Coastal Southern California, sunset zone 22, is generally not considered a good grape growing climate. Nevertheless, we have had success with a few grape varieties over the last decade and a half. Between my friend across the street and I, we have tried growing Black Monuka, Fantasy, Glendora, Niabell, Eastern Concord, Canadice, Flame, Perlette, and Jupiter. For seedless table grapes, my favorite has been Jupiter.
We don’t get enough annual heat or even a lot of sun during June and July. Our summers are dominated by what SoCal locals call “June Gloom” for a large part of the summer, with over cast skies until early afternoon, if the sun bothers to come out at all. Because of the mild weather, we are blessed to not need an air conditioner, but that also means successfully growing heat loving Thompson seedless, and most of the other popular table grapes found in the grocery stores, is completely out of the question.
About five years ago, I planted, on the recommendation of a member of California Rare Fruit Growers, to try Jupiter, a purple, seedless, semi-crisp grape. It produced a light crop after only 1 1/2 years in the ground, and I liked it so much, I planted a second one that same winter. Jupiter Grapes are ripe when they are a dark purple on the skin and green inside, with a crisp sweet taste. As far as my grapes go, Jupiter is the Goldielocks of grapes in the backyard. It is not too small, not too sweet, not to tart, it is just right.
So far, we have not had any diseases issues on this variety, including no powdery mildew, which often plagued my flame seedless most summers. Last summer we had very little sunshine, and it performed fabulously. It is a vigorous grower, which is much appreciated by the chickens who get many of the branch trimmings if the vines start to get out of control. Jupiter grape is a hybrid of American and European grapes, developed and patented by University of Arkansas in 1998.
Jupiter is normally the second grape variety to ripen at my house, just a few days to a week or two behind Canadice. This year we picked our first few clusters on July 1st. Most of the Jupiter grapes should be ready within the next few weeks. Right now, some berries are still reddish. I am aware that other parts of the country don’t start picking these until much later in the summer.
My second Jupiter grape vine isn’t planted in the best location, and only gets half day sun, at the very best. Never the less, it still flowers and produces just fine, just slightly later than the one near the veggie garden. It actually works out well for us, helping to stretch out our harvest. If I could only pick one seedless table grape variety for coastal Southern California or similar cool climate, it would be Jupiter.