Problems in the Broccoli!! If brassicas, such as Calabrese, begin to show red discolouration on the leaves, this could be one of three possible problems, all relatively harmless and easy to solve. High or low temperatures, and/or bright sunlight and low water levels can cause stress to the plants, and they respond by colouring the leaves red. The red colour will slow water loss as it slows down photosynthesis and protects the plant for damage from the stresses it is experiencing. Another possibi