How to make an identification key for plants

Do you mean something like the decision tree sometimes seen in the back of botany or horticulture books? Like if monocot go to line 3, if dicot go to line 25. Then each subsequent line has further decisions to better identify what sort of plant we’re trying to identify? Of course a web based app would work differently, but the underlying concept would be the same.

I think the main design decision will depend on what sort of database schema you have available. With adequate data it’s likely some kind of user interface can be developed to aid in identification, but it’d likely be bespoke code. WP can accommodate such a thing provided the data is available in mySQL format or could be converted to mySQL.