How many letters does the top answer for “(bot.) having three leaflets.” have?

The most common answer is trifoliolate (12 letters).

Crossword clue: (bot.) having three leaflets.

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

trifoliolate 12 letters web-def

(of a leaf shape) having three leaflets

(of a leaf shape) having three leaflets 50% similar → trifoliate, trifoliolate