Cabbages belong to the Mustard family that include broccoli, cauliflowers, kale and brussel sprouts. Cabbage demands even moisture to produce good heads. Mulch with compost, finely ground leaves, or finely ground bark to keep the soil cool and moist and to keep down weeds. Vigor and flavour decline with heat. Although cool weather enhances flavour, plants may flower (bolt) in extended cold spells in cold climates or in heat spells in warm climates.