Seed coleus are inferior plants. They constantly want to flower, go to seed and then die, their mission being accomplished. The sterile hybrid cutting types are healthier, hardier, and can take full sun or shade or anything in between. If kept pinched, to promote branching, they will perform until the first freeze.

Below zero is too cold, a temp in the teens is not that bad. Most roses can take temps like that without too much damage. My attached garage has no windows. With no light source the temperature stays pretty constant. Are those in your garage exposed to light coming in a window? If so, that could be your problem. There is lots of heat in sunlight coming through glass. My unheated greenhouse gets into the 50s on these cold days if the sun is out. An outside digital thermometer on a south facing kitchen window read 56 degrees yesterday due to the sun. Another on a west facing window in the shade never got much past the mid 20s.

Hello everyone..I still a newbie here but still wanted to share.. Mine have been in my garage since the end of October since our first last frost.All the leaves dropped off shortly after that on my 5 foot one in a 5 gallon pot,while the leaves on my 2 gallon pot stayed on. It has been very cold here recently and I decided to check on my trees wrapped in blankets and covered with other huge pots, just to realize the temp in there was 29 degrees. it is my first time wintering these things, and since the little guy was in almost frozen mix, and the big one, not quite so because it was covered with blankets, I still decided to pull them into my shed since the temps in there are about 35 or so.. I hope they make it...They still look green and the next years buds look ok.. Keeping my fingers crossed.. I do not water since the cold soil seems to still be moist..I haven't had to water since October telling me that the plant is completely dormant and they were covered very well so they would not dehydrate. Thank you for all your advice and experiences.. Mike..:-)

Tao, I've kept osmanthus indoors for several years -- if you wait until night temps approach 0, then bring them inside to the garage for a few weeks to keep the winter chill going, you could then bring them inside to a sunny window and they'll probably respond with a burst of flowering. Then in spring, you can start leaving them out once night temps get above freezing (watch out for frosts, though!) and give 'em a second winter, and repeat the blooming in spring. The camellia will be harder to winter inside, and should be kept almost constantly to the 40s and 50s fahrenheit (sorry, we pathetic Americans don't know celsius!) until spring, and even then you may lose buds if you move it before it blooms. In both cases, the MH light will work fine, so long as you position it about a meter (hey, I'm trying here) away from the foliage so they don't burn, and consider keeping a small fan going -- both plants will benefit from fresh, moving air. Good luck! Jim