Question
I have two hardy Hib. trees that I keep in large 1'1/2" depth. height and width. I live in Tennessee and so it's warm but we do get cold winters. Do I need to bring these inside for the winter? If so, around what time of year should I be doing this? I've been struggling finding info on this. I need to find info on Pruning, and over all care. If you can help me, Thanx a BILLION!!   Sara  

Answer
Hi Sara,
Thanx for your question.  Are you certain that the trees you have are hardy hibiscus?  Hardy hibiscus are botanically known as Hibiscus moscheutos and will survive winters to zone 5.  Most of Tennessee is in Zone 7 and the hardy hibiscus will do fine here.  You won't need to bring the plants in for the winter.  I would move the pots so the trees aren't exposed to the cold north wind because even in Tennessee, there are going to be some cold spells.  Potted plants are especially vulnerable to the cold north wind.  Hardy hibiscus turn brown and die to the ground with the frost.  They will emerge in May of the new season.  Their leaves are a dull green and the flowers are usually large and showy and somewhat flat.  Hardy hibiscus are generally used like shrubs out in the yard and grow about 3.5 - 4.0 feet tall.  Tropical hibiscus is botanically known at Hibiscus rosa-sinensis is not hardy in your zone.  It is a plant typically bought in houseplant and shrub form, grown as a plant that people put on the patio for the summer and then bring indoors for the winter.  It has glossy, darker green leaves and the flowers are showier in some ways than the hardy and will come in colors unavailable in the hardy hibiscus such as yellows and oranges.  The flowers are somewhat smaller than the hardy hibiscus and they are more trumpet-shaped with the stamens visible.

http://www.plantoftheweek.org/image/hibiscus.jpg   tropical hibiscus pic
http://klishis.com/pictures/p2005/hibiscus.jpg      hardy hibiscus pic

Tropical hibiscus must be brought indoors before temperatures fall below 50癋/10癈.

For hardy hibiscus, cut them all the way to the ground once the frost has killed them back.  They will emerge in May and you don't want to cut anything off or you're going to cut off blooms.  Tropical hibiscus can be lightly pruned in the winter just to keep shape and keep them from getting lanky.  Tropical hibiscus will go semi-dormant in the winter and stop or slow blooming considerably.  There will be leaf-drop too but don't worry.  The plant is ok.  Just water enough to keep it from drying out and don't feed it.  Once spring comes back and it gets warmer, the plant will come back.  For hardy hibiscus, side dress the plant after it emerges with well-composted manure, water once a week and it will be fine.  I hope this helps.
Tom