spring strut

Bill could hear the trickle of water running in many small streams, could see the sun heliographing off the broader expanse of the Kenduskeag. And the smell was the same, even with the dump gone. The heavy perfume of growing things at the height of their spring strut did not quite mask the smell of waste and human offal. It was faint but unmistakable - a smell of corruption; a whiff of the underside.
Source: It by Stephen King

What does the noun strut mean in this context? I understand the definition of the verb strut - walk in an overly proud or self-important way.

Thank you.

Hi.
Hmmm. This is a funny one. Mr K seems to be personifying the season. Or at least the growing which happens in the spring. The word strut is used as a noun there but still conveys the arrogance of the verb to strut.
Does this help enough?

Thank you. Awesome.