Nutrient deficiency that affects Broccoli. Hollow Stem can be caused by excess nitrogen fertilization, especially during warm weather (no internal discoloration); or boron deficiency (dark brown internal discoloration) .
Hollow stem resulting from boron deficiency can be controlled by soil (preferably) or foliar application of low rates of boron. Boron deficiencies are more common on sandy soils and may be detected in a soil test. Be careful not to over apply boron as high rates can cause toxicity – cupping and scorching of leaves.