An even supply of water is a prerequisite for the development of normal and tender kohlrabi tubers.
The kohlrabi must not suffer any stunted growth after the bulbs have started to develop, because this can cause the tubers to burst. The tubers always burst then, when heavy rain falls after dry periods. The outer walls of the tubers have hardened during the dry season and must crack, when the tubers start growing again due to heavy water supply. The evil will be remedied, if you bridge dry periods by regular watering. In contrast to the other types of vegetables, kohlrabi should be watered at shorter intervals with correspondingly smaller amounts of water, to make a too strong alternation between over- and below-normal levels of moisture. Dryness and hesitant development also affect the internal quality and lead to lignification of the tubers.