Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
In our 2019 seedless watermelon variety trial, we are seeing higher than normal levels of hollow heart. Hollow heart is an internal split or void in the flesh of the watermelon between the 3 carpels or fruit sections. Research at the University of Delaware has shown that inadequate pollination is a major factor in hollow heart. Hollow heart is generally more severe in the crown set. Varieties vary considerably in their susceptibility to hollow heart. Dense fleshed (crisp) varieties, mini, and personal type watermelons have lower hollow heart incidence.
This year, pollinizers in a number of fields have declined prematurely (this was evident in our variety trial). Reduced pollen availability caused an increase in hollow heart during later sets in susceptible varieties.
Hollow heart in seedless watermelon