What season and climate for red cabbage?

Red cabbage is a cool season crop just like green cabbage and needs cool weather to head firmly, roughly 15 to 22 C, with the best colour developing in cool conditions. In the plains it is a winter crop, with nursery raised in early autumn and transplanting a few weeks later, while hills grow it over a longer cool season. In heat the heads stay loose, may not colour well and pest pressure rises. Time the crop so heading falls in your coolest weeks. Confirm exact sowing dates for your region with your KVK.