Brassica is a genus of plants in the mustard family. They are also informally known as cruciferous or cole crops. (No that is not a typo, it is derived from the latin word for stem.) Famous for being cold and frost tolerant, members of this genus include: cauliflower, cabbage, kale, garden cress, bok choy, broccoli, Brussels sprouts, rutabaga, kohlrabi, and turnips.
When temperatures dip, ice crystals form in the cells of plants. When the frost melts away, cold intolerant plants will be left with damaged cell tissues and leaves that are waterlogged and brown.
Cold-hardy plants like brassicas typically do not experience this damage and certain varieties can withstand temperatures below 28 degrees, most notably: broccoli, kohlrabi, kate, cabbage, Brussels sprouts, mustard and turnip. In fact, frost can actually improve the flavor of kale by bringing out the sweetness.
We plant brassicas all season long, and our winter plantings of curly kale went into the ground in our hoop houses this week. Protected by row covering to keep out the worst of the night time chill, they will keep us stocked in greens until we close for the season on December 20th!