This can be commonly found in broccoli and occasionally in cauliflower. The symptoms are internal and are usually not visible from the outside. Small cracks develop in the stem and enlarge as the crop matures. Tissues usually do not discolour. In some instances breakdown does occur.
This problem has been linked to a Boron-Nitrogen balance in the tissue. Calcium may also play a role in this disorder. Rapid plant growth tends to favour hollow stem.
Cultural practices that encourage uniform growth rates can reduce the incidence of hollow stem. Susceptibility varies with cultivar, choose less susceptible varieties. Cool broccoli immediately after harvest to inhibit bacterial activity in the stem.