Hi Tabby:

First - congrats on your new greenhouse! It sounds like you've got a great project to help brighten up your coming winter.

As to accessories, you will definitely need a heater to warm the greenhouse through the winter. You may need a thermostat depending on what sort of heater you get. A fan (or fans) is probably a good idea. You may also need to have some sort of a vent to let hot air vent out in the spring & summer months, as your greenhouse will heat up a lot on sunny days.

You will need to decide what uses you will put the greenhouse to. Do you want to just winter stuff over - as in have the plants go dormant & start regrowing in the spring? Or do you want to have the plants actively growing in the winter. That will determine how much heating capacity you need. Just keeping a small greenhouse at 35 degrees Fahrenheit will not need a big heater, but nothing will be actively growing in that sort of a greenhouse.

Different plants will need different minimum temperatures to ensure growth - many orchids need minimum night temperatures of 50 or 55 Fahrenheit. Herbs and leafy vegetables can probably get by with overnight minimums of 40 or 45 degrees. Some tropicals do not want to drop below 60 or 65 Fahrenheit.

Cannas and many elephant ears are perfect for cool dry storage (a garage, attic or basement). Just let the frost kill the tops. Then dig the roots, clean off most of the soil & store in slightly moist peat moss.

I would think that most salvias could survive in a cool to cold greenhouse in a dormant state over the winter. They probably would do better on the dry side as well.

Hope that this helps!

Dan