Hollow stem in broccoli

Growers of sprouting broccoli, Brassica oleracea var. italica, find that plants developing during the summer and fall months have a high percentage of hollow stem. These experiments were conducted in the central coastal broccoli districts of California to study hollow stem and pith discoloration in relation to growth and environmental factors. Foliar applications of the trace nutrients boron, magnesium, manganese, copper, zinc, and iron during the growth of the crop had no effect on the incidence of hollow stem and pith discoloration. Close plant spacing reduced the percentage of hollow stem. Higher rates of application of nitrogen fertilizer increased the incidence of hollow stem. The hollow stem condition begins following the initiation of the central inflorescence, the “center bud.” At first these are elliptical transverse gaps in the tissues which gradually enlarge so much that the stem is hollow as shown in the photo. There is ordinarily no discoloration of the surfaces of these openings at harvest. However, pith breakdown and discoloration may develop during shipping and marketing.