“As the fall weather finally begins to turn cooler, gardeners are faced with this annual dilemma: Will those green tomatoes in the garden ripen?
“In many areas of California, fresh garden tomatoes remain edible until late October or early November. They may not be pretty ... but they are still a heckuva lot tastier than any tomato you’ll find in a grocery store. By mid-November, remaining tomatoes are subject to harsher, colder, wetter weather leading to more outbreaks of blight diseases, insect infestations and bird pecking.
“How do you tell when a green tomato, harvested early to prevent freeze damage, will ever turn red and ripen? This can simply be done with a sharp kitchen knife. Harvest a tomato typical of the majority of green tomatoes on your plants. Look at size but pay particular attention to fruit color. Slice through the center of the tomato. Closely examine the seed within the fruit. If the seeds are covered with a clear gel which cause them to move away from the knife, then that fruit will eventually turn red and ripen. If the seeds are cut by the knife then those fruit will never properly ripen. Compare the color and size of the tested fruit when harvesting tomatoes. ... Most similar fruit will eventually ripen and turn red.”