I saw this on a Scotts Bonus S fertilizer bag.

Problem:
An adjective was used where an adverbial phrase is required.

Explanation:
“Anytime” is an adjective.

It’s an anytime event to have Bill Clinton visit our donut shop. is an example of the proper use of “anytime”. The adjective “anytime” tells the reader/listener the what type of event it is to have Bill Clinton visit the writer/speaker’s donut shop.

As you start to read the notice on the fertilizer bag — “Apply anytime weeds” — it seems that you are supposed to apply a particular type of weed (“anytime weeds”).

This makes no sense, especially when you then read “are actively growing.”

Some readers might unconsciously drop in “that” to get “Apply anytime weeds that are actively growing.”

Huh? What’s an anytime weed, and why should I apply actively growing ones to my lawn?!

Instead, the writer of the notice wants to tell you when to apply the fertilizer, not when to apply the “anytime weeds”.

What’s needed in the notice on the bag is the adverbial phrase “any time”, which is equivalent to “whenever”.

Getting stuck in the longest line happens any time that I try to pick the shortest line at the grocery store. is an example of the proper use of “any time”. The adverbial phrase “any time” tells the reader/listener when the writer/speaker gets stuck in the longest line.

Solution:
“Apply any time weeds are actively growing.”