Blackheart

There are cherries enough for all, as when we planted we took into consideration the needs of our feathered neighbors, so the birds do not miss the fruit when on our breakfast table appears a great wooden bowl —you have no idea what an artistic bit the chopping bowl becomes when utilized in this way—filled with clusters of blackheart and white-heart cherries and their leaves.

Source: wiktionary

“Here travelers sat beneath a great blackheart cherry tree growing among white rosebushes by the fence,” notes a 1937 American Guide Series book, “and watched the busy river traffic while they waited for supper.”

Source: wiktionary

Blackheart results from inadequate oxygen supply for respiration (asphyxiation) of internal tuber tissue.

Source: wiktionary

Calcium sprays of 10 to 20 pounds of Ca(NO₃)₂ or 5 to 10 pounds of CaCl₂ per 100 gallons of water per acre applied once or twice per week have provided good control in several trials and are considered most beneficial when blackheart appears before harvest, when plants may outgrow it, and when it is necessary to hold mature celery in the field.

Source: wiktionary