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Vegetables and Plant Pathology

When it occurs in celery, this disorder is known as blackheart. Blackheart may appear at any stage of celery growth. Usually, it becomes evident at the 8-10 inches tall stage or later. The new growth at the center of the stalk begins to die back. Leaf tips brown at the margins, and the discoloration and death of tissues can progress down the leaf into the stalk rather quickly. At times the black stalks will extend down to the stem plate. Blackheart is primarily a dry rot, however, secondary soft rot bacteria often invade the damaged tissues, turning the center of the celery stalk into a slimy dark brown to black soft rotted mass.

Blackheart is closely associated with water balance in the plant and with calcium levels in the crown leaves. Any time the plants are stressed for water, calcium metabolism may be disrupted and blackheart initiated. Other factors that have been associated with blackheart and moisture relations are:

• Calcium availability, or calcium utilization: vigorous plant growth, varietal susceptibility, moisture deficiency or excess, high relative humidity, high temperature, low transpiration rate, possibly associated with unbalanced potassium, high fertility level, high soluble salt level, low Ca:K ratio, low Ca:N ratio, high K level, high N level, and high Na level that may reduce Ca uptake.