Because seeds from grapevines (Vitis spp.) don’t produce plants like the mother plants, the seeds usually are sown only by plant breeders in search of new grape varieties. You, too, can create your own cultivar in that way, though it may be inferior to its mother plant. Because the hardiness of grapevines ranges from U.S. Department of Agriculture plant hardiness zones 4 through 10, depending on the variety, select seeds from a type that flourishes in your climate. Some seedlings may produce fruits within two years while others could require up to seven years of growth before they begin producing.
Harvest grape seeds from fruits that are fully ripe by slicing them in half lengthwise. Extract the seeds with the tip of a clean knife or your fingernails, being careful not to harm the seeds in the process. After dropping the seeds into a container of water, allow them to soak for 24 hours, skimming off and discarding all of them that don’t sink.
Drain the remaining seeds the following day, and place them inside a small container accompanied by a little damp peat moss. One tablespoon of peat moss should be adequate for up to 50 seeds. After capping the container, leave it in a 35- to 40-degrees Fahrenheit refrigerator for three months. The exposure to cold is called the stratification period.
At the end of that time period, open the container and plant the seeds at a depth about three times their length in a flat of damp and sterile seed-starting mix. Ensure the flat has bottom drainage holes, and space the seeds 1 1/2 inches apart from each other. Place the flat under a grow light that runs for 16 hours per day because grape seeds germinate best under long-day conditions, and keep the seed-starting mix damp. If the temperature remains at about 70 F during the day, preferably dropping to 60 F at night, some seeds may germinate, or sprout, within two weeks, though others may take two months or longer to sprout.
Reportedly, placing grape seeds in running water eliminates their stratification period requirement because the water washes away their germination inhibitors. Try that technique by inserting damp grape seeds in a small, muslin bag immediately after you harvest the seeds, and place that bag in running water, such as in a “babbling” brook. Tying the bag to a stake may be necessary to prevent the bag from being swept away.
Under those conditions, the seeds can begin to make roots in eight days, after which they should be planted in the same way you would sow stratified seeds that have no roots. Don’t leave the seeds in the water longer than 12 days, or their roots will begin to turn brown.
When the little grapevine seedlings have two sets of leaves, transplant each plant into its own 4-inch-diameter pot filled with a mixture that is 8 parts potting soil, 1 part pumice and 1 part sand. If you like, you can feed them with a plant food recommended for seedlings -- such as 2-3-1-- at one-half the fertilizer package's recommended strength. For the first month, mix 1 tablespoon of 2-3-1 fertilizer with 1 gallon of water. Afterward, raise the fertilizer amount to 2 tablespoons per 1 gallon of water. Transplant each seedling into its own 1-gallon pot about six weeks after each seedling was moved into the 4-inch-diameter pots.
The young grapevines should be ready to go outdoors when each plant has added six true leaves to its original two leaves, which are seed leaves. Accustom the vines to outdoor conditions by setting their pots in a shady position for a few hours every day at first and then taking them back indoors for the rest of each day. Gradually shift them into more sunlight.
After your location's last average spring frost date, select a position for the grapevines, ensuring the site has full-sun exposure and moderately rich, well-drained soil and is beside an arbor, trellis or fence. Plant the seedlings about 8 to 10 feet apart, making each planting hole wider and deeper than its respective vine's root ball and situating the vines at the same soil depth at which they grew in their pots. Fill the remainder of the holes with the soil you removed to make the holes; ensure the soil around the plants is level with the surrounding ground. Cut each grapevine back to its lowest two leaf buds. Water the plants' soil well, and ensure that they receive at least 1 inch of water per week during their first year.
Work a small amount of balanced fertilizer – about one-fourth of the regular rate – into the soil around each vine. For example, use 5-5-5 organic fertilizer, applying about 3/16 cup every other month from spring through autumn. Increase the fertilizer amount by one-fourth each spring until the grapevines receive the fertilizer package's full recommended amount per feeding – such as 3/4 cup of 5-5-5 organic fertilizer -- in their fourth year.