We are in Hawai'i on the cusp of USDA 12a/b.
We had one hibiscus growing very poorly when we bought our place, a pinkish probable Rose of Sharon type.
I introduced a second Chinese Red type a few years later.
It did poorly also.
During last year's volcanic eruption, they both came alive and began acting very healthy, shaking off pests on their own, and growing and flowering like they never had before.
Apparently, during the periods when we were inundated with the SOx gasses evolved by the eruption, our soil became acidified.
And, they loved it.
I have since purchased sulphur pest and soil treatments for them, although I have not used them yet.
I have just purchased a large yellow flowered Chinese type to add to the stable.
My problem is that the older pink plant is very stunted, whizen, and mis-shapen because of its years of very poor growth.
It and the newer Red Chinese plant need pruning and shaping badly.
My other problem is that they both have been blooming all "winter" and are still doing so like they have never done before.
I'm reluctant to prune while they are blooming so actively.
I've noticed that our HOA normally has their yearly grounds maintenance done in August or September.
Their hibiscus, crepe myrtle, and others are severely pruned back at that time.
It's like they take a hedge trimmer and cut their large older hibiscus off flat about 2' high every year.
It is now actively growing and beginning to bloom.
Everything I read about pruning hibiscus says to prune in the spring.
I'm thinking of pruning in the "autumn" when the HOA has theirs done.
Any reason to not do so?
Your seasons are far different than the mainland, so go with the locals.
