How many letters does the top answer for “a genus of fossil trees.” have?

The most common answer is ulodendron (10 letters).

Crossword clue: a genus of fossil trees.

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

ulodendron 10 letters web-def

A genus of fossil trees.

a genus of trees; the plane tree. 50% similar → platanus

a tree of the genus eucalyptus 50% similar → eucalypt

a tree of the genus fagus. 50% similar → beech