Grapes hold a fascination for many gardeners, who really like the idea of harvesting grapes from your own garden – there is something decadent and even Bacchanalian about it (Bacchus was the Roman god of grapes and drunkenness – to the ancient Greeks he was Dionysius.) When we look around, though, we see many enormous, rampant grape vines, and little or no fruit. The dream hasn’t come true.
So let’s get down to it and discover how to grow grape vines properly, and harvest those big bunches you can already see in your imagination. We are going to look at pruning of both eating and wine-making grapes, as well as a system that is suitable for grapes covering larger trellis and arbors.
Be warned, you probably never realized how boldly you have to prune grapes. Each year you will be removing about 90% of the growth of the previous year, so don’t be shocked by what you are going to read here.
Get Your Plants Off to the Right Start
Grape vines grow best in areas with cold winters and warm to hot summers. They need cold in winter, below 40 degrees for between 100 and 400 hours, depending on the variety. If you aren’t familiar with the concept of chilling hours, check out our blog on it. You will also need to know the number of hours needed for your particular varieties. If they don’t receive enough winter chill, plants won’t develop properly in spring. They also need a summer season with at least 5 months of frost-free weather, if you want successful growth and ripening.
Supporting Your Grape Vine
You need some kind of support to grow your grapes on. The simplest, and most common, is a strong wire stretched 30 to 36 inches above the ground. Use strong stakes and stretch the wire tightly across them. You can also use a double-wire system, with a second wire 30 inches above the first one. However in many areas people find that the more vigorous growth on the upper wire shades the growth on the lower one, so yields are not much greater with the double wires, except in very sunny zones. If you have more than one grape vine, space them between 4 feet and 8 feet apart. The wider spacing is good in areas with hot summers and good rainfall, on rich soil. The closer spacing is for areas with poorer soil and dry weather. If you aren’t sure, go with 6 feet apart.
The Goal of Pruning
Pruning a vine has two purposes. The first is to build and maintain a permanent trunk or framework of stems. This is a simple vertical stem with two or four horizontal branches along the wire(s), usually replaced each spring. Grapes flower and fruit only on new shoots produced from one-year old branches, so each year you will remove all the stems that have fruited, back to the framework, and grow a new crop. That is why so much growth needs removing – it sounds drastic but it isn’t.
How to Train Your New Grape Plant
You have checked you can grow grapes successfully, and bought suitable varieties. Now what? The chances are when your plants arrived they were growing in a pot, and it will probably be a cluster of branches. Unless it is early spring, and they have no leaves yet, it is probably best to just let the plant grow that first season.
The next spring, early, cut off all those branches, and leave only the single strongest stem, with its lowest three buds. That’s it – one twig and three buds. Let those buds sprout, and let your plant grow until the new shoots are almost a foot long. Now selected the strongest and straightest and tie it to a stake so it us growing upright. Remove all the other shoots. Through the season, tie it in to the stake as it grows, removing any other new shoots that form. Keep that stem straight and upright – it is going to be the permanent trunk of your grape vine, and the basis of everything else you do, so try to grow a really nice, straight one.
The Next Spring. . .
During late winter and early spring of the next year, take a look at your vine. Has it grown just a short distance above the wire? If that is all you see, then tie it to the wire and cut the top off, just above the wire. Has it grown a long way above the wire? Then tie it to the wire, cut it back to 5 buds and tie that piece to one side or the other of the wire. Does it have several strong side-shoots? Take the two closest to the wire, cut them back to no more than 5 buds, and tie one on either side, along the wire. If you have two wires, you may have enough shoots to do the same on the upper wire. If not, you will next year. Remove all the remaining lower side stems, and after tying it in, cut the main stem just above those remaining side shoots. New shoots from those horizontal stems should produce grapes.
The Next Spring, and Into the Future
The method of growing with just one wire is called Guyot pruning. With two wires, and 4 branches, it is called Kniffen, or 4-arm pruning. In both of these systems you will take out the previous year’s horizontals to the central trunk, and tie in the best two new ones you have, pruning them back to fit the wire. Also remove all other side branches, except of course for that main stem, which will get thick and gnarled after a few years.
Not recommended for Concorde grapes, but valuable with some other varieties, and also basically what you will do on an arbor, cordon pruning is a different approach. You will establish a permanent framework of a trunk and side branches along the wires, or to cover the space you have available on an arbor. Each spring cut back new growth to just a couple of buds. Soon, large clusters called spurs will develop. These will produce the flowering shoots. After a while you will see some branches and their spurs stop flowering. Cut the branch back to a strong new stem, tie it in and replace the old one. Repeat as needed.
Established vines can support upwards of 30 buds left after pruning, so growth can be prolific. As the vines grow through the season, the goal is to keep as many leaves as possible in full sun. that means removing weaker shoots so they don’t shade the stronger, fruit-bearing ones. It takes about 15 leaves in full sun to grow one bunch of grapes, so let that be your guide to what to leave or remove. Start this thinning early, in June, and reckon on spacing the new shoots 3 or 4 inches apart by removing surplus ones. Once you can see bunches of grapes, allow just one or two per shoot – remove any extra ones, or you will have a big crop of tiny, dry grapes. To get big dessert grapes, so growers use small scissors to remove smaller berries, opening up the bunch and allowing the remaining grapes to grow larger.
Later, shorten the stems back to 16 leaves, if they grow long, and tie them back to the wires to prevent breakage. Once the harvest season approaches you can remove the leaves around the clusters of grapes, to let more sun in to ripen them.
A Final Word
The secret with pruning grapes is to not worry. If you get it wrong, just cut them back and start again. They will understand. Growing grapes at home is supposed to be fun, not a source of anxiety, so relax and enjoy it – even if it sounds complicated when written down. It’s actually pretty simple and obvious once you get going.