Make sure that you are using the right key. It is both a waste of time and an embarrassment to spend several hours attempting to identify a plant in the wrong key.
Read the key very carefully. If it is a good key, the author has spent a great deal of time selecting the right words. Much frustration results from misreading. There is a world of difference in the meaning of "and" and "or." They are not interchangeable.
Watch for weasel words, such as "mostly" and "usually." Most of us who write keys use these words as avenues of escape when we do not want to be pinned down.
Read both leads of the couplet before making your decision. The first lead may sound pretty good, but the second half may be perfect.
Do not base your decision on a single observation, particularly when you are being asked about measurements.
If neither lead seems to make any sense at all, you have probably made an error in keying and should not be in that section. Go back a step or two and check yourself.
Check to see if there is a glossary at the back (or front!) of the key. Authors vary in their use of certain terms and you will have to get used to the eccentricities of the writer.
Do not assume that a key says something
that it does not. In the second lead below, the author has not said that the
leaves are alternate.
1. Plants annual; leaves opposite.
1. Plants perennial.
If you are not confident about which lead to take, try both of them to see
where they will lead. One pathway should get you into difficulty fairly quickly.
If one side of a dichotomy will take you to a relatively small number of plants, check out their descriptions or look at drawings. This additional knowledge may be helpful to you. Also, as you gain more knowledge of the flora, you will be able to eliminate certain leads because they will take you to plants you know.
Learn to weigh the relative values of characters used in keys. Features of flower and fruit tend to be more important than those of plant height, for instance.
When you have arrived at a determination,
you should check it against a technical description, illustration or specimen.
