How many letters does the top answer for “one who makes trees his study, or who is versed in the knowledge of trees. howell.” have?

The most common answer is arborist (8 letters).

Crossword clue: one who makes trees his study, or who is versed in the knowledge of trees. howell.

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

arborist 8 letters web-def

a specialist in treating damaged trees