How many letters does the top answer for “relating to the growth of hair.” have?

The most common answer is crinicultural (13 letters).

Crossword clue: relating to the growth of hair.

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

crinicultural 13 letters web-def

Relating to the growth of hair. [R.]

of or relating to a hair 67% similar → pilar

of or relating to growth by auxesis 50% similar → auxetic

relating to or suitable for growth 50% similar → growing