I think "dormancy" is the wrong word -- unlike deciduous trees that shed their leaves and stop growing during the winter, osmanthus stays green and can put out new growth if it gets good light.

However, growth does slow down, and like you said, it needs cool, humid conditions to stay healthy indoors in winter. Here are some tips:

1. Give it at least some direct sun during the day, and/or supplement natural light with a compact fluorescent or other grow light (but don't put a light so close to the plant that it gets too hot and burns the leaves!)

2. Keep it evenly moist -- don't ever let it dry out, but never leave the plant sitting in water or you risk rotting the roots.

3. Give it moving air! This is the "secret weapon" for indoor growers -- a lot of problems like spider mites, weak, yellowing leaves and general decline can be reduced, if you've got a fan going that keeps the air moving around the plant.

4. Thoroughly wetting the foliage with a sprayer a couple of times a week won't raise humidity for more than 30 minutes, but it does keep the leaves clean and dust free, and helps combat pests.

5. If you can move the plant to a cool spot near a window or door at night, do it, so long as the plant is not soaking wet -- cold and wet roots are a bad thing.

Hope this helps!

Jim

I am not sure what dormancy really mean, but Al, who is active in Bonsai forum, wrote an excellent post about dormancy. I think some evergreens do need some kind of resting period (I hope this term makes some sense), without this, they will continuously grow for a period of time but eventually decline to death even right in summer time. Actually this is exactly what happened to my two plain Osmanthus.

You are right about the caring in the winter, they need the cool, humid and ventilated spot.

Thanks for the help.

Tao

Unlike plain Osmanthus, the four season does not need a
winter dormancy period, instead it grows and open flower
buds in winter, if you provide it cool (not that cool, below 20C) and sun light. In fect, winter is the most important flowering season for the four season.

It will formancy in summer, just after its fast leave grow.

Thanks for the information.

I think you are right, since they have been flowering since November in my basement, it's around 72 degrees with 50 percent humidity. So far they still have great looking leaves. I just moved to this house this year, before the move, my Osmanthus (plain and four seasons) always had brown tips. I think it was warmer and lower humidity.

This year we have extremly mild weather in Ottawa, around 38 degrees, my garage is around 45 degrees and 80percent humidity. To be on the safe side, I am going to put them there for two weeks, this is going to be like their natural habitat. At least it's not going to do any harm to them.

Tao

In my passive green house( no ice nor frost), a young Os plant (4 seasons type) is growing with clusters of new flowers now. I think that Os can stand moderate cold and is very comfortable at mild winter weather area.The original habitat is along Yangtze River and southern China.