How many letters does the top answer for “plant that reproduces by means of seeds not spores” have?

The most common answer is phanerogam (10 letters).

Crossword clue: plant that reproduces by means of seeds not spores

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

phanerogam 10 letters wn-def

plant that reproduces by means of seeds not spores

spermatophyte 13 letters wn-def

plant that reproduces by means of seeds not spores