Growing different sorts of grapes (Vitis spp.) On the same trellis is potential if all of them have the same ecological conditions, but not all kinds do well together. Varieties like “Thompson Seedless” (Vitis vinifera “Thompson Seedless”), hardy in U.S. Department of Agriculture plant hardiness zones 7 through 9, “Concord” (Vitis labrusca “Concord,” USDA zones 5 through 9) and muscadine (Vitis rotundifolia Michx., USDA zones 6 through 10) have weather conditions which are too varied to enable them to be implanted together. Plus, one number can interfere with another one’s growth.
Grapes with seedless fruits actually begin to grow tiny seeds, but those seeds don’t develop correctly and stay unnoticeable in the fruits. This process is called stenospermocarpy and affects only seed growth; it does not have an effect on pollination requirements. So make sure your seedless grapevines are pollinated in order for them to make fruits. Therein lies a problem, but if you would like to plant varieties like “Thompson Seedless” next to other types of grapes. If those other strawberries create hydrogenated fruits — as do classic “Concord” and muscadine grapes, then pollen from the seeded grape varieties might end up pollinating the seedless varieties. The end outcome could be seeded fruits on vines which should produce seedless fruits. The seeds will likely be tiny but annoying if you weren’t going to own them.
Enough Space and Seedless Varieties
A seedless variety needs at least 75 feet of buffer zone to prevent accidental cross-pollination using a seeded kind. That distance would require a lengthy trellis for a home garden. An option is to plant only different seedless varieties on your trellis. Although “Concord” has seeded fruits, the cultivar “Seedless Concord” (Vitis labrusca “Seedless Concord,” USDA zones 4 through 9) doesn’t, and therefore it is a seedless choice. With it, however, may enable you to run up against another problem in the event that you also develop “Thompson Seedless.” That’s because “Seedless Concord” was created from “Concord” so has some of its own attributes, and “Concord” doesn’t develop well in all the very same locations or distances as “Thompson Seedless,” in accordance with a “Los Angeles Times” article.
Hybrids since Substitutes
One more choice that could get one three varieties on one trellis — if you can offer enough space for all three to develop — would be to substitute a hybrid for one of the varieties. “Thomcord” ( Vitis vinifera x Vitis labrusca, USDA zones 5 through 9), by way of instance, is a hybrid “Thompson Seedless” and “Concord.” Its fruits are seedless, and therefore it would not affect a “Thompson Seedless” grapevine’s pollination, and “Thomcord” and “Thompson Seedless” have similar climate conditions. So provided that you could provide that 75-foot buffer to isolate muscadine, which produces seeded fruits, in the seedless varieties, you could fit those three types on one trellis.
Muscadine should develop well in some of the same places as “Thompson Seedless.” Muscadine requires more humidity than is present in many inland desert areas and more heat than is present in some coastal areas, according to the California Rare Fruit Growers website, but the variety does OK in some warm grape-growing areas Such circumstances can be very hit and miss in Mediterranean climates, but, especially if a particular area has a lot of microclimates. If you’re able to get a place in your lawn which mimics the hotter areas where “Thompson Seedless” grows but supplies more humidity than you could find in a lot of Mediterranean-climate locations, then you might have a prosperous muscadine harvest.