Plant height and plant spread are already included in the data fields for every plant in the database. If you want to enter the height of a dahlia, please submit a data proposal for that plant.

Deborah, your comment was in the generic Dahlia entry near as I can tell. As you likely know, dahlias range from 6" to 6' (or more) in height. If you narrow your search to a specific cultivar, you will find more specific information re height, spread, and even florescence height. If that information is not in our database for a specific cultivar, you could do some online research to find out the answer, then submit a data proposal (as Zuzu suggests) to add that information to the entry.