The most common and most likely answer to this crossword clue is the 8 letter word SPHAGNUM
I've seen this crossword clue in The Guardian
S
P
H
A
G
N
U
M
More clues leading to the result SPHAGNUM
Buddy explains!

The straight part
We know that "growth in bogs" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case growth in bogs = sphagnum.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SPHAGNUM mean?
SPHAGNUM noun- Any of various widely distributed mosses, of genus Sphagnum, which slowly decompose to form peat.