Charles, We have a similar question to John’s, regarding winter watering.
We have a large polytunnel here in southern Germany, it is planted with a wide range of salad, parsley and kale too.
The outside temperature is below freezing here day and night recently, though it is often sunny and bright. The temperature in the tunnel rises to 10 or 15 degrees during the day.
The red russian kale is looking rather floppy. We do not feel able to water with the temperature so low. The surface of the beds are dry, though deeper it is moist.
Can we risk watering, when it might freeze solid at night? Will the roots freeze?
Do you have an idea why the kale is unhappy? Is it the rising and falling temperature?
Hoping you can shed a little light!
Jonathan and Mareike, Alchemila Garten