A volunteer asked me this morning why her large tomatoes are so slow to ripen this year. I could appreciate her passionate desire for those juicy berries (yes, it is a berry) to be salad-ready, but restraint is the better part of flavor, I always say.
The basic answer to the age old problem of green tomatoes is temperature. Lycopene and carotene are the responsible pigments for a tomato’s typical coloration. These pigments are produced when temperatures range in from seventy to seventy-five degrees, temperatures typical of late summer. We have had long stretches of summer temperatures exceeding eighty to ninety degrees. Pigment production ceases at these blistering levels.
What you do not want to do is remove more leaves to increase light levels, or water more, or fertilize more, or anything more. The maturity date of each variety is an important number to remember when planning and planting your solanaceous crops. Temperature is the key environmental cue for tomatoes, so if you just cannot wait for the fruit to ripen naturally, remove tomatoes just showing signs of color and store them in a dark, enclosed space maintained at room temperature. This should help you out “paste” the natural ripening rate.
Josh Steffen, Horticulture and Facilities Manager