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Illustrated Help - a step-by-step guide
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Use the
illustrated key to
generate a list of grasses matching easily measured features.
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Use the
extended key where you have only a piece of
the grass rather than a complete specimen.
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Use the
Grass Checklist to link to a description
of a known grass.
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Hints on using the keys
Filling in all the boxes in the order they appear
is the wrong way to use the keys.
- Do not guess.
It is preferable to leave boxes empty rather than guessing. When in doubt, leave it out!
- Start with 3 or
4 obvious features. Don't try to fill in all the boxes at the beginning.
You can return to this page and add more features as often as you need.
- For measurements,
an average of several specimens is best. For some measurements, you will need a
hand lens and a millimetre ruler.
- First-time users should
read through the following interpretation section for an understanding of the methods
used in this treatment as well as help on how to measure each character.
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For definitions, see the glossary.
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Further information can be found in the reference list
and in the links to other websites
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- Measure height of the grass from the ground surface to the top of the plant
along the stem, including the flowerhead in the measurement.
- To measure the ligule, it is best to use a hand lens and millimetre ruler.
- In the illustrated key, you do not have to measure ligules less than 1 mm long. For
ligules less than 1 mm, just enter 1. You can distinguish smaller ligules in either
the extended key or by comparing grasses.
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- Measure the leaf blades at the widest part of the blade. Measure several
blades and take
an average. If your leaves are folded or strongly inrolled, you will have to
flatten them to get an accurate measure. The measurements in the key are for the full
width of the blade. It is preferable to leave this field blank if you cannot determine
whether or not the blade is inrolled or folded. For narrow blades such as in some
species of fescues (Festuca) you may need a hand lens to make a reliable
measurement.
- The leaf sheath wraps around the stem. In some grasses, it is closed nearly to
the top. Sheaths may also overlap for much of their length, or they may be open.
Overlapping and open sheaths come apart easily. Closed sheaths tear along the suture as
you try to open them.
- Auricles are little "ears" or projections at the junction of the sheath and the blade.
These may resemble little claws or may simply be rounded swellings. Auricles are not part
of the ligule.
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- The interpretation of spike in this key is not a botanical one.
If the flowerhead looks like a spike, and you cannot see little branches at the
base of the spikelets, choose spike. Several grasses do not technically have
true spikes, but to a non-botanist the flowerheads look like spikes. In
this key, such grasses will be found in both categories.
Beware that the immature flowerhead of several grasses (such as
Agrostis) look like spikes. Spread out the flowerhead to check for
obvious branches. If they are visible, enter "branched" not "spike" in the
key.
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- Measure the flowerhead length from the base of the lowest spikelet
if your flowerhead is a spike, or from the point at which the lowest branch is
attached if it is branched.
Exclude the awns from the flowerhead length measurement.
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- The spikelet is the flowering unit of the grass, comprised of two (rarely one or none)
glumes - small bracts at the base, and one or more florets.
- Measure carefully from the base of the spikelet to the tip,
excluding awns and branches if there are any.
- If the glumes are longer than the enclosed lemma (or lemmas), simply measure the
length of the longest glume.
- If the seeds have started to fall off from the flowerhead, leave the spikelet
length field blank. Many grasses, such as bromes (Bromus) have short glumes
but very long spikelets.
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- Florets are the individual reproductive units of grasses and consist
of the lemma, the palea and the enclosed reproductive components -
including the anthers and pistil which may be visible with a hand lens.
- Count the number of florets (the 'future seeds') in each spikelet.
Floret number is a highly diagnostic feature, so take the time to count their number
carefully. There can be from 1 to 20 or even more florets. If your plant is mature and
the seeds have begun to fall off, don't use this characteristic!
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- Most grasses have two glumes (bracts) at the base of each spikelet, but some,
such as Lolium have only one, or even none, as in Zizania.
- Using a hand lens, look closely to see if the lower glume
(also called the first glume) is shorter or longer than the first floret.
The first glume is determined by the point at which it is attached to the stalklet. The
glume which is attached closest to the stem is the first glume.
The ratio of first glume to first floret is a very useful character, so make the
effort to figure it out.
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- Awns are bristly or hairlike projections from the lemmas, and sometimes the glumes. Some
grasses don't have them - in which case, enter 0 in the box. If your grass has awns,
measure them from where they are attached to the lemma or the glume.
- In the illustrated key, only lemma awns are used as a character.
- In the extended key, you can enter measurements for both lemma and glume awns.
If your grass has them,
measure them from where they are attached to the lemma.
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- Look carefully for the attachment point to the lemma, another important
distinguishing characteristic. Awns in some species arise at the tip of the lemma
or glume, but in others they arise from the back of the lemma.
- Most
bromes (Bromus) and oatgrasses (Danthonia) have bifid tips - with two
'little teeth' that also arise at the tip of the lemma body. You may have to pull the
floret apart and use a hand lens to be sure.
- Answer 'along the back' if it attaches more than halfway down the back
of the lemma. Answer 'at or near the tip' if it seems to be coming from the
tip, from between
two 'little teeth', or very near to the tip.
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