The most common and most likely answer to this crossword clue is the 8 letter word GENTIANS
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More clues leading to the result GENTIANS
Buddy explains!

The straight part
We know that "plants" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plants = gentians.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 GENTIANS mean?
GENTIANS noun- Any of various herbs of the family Gentianaceae found in temperate and mountainous regions with violet or blue flowers.
- The dried roots and rhizome of a European gentian (Gentiana lutea), used as a tonic.