Why do tomatoes have hard white and green centers?
The early bearing variety tomatoes we planted this year has fruit that looks mature and ripe but have hard, green centers and in the edges of the top half of the tomato that is not palatable. The bottom 1/3 of the fruit is usable for canning juice, but off taste and not ideal by any means for what we want.
We have observed this very occasionally in red mature ripe looking fruit in previous years, but this year it is present on the all the fruit of the early plants, and a few of the later fruits, much more than is normal for us. We recognize this has been another season of cool, wet-early and hot dry-late weather. We water regularly, same as we did in previous years, late in the evening, for longer periods 2 to 3 times a week. We treat with a fungicide a couple times when first signs of blight appear. We have about 2000 sq ft of garden space, raise about 30 - 40 plants of early, mid, and late-large, all indeterminate variety of tomatoes, with the majority of early varieties as our preference. We rotate our tomato plants seasonally, as we have severe late season blight to manage. (We have talked at length with Isanti County Master Gardeners about this issue.)
Any thoughts about what we can do in the future to avoid this, short of asking for ideal growing conditions? Are we watering too much? Why is this year so bad and affecting virtually all the early variety plants?
Tomatoes with hard white tissue in the cross-wall and center of the fruit have a physiological disorder called internal white tissue. They often have few external symptoms. High temperatures during the ripening period are thought to trigger the symptoms. Maintaining a sufficient potassium fertilization program (soil exchangeable potassium (K+) level of 130 PPM in sandy loams) can reduce symptoms but may not eliminate them. Resistance to this problem varies with varieties. The following sites may be of interest to you.
It is best to avoid watering your tomato plants in the evening as that might allow the leaves to stay wet through the nighttime and that will favor fungal diseases. Information on late blight may be found at the following sites.