Eggplants (Solanum melangona) come in a wide variety of sizes, shapes and colors, but one variable is more important than all the rest in selecting a ripe eggplant: the skin has to be shiny or glossy. If it is dull, the eggplant is overripe.
Eggplant Climate and Maturing Times
Eggplants can be grown as herbaceous perennials in U.S. Department of Agriculture plant hardiness zones 9 through 12, though they are typically grown as warm-season annuals throughout USDA zones 4 through 10.
Depending on the variety, most eggplants are ready for harvest about 65 to 80 days after transplanting from nursery seedlings. If you grow eggplants from seed, expect to wait 100 to 120 days.
Signs of a Ripe Eggplant
In addition to looking for glossy skin, gently press your finger into the eggplant. If the flesh is hard, with no give, the eggplant is immature and too young to pick. If your finger makes an impression that quickly fades, the eggplant is ripe and ready to harvest. If the impression lingers, the eggplant is soft and is likely over-ripe.
Eggplants are edible once they reach one-third of their mature size. They're generally at their prime at about two-thirds of their mature size. The tag on a nursery seedling should tell you the size of a mature eggplant for that cultivar. Harvesting eggplants when they’re small will give you better-tasting eggplants and will encourage the growth of more eggplants.
Harvest long, slender Japanese varieties when they are no larger than your finger or a hotdog.
You can also check ripeness by cutting into an eggplant. Seeds of a ripe eggplant should be a light yellow. If the seeds are brown, the eggplant is overripe and likely bitter.
The skin of purple varieties turns bronze when they are overripe. White eggplants will start turning yellow when overripe.
Harvesting and Storage Basics
Use pruning shears or a knife to cut an eggplant off the vine. Leave the green calyx attached to the stem end of the fruit.
To avoid the possibility of spreading plant disease, sterilize the blades of your shears or knife before and after cutting by soaking them for five minutes in a solution of 1 part 70 percent isopropyl alcohol to 1 part water. Let air dry.
Eggplants do not ripen off the vine and deteriorate rapidly, becoming spongy. Eat your eggplant as soon as possible after you pick it. You can store it overnight at room temperature. Eggplants will keep for about a week in a refrigerator at 45 to 50 degrees Fahrenheit.