Native to the southeastern United States, muscadine grapes do grow throughout southern California including San Diego, though they aren't as common as other types of grapevine. Muscadine grape varieties include Black Beauty, Black Fry and Sweet Jenny. The fruit ripens from September to October and can be eaten fresh, cooked into jam or juiced. San Diego gardeners should obtain 1-year-old muscadine grapevine plants in the spring.
Test your yard's soil using a pH test kit. Muscadine grapes prefer a soil pH of 5.5 to 6.5. Most San Diego soils are slightly alkaline since the city's water is alkaline. Lower your soil's pH if necessary, using sulfur.
Dig a hole twice the size of your grapevine's root ball. Plant the vine along a fence so it has a natural trellis, or plan to erect your own trellis to support it. Remove stones and weeds from the hole before planting your grapevine.
Pull your grapevine from its container. Squeeze the root ball between your hands to loosen it roots. Place the plant in the prepared hole so it rests at the same depth as it was planted in the container. Holding the plant vertically straight, fill the hole with soil to plant your grapevine.
Water the newly planted muscadine grape until the soil becomes saturated. Thereafter, provide the plant with 1 inch of water per week unless you receive adequate rainfall.
Fertilize the muscadine grape with 1/2 lb. of 10-10-10 fertilizer just after planting. Fertilize again the first year with 1/8 lb. ammonium nitrate in May and late June. To apply the fertilizer, scatter it along the soil near the grapevine then water the plant until the ground becomes saturated, to work the nutrients into the soil.
Double these fertilizer amount in the second year. In subsequent years, apply 2 to 4 lbs. of 10-10-10 fertilizer in March and 1/2 lb. ammonium nitrate in June.
Grow the grapevine along the fence the first year.
Prune the grapevine in early spring the year after planting. Cut back the previous year's growth to a height of 4 to 5 inches. Remove suckers growing along the base of the vine. Cut back the height of the main vine so it is equal to the height of your fence post. Then allow the vine to grow for the second year and prune again in the same manner to continually thin out the prior season's growth to promote the development of new fruiting wood. Remove dead vines that turn tan or black, as well as damaged, bent or broken shoots.
Check for insects pests that eat grapes or damage the leaves. If you see holes in your leaves, discoloration or other spotting, contact the San Diego County Master Gardeners for help (see Resources). As California Rare Fruit Growers organization notes, muscadine grapes in California should not experience disease, though insect pests and birds may be a problem.