The botanical gift that keeps on giving, grape vines provide you with fresh, delicious fruit year after year. The secret to producing the most plentiful harvests: pruning. Skipping out on this step can prevent your vines from getting all the sunlight they need, which inhibits growth. If you're new to pruning grape vines, don't stress—it's a simple process you only have to tackle on an annual basis. Becoming familiar with the anatomy of a vine is the first step. Then, all you need is your trellis, a cutting tool, and your best gardening judgment. The benefits (i.e. all the homemade wine, jams, juice, etc.) are definitely worth it.
Grape Vine Terms to Know
Before you touch any of your grape vines, make sure you know the essential terminology. Here are the parts of the plant to add to your gardening vocabulary:
- Trunk: Old wood that grows vertically
- Cordon: Old wood that grows horizontally on the trellis
- Arms: Old wood coming off the cordon
- Shoots: Green shoots that began growing in the current season
- Canes: ~1 year-old wood that was a green shoot in the previous year, also where buds grow
- Buds: Fruitful shoots that grow on canes
Understanding these terms makes it easier to break down the grape vine pruning process. Check out a few diagrams or photos online, such as the ones from the California Table Grape Commission.
Why You Need to Prune Grape Vines
To put it simply, pruning grape vines allows the plants to get enough sun. If you let your vines grow freely, shoots and clusters will overwhelm the plant and create barriers that block the light. It's also important to get rid of older, less healthy canes and old wood to promote new growth and avoid diseases.
"We're trying to manage where the sun is and where the fruit is," says Randall Vos, commercial fruit crops field specialist at Iowa State University. "[Without pruning], the clusters aren't going to set as many berries as you'd want because there are too many, and it's going to be a big shady mess."
A grape vine is a perennial plant, meaning it comes back each year. Not cutting back the shoots to limit the amount of fruit a vine produces may give you a higher yield in your first year, but it hurts your plant in the long run, Vos says.
Tips for Pruning Grapes
Pruning should be done each year during the winter or dormant season, depending on where you live (generally between January through March). Fall is too early—even if plants look like they're dormant, they're still producing sugar and nutrients, Vos explains. To prepare for pruning, use the summer season to teach your vines to grow vertically on your training system (a trellis, arbor, or posts). To cut your canes, invest in a pair of handheld pruners or loppers. Stay away from saws (especially chainsaws).
The buds on a grape vine produce a lot of fruit, but you don't need to keep all of them to have a full crop. Each dormant season when it's time to prune, choose a few of the strongest canes to leave and cut back the rest. "Usually people choose 10 to 12 good canes and shorten them to four or five buds each," Vos explains.
When deciding on the canes to keep, look for smooth bark and a dark color. The darker the color, the more cold-hardy the stem tends to be. Longer canes give you bigger clusters, so if you're growing table grapes and want that standard, store-bought size, you may consider pruning off the shorter ones.
Grape Vine Pruning Mistakes to Avoid
The most common mistake home growers make? They don't clear out enough canes, Vos says. If the thought of aggressively chopping back your grape vines causes you slight panic, just remember pruning means prosperity. It might seem contradictory, but the more growth you remove, the healthier your remaining vines will be.
"If you leave 40 to 50 buds on an average-size grape vine when it's full grown, you're doing pretty good," Vos says. "You can get complicated with pruning formulas, but if you have a vigorous vine that's four to five years old, 40 to 50 buds should be a guesstimation to make it work out."
Another misconception to watch out for involves the size of the cane: Remember that bigger isn't better. Moderate-diameter canes yield the best results. Think slightly thicker than your thumb, and definitely not any smaller than a pencil.