section of website for discussion of FEIS). Some modifca-
tions in structure have will be employed. The following is a delineation
of the modified FEIS format that may be used.
CITATION: The common grass name(s) followed by the current scientific
COMMON NAMES: List of generally accepted common names.
SCIENTIFIC SYNONYMS: Partial list of previously used scientific
TAXONOMY: Current taxonomic classification with discussion of varities
or subspecies, as well as hybridization characteristics.
NATIVE STATUS: Includes information pertaining to whether the grass is
native or introduced as it occurs in the United States and Canada.
GENERAL BOTANICAL CHARACTERISTICS: Includes information
describing basic botanical characteristics (e.g., form, leaves, seeds, etc.). REGENERATION PROCESSES: Regeneration from vegetative parts
and from seeds.
HABITAT TYPES: General habitat types.
SITE CHARACTERISTICS: Includes information on topography, soil
types and elevations where species occurs.
SUCCESSIONAL STATUS: Includes information on shade tolerance,
occurrences as pioneer and/or persistent species.
SEASONAL DEVELOPMENT: Flowering and fruiting dates.
GENERAL DISTRIBUTION: The general North American (United States
and Canada) distrubution of grass species.
SKY MEADOWS DISTRIBUTION: Distribution of grass species within Sky
Meadows State Park.
IMPORTANCE AND USES: Importance of grass species to wildlife and
livestock, value for rehabilitation of disturbed sites, consturuction material
and ornamental use, and any medicinal characteristics.
Overview of Grasses
Grasses, or more technically graminoids, are monocotyledonous,
usually herbaceous plants with narrow leaves growing from the base.
They include the "true grasses", of the Poaceae (or Gramineae) family,
as well as the sedges (Cyperaceae) and the rushes (Juncaceae). The true
grasses include cereals, bamboo and the grasses of lawns (turf) and
grassland. Sedges include many wild marsh and grassland plants, and
some cultivated ones such as water chestnut (Eleocharis dulcis) and
papyrus sedge (Cyperus papyrus). Uses for graminoids include food
(as grain, sprouted grain, shoots or rhizomes), drink (beer, whisky),
pasture for livestock, thatch, paper, fuel, insulation, construction, sports
turf, basket weaving and many others.
For the Nature Guide, only those graminoids belonging to the "true
grasses" (Family Poaceae) will be listed. Facquire County has well over
one hundred species of Poaceae; Sky Meadows State Park is anticipated
to have a significant portion of these species.
No descriptions of grass species are currently available.
Description of "True Grasses"
Even for the professional botanist, identifying grasses can be difficult.
Unlike most trees, where only a small number of physical characteristics
are necessary for identification (e.g., trunk, branch, roots, leaf), grasses
require a substantial number of complex and often difficult to recognize
characteristics. Combined with the technical botanical terminology used
with grasses (terminology that is unfamiliar to most of the general public),
grasses, so ubiquitous and important to all humans, are appreciated in
general, but little understood in the specific.
To assist the visitor to Sky Meadows Park, the following article,
"Puzzled by Poaceae?--A Grass Identification Workshop," is copied in
full. Presented by Tim Miller, Extension Weed Scientist, (Washington
State University) at the Washington State Weed Conference on
November 3, 1999, Mr. Miller provides an excellent introduction to
the essential characteristics and terminology necessary for identifying
grasses. This information will prove invaluable when later grass
descriptions are provided in the Nature Guide.
WHAT IS A “GRASS?”
The word “grass” is used to describe those plant species most commonly
used in lawns and pastures, or used to cover road shoulders, or even as
slang for items as diverse as money and marijuana. The English word
grass probably comes from the Old High German . . . word gras, generally
used to describe any herbage suitable for livestock grazing.
Botanically speaking, what makes a grass a grass? Three major
characteristics separate the grass family from all other plant families:
The flowers lack petals and are borne between bracts in a leaflessinflorescence.
The leaves are flat, long and slender, and form a sheath around thestem.
The stems are round, generally hollow, and somewhat swollen at|the nodes.
Remember: although an unknown plant specimen may possess one or
even two of these characteristics, that does not necessarily mean you
are looking at a grass. It is the combination of all three characteristics
that defines the grass family.
HOW IMPORTANT IS THE GRASS FAMILY?
The grass family is one of the largest of all plant families. Some 170
genera, including more than 1400 wild and cultivated species, grow in
the U.S. and Canada alone. Worldwide, about 10,000 species from 700
genera comprise Poaceae. No plant family comes close to Poaceae in its
importance to world agriculture. Wheat (Triticum aestivum), rice
(Oryza sativa), corn (Zea mays), oat (Avena sativa), rye (Secale
cereale), barley (Hordeum vulgare), and the many species of sorghum
and millet provide the grains which are the staff of life for nearly all of
the peoples on earth. Many species of range and pasture grasses, in
addition to the grains listed above, are used for livestock forage and feed.
Turf and ornamental grasses are used and appreciated for their
durability and beauty throughout the world (the namesake for the grass
family, Poa, is the genus from which current cultivated varieties of
bluegrass have been developed). Finally, grasses such as bamboo lend
their service for construction and plumbing in many countries. Clearly,
humans and grasses are closely tied, and have been for centuries.
HOW DO WE IDENTIFY THE GRASSES?
The current system of plant taxonomy is based primarily on reproductive
structures–it is the flowers of the plant, more than any other character,
that really define the species. Consequently, observing a plant’s
inflorescence is the best way to positively identify that plant. This is
especially true of grasses, which often resemble each other so closely that
species differentiation using only vegetative characters is very difficult.
Grasses are difficult to identify because many of their reproductive and
vegetative structures are unique to the family. They are also very small,
making observation extremely tedious. If we ever hope to learn grass
identification, we have to have a good understanding of what these
structures are, and where they are located.
Vegetative Structures. All grasses are monocotyledonous plants (or
monocots). This means that grasses have only one cotyledon, which is
the first or “seed” leaf that emerges from a seed. In actuality, the first
structure that emerges from a grass seed is a cylindrical, soda straw-like
structure called a coleoptile which is rigid enough to push through the
soil. It is from within this tube that the fragile cotyledon grows upward
to the surface and unfurls. As the grass plant continues to grow, leaves
are formed, each of which emerges from within the leaf that preceded it.
Think of a grass as growing much like an extending car antenna, except
this antenna has leaf blades growing out on alternate sides of the stem.
The characteristics of the blades, including blade width, whether the
expanded blade is rolled or flat, whether or not the midrib is distinctly
visible on the upper surface, presence or absence of hairs, and whether
newly emerging blades are rolled or folded, are all commonly used for
grass recognition and identification. The “tube” or “sleeve” part of the
leaf (the part that wraps around the stem) is termed the sheath. The
degree to which the sheath is open (the edges merely overlapped) or
closed (the edges fused together into a seamless sleeve) and the
presence or absence of hairs are commonly used vegetative characters.
The entire leaf, then, extends upwards from a node, up the sheath, and
outward to the tip of the blade.
The structures at the junction of the blade and sheath are also of interest.
This is the collar of the leaf, and there are two types of structures that
grasses may posses in this region. The first are auricles, finger-like
projections of the upper edges of the sheath that appear to wrap
around the stem. The presence or absence of these paired structures is
a useful identification feature. Auricles may be short, long, or absent and
smooth or fringed with hairs. The second structure is the ligule, a
small projection located between the blade and the stem. To best observe
this structure, gently pull the blade away from the stem, and it will pop
into view. The ligule may be completely membranous, a ring of hairs, or
hairs that form a fringe on a membranous base. The type of ligule, as well
as its length, overall shape, and texture of the leading edge are key
Reproductive structures. The individual flowers of grass plants are
called florets. A typical floret has three stamens (male flower parts) and a
single ovary with two stigma (female flower parts) at the tip. The ovary is
borne between two tiny, leaf-like bracts. The outer bract is the lemma, and
the usually smaller, inner bract is the palea. These structures are usually
green when the plant is in flower, becoming chaffy to leathery as the seed
ripens. The length, texture, and number of major veins (nerves) of the
palea and lemma all aid in species identification. In addition, lemmas are
frequently awned, and this presence (or absence) of an awn, where it is
inserted (e.g., at the tip, middle, or near the base), as well as its length
and shape, are good characters to note.
Florets may be borne singly, or in clusters up to 14 or more. These
clusters of florets are termed spikelets, each with two additional bracts
at the base. These bracts are the glumes, which may be variously awned
and nerved. Spikelets will break away from the stem or disarticulate in
one of two ways: (1) above the glumes, leaving the empty glumes on the
plant after the spikelets have dropped, or (2) below the glumes, in which
case the glumes remain attached to the spikelet as it drops. How the spike-
lets are borne within the inflorescence is also important for identification.
If the spikelets are attached directly to the main stem, the inflorescence is
called a spike. Usually spikes are single within an inflorescence, although
some species (e.g., bermudagrass) bear multiple spikes. If each spikelet is
borne on a short or long stem (pedicel) which in turn is attached alternately
up the main stem, the inflorescence is called a raceme. Finally, if the spike-
lets are borne on pedicels which in turn attach to other branches and
ultimately to the main stem, the inflorescence is called a panicle. Panicles
are usually diffuse and open, although some (e.g., foxtail and timothy) are
densely congested and very spike-like.
IDENTIFYING GRASSES USING A KEY
A plant key is designed to help the user quickly identify an unknown
plant through the use of carefully selected choices. The choices often are
in mutually exclusive pairs; that is, one plant can only be accurately
described by one of the two statements. This is termed a dichotomous
("forking") key. For example, the contrasting statements may be "ligule
< 1mm long or absent" versus "ligule > 1 mm long." For a given plant,
then, only one term applies: either the plant has ligules shorter or longer
than 1 mm, not both. But remember that plants are living things, and
living things are always somewhat variable. To guard against possible error,
always observe the character in question on several different organs or
plants. By averaging your answers, you are more likely to choose the
correct description. Keys are often numbered and/or lettered to aid in
matching the dichotomous statements, so the correct comparisons are
made by the user.
Keys are powerful tools, but, like any road map, a key must be correctly
used to arrive at the correct destination. A user who incorrectly answers
the often technical choice is lost and will arrive at the wrong answer, or
eventually arrive at a fork where neither statement accurately describes
the unknown plant. Careful use of correct botanical information is a must
to successfully key plants! One last thing to consider about keys: they
only allow you to identify species actually used when constructing the
key. If, for example, you attempted to identify Indian ricegrass (a
nonweedy native species, Oryzopsis hymenoides) using the enclosed key,
you would key the plant to bentgrass (Agrostis). This is because Indian
ricegrass, with its particular combination of characters, was not used
when this key was constructed. Other grass species might result in
failure to find an accurate description at one of the forks, or in a different
incorrect identification. So always compare your plant with a description
and illustration or photo of the answer to eliminate the chance of
incorrect identification. If, after several attempts, you still are not
convinced that your specimen matches the description, try a different
key (such as Vascular Plants of the Pacific Northwest) or send the
specimen to an authority who can positively identify it. If you must,
collect another specimen after it has matured and try again to identify
it using a key using reproductive structures.
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