Never been much of a gardener, so 10 years ago I bought a house with a mostly asphalt backyard. So, different season of life now, my wife and I are starting a small garden of mostly food bearing plants.
We're located in Calgary, Canada where we have long winters with lots of Chinooks (warm wind that will randomly bring the temperature up to 10-20 C and melt everything).
Our raspberries are planted below ground and are thriving. This year we added some herbs (thyme, sage, etc...) and strawberries. However, as we're limited in space, these are planted in the above ground planter box. The guy who sold us the herbs suggested that freezing over the winter for many of the perennials would be fine, but our Chinooks could likely kill the plants if they were planted above ground. Any truth to this? How can I ensure that my plants survive our strange winter? Can I just shovel lots of snow onto it and hope the planter box never gets the chance to thaw?