What's the plural form of knotwort? Here's the word you're looking for.
Answer
The noun knotwort can be countable or uncountable.
In more general, commonly used, contexts, the plural form will also be knotwort.
However, in more specific contexts, the plural form can also be knotworts e.g. in reference to various types of knotworts
or a collection of knotworts.