InfoVeg

For example, Acer rubrum is given as a choice, along with its varieties; Quercus rubra is not shown, only its varieties.

If one goes in via families, one seems all the appropriate choices

RKP:
Your problem seems to be generic in that when one searches on a text string one finds only the ends of the twigs of taxonomic tree. For example, because Quercus macrocarpa var macrocarpa is recognized, Q. macrocarpa is omitted from the picklist. We need to expand the picklist to include all species, even when a var. (or vars.) is recognized.