Which ferns would grow well on an east-facing balcony with about 1 hour of morning sunlight? I would like to plant several different varieties for maximum visual impact. Could they survive winter?
Overwintering perennials in containers is one of the biggest challenges faced by container gardeners in our zone, and balcony gardeners in particular. The freeze-thaw cycle is the main problem; that is, the melting of the water in the container’s soil during sunny or warmer spells, followed by freezing when the temperatures dip again. This is what kills a plant’s roots over the winter. Your most important starting point is the container itself: it should be as large as possible (the more soil it can contain, the more insulation it will provide), and it should not be clay or any porous material which will swell and crack when the soil inside it freezes and thaws. Your local nursery can help here. There is such a good selection of containers available now.
Even as an experiment (and isn’t that what gardening is all about?) it is well worth trying to grow some of the hardiest of hardy ferns in your containers. Most experts say that for container perennials to have a fighting chance of overwintering, they should be hardy to two zones colder than our own. In Toronto (Zone 6) these would be ferns that are hardy to Zone 4, or even lower. On your balcony, you will also need ferns that thrive in shade. Here is the Toronto Master Gardeners’ guide to Hardy Garden Ferns, which provides a useful chart of shade-lovers and hardiness zones. As you’ll see, most of the ferns listed are hardy to Zone 4. When you are shopping for plants, do make sure to read their labels, which should provide the information you need. Informed nursery staff should be able to help you with your choices, although they may well caution that despite best efforts, plants in containers sometimes do not survive the winter.
Here are two good general articles: https://www.enjoycontainergardening.com/overwintering-container-perennials.html , Container Gardening with Perennials and here, a useful article from Garden Making: How to Overwinter Perennials in Pots . Unfortunately, on a balcony we don’t have recourse to the recommendations that work for homeowners: to move pots to an unheated garage, or to “heel” plants into the garden for the winter. Instead, container size will be key, as will protection from overly drying and the windy conditions that some balconies experience. Very best of luck with your container planting.