If symptoms persist beyond 10-14 days, a second similar application may be needed. Two applications should suffice. A calcium imbalance or deficiency can cause black heart. This occurs most frequently during periods of moisture stress and rapid growth during periods of high temperature. If moisture stress continues, reapply calcium chloride or calcium nitrate once per week until the stress period is over.
Frequent irrigations are preferred.
A total of 18-20 inches of water may be needed in western Oregon. Soil type does not affect the amount of total water needed, but does dictate frequency of water application. Lighter soils need more frequent water applications, but less water applied per application. Because celery is often harvested late into the fall when frost can occur, irrigation for frost protection should be considered. Solid-set irrigation for late plantings allows water applications during a frost event to prevent frost damage.