Gardeners welcome a good challenge, and growing high-quality grapes in a home garden setting is no small adventure. Beyond simply choosing the correct grape for local conditions and the correct type for the application you have in mind, you must know which grapes are self-fertile. Most garden-variety bunching grapes do not require a pollinator, but will benefit from the extra help at pollination time. Muscadines, however, must have a pollinator to set fruit.
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Self-Pollinating vs Self-Fruitful
Before selecting a grape variety, it is important to understand the differences between self-pollinating and self-fruitful varieties. While these two terms may sound interchangeable, you will be terribly disappointed if you do. Self-pollinating fruits can set fruit with only other plants of their own kind to pollinate them. So, if you plant Concord grapes, for example, plant two or three and they will pollinate one another. Self-fruitful plants can theoretically pollinate themselves, even if there is only one plant around. In a small garden setting, self-fruitful plants can save a lot of space.
Muscadines Require Pollinators
Muscadine grapes are a special case among home grown grapes. In most cases, they require an additional variety to pollinate them. Many muscadines, such as Scuppernong, require cross-pollination. These plants carry only one sex per plant and thus require male flowers to produce fruit. Plant Carlos, Magnolia or Dearing within 25 feet of female muscadine grapes to provide cross-pollination.
Bunching grapes, for the most part, are self-pollinating. You can plant two or three vines of one variety and they will pollinate each other and set fruit. Some gardeners plant different varieties simply to extend the harvest, but if there is a single variety that you prefer, it can be planted alone. Grapes are not self-fruitful, however, so always plant in pairs at minimum.
Once you've got your grapes established and proper pollination is set up, it's important to know how to tell if the fruit is ripe. Usually you will be able to harvest your first grapes in the second or third year of growth. Grapes are not always ripe when the fruit's color changes, unlike a lot of other fruit plants. Check fruits for softness instead of relying on color, sample one or two grapes if necessary. Grapes do not continue to develop sugars after cutting, so you must be absolutely sure that they are ripe before harvest.