Buttoning and Lack of Heads (Broccoli and Cauliflower)
Buttoning refers to premature formation of broccoli or cauliflower heads; these premature heads never size up. Buttoning is most common when transplants are too old and past the juvenile growth stage when transplanted. Other stress factors such as low fertility, low moisture micronutrient deficiencies, or disease and insects can also be causes. Strong healthy plants lacking heads can occur due to periods of extremely warm weather (days over 86ºF and nights over 77ºF).
Bracts (Leaves) in Cauliflower or Broccoli Heads
High temperatures or low soil moisture can result in the formation of bracts, small leaves, between segments in the heads of cauliflower and broccoli. Choose heat-tolerant varieties to avoid bract formation in heads.
Head Rot and Brown Beading (Broccoli)
Both problems can be caused by several factors. Reduced calcium uptake due to low transpiration rates under extended wet or dry conditions during warm temperatures, combined with rapid growth can result in either condition, even when soil calcium levels are high. Head rot results from bacteria breaking down the tissues under wet conditions, and brown beading results from individual flower buds aborting under dry conditions. Mixing varieties based on rate of maturity offers growers the only practical defense against either head rot or brown beading; selecting a later-maturing variety to be harvested along with your typical variety during those parts of the growing season when problems have typically occurred can reduce the risk of whole-crop losses during challenging weather conditions.
Oedema of Cabbage
Oedema is a physiological response of the plant to excessive soil moisture during periods of cool nights and warm, humid days. Many small scabby lesions form on the underside of the cabbage leaves. Avoid irrigation during times when day-night temperature variations are great. Oedema may be confused with thrips damage.
Ricing or Fuzziness of Heads (Cauliflower)
The development of cauliflower curds that appear fuzzy is called ricing. Ricing can be caused by exposure of the developing curds to high temperatures or direct exposure to sun, rapid growth after head formation, high humidity, and high nitrogen fertility.
Tipburn is a result of localized calcium deficiency in leaf tips, which can occur due to irregular soil moisture content or low plant transpiration rates even when soil calcium levels are high. Providing consistent irrigation and taking measures to prevent root-compromising disease can help reduce incidence of tipburn.
Yellow or Brown Beads in Broccoli Heads
Yellowing of florets may be due to an over-mature head, high storage temperatures after harvest, or exposure to ethylene. Brown beads in broccoli are areas where florets do not properly develop and die. Possible causes include nutritional imbalances, or feeding damage by insects such as harlequin bugs or tarnished plant bugs.