Winter vegetables like broccoli and cabbage are very cold hearty. But we've had big fluctuations in temps, which is what I've read is when they are in danger. We've even had lows down to the teens and lately some rare wintry precipitation (sleet, snow), so on those nights, we've used burlap sacks as blankets.
These were used to import coffee, then later as packing materials -- they came to us by way of our friends at Wild Birds Unlimited. Burlap allows for breathing and is quick to dry when there's sun.
They have some ability to hold a form, and create a tent....like with the tall broccoli.
Here's an after image, of the difference between uncovered (left) and covered (right).
Here, a few cabbage in the row are covered with one burlap blanket. We'll see in a few days, if this scheme worked in this latest blast of wet and cold weather.
All images (c) Molly & Sandor
Kiss My Grits Blog (Walk for Farm Sanctuary)