Pruning vs. Training?

A long time ago, when I first started growing fruit trees and vines, I read a lot about the all-important pruning and training they require. But I couldn’t get clear on my head what exactly the difference was between “pruning” and “training.” I went on to learn that and a whole lot more about pruning (through books, as an ag researcher for Cornell University, and with practical experience), and eventually wrote my own book about pruning, hoping to present the techniques with more clarity and completeness than all the books I had read. Perhaps my book, The Pruning Book, does that.
Grape vine in spring
Okay, to answer my question of yore. “Training” is developing the young plant to a permanent framework that is sturdy and will always have its limbs bathed in light and air, and whose fruits hang within easy reach.

Kiwifruit within easy reach

Kiwifruit within easy reach

Training involves some pruning as well as coaxing stems to grow in certain directions. Once a fruit tree or vine’s training period ends, it generally only needs annual pruning.

Vine-y Training

I thought of all this today as I pruned hardy kiwifruit and grape vines. Both fruiting vines have been trained and are pruned similarly, with one slight variation that I’ll soon mention.

The kiwi and grape vines are trained as “double cordons” which are permanent arms sitting atop a trunk. They run in opposite directions along the middle wire of a 5-wire trellis, the wires parallel and supported about 6 feet of the ground on the cross-arms of T-posts. Each young vine was planted next to a metal or wooden stake to which the plant’s most vigorous stem was tied.

Once that trunk-to-be reached up to the middle wire, I tied it there and cut off all other stems. That trunk-to-be does, of course, keep growing; that new growth gets bent over and tied along the middle wire. Bending coaxes new buds to burst just beneath the bend, one of which is also bent over and trained along the middle wire in opposite direction to the first stem. Both these horizontal stems became the cordons, permanent arms of the plant. Growing off at right angles to the cordons are the fruiting shoots which, weighed down with their weight of fruit, drape onto the other wires.

Vine Maintenance

Today I’m maintenance pruning vines whose training period ended years ago. Maintenance pruning a mature fruiting vine keeps it bearing high quality fruit within easy reach year after year, all accomplished with a renewal method. That is, except for the trunk and the cordon, the vine is completely renewed with each year’s pruning.

I’ll admit it: A vine looks like a tangled mess before being pruned. But step by step, it  begins to take shape and make sense. Kiwi before pruning

Knowing how a plant bears fruit is important in maintenance pruning. Kiwi and grape vines bear on new shoots growing off one-year-old stems. Kiwis bear best if those one-year-old stems are about 18 inches long. Grape one-year-old stems can be left long or short, but for my method of training, I want each one about two buds long, which is just a few inches.

Fruiting grape shoots emerge from 1-yr-old stem

Fruiting grape shoots emerge from 1-yr-old stem

Step one is a no-brainer. The outermost wires are 4 feet apart so I lop all growth back to just beyond those wires. My tool of choice for this is a battery-powered hedge trimmer although pruning shears would also do the trick, except at a snail’s pace.First step in pruning

Step two is to remove excess growth, which does two things. It removes potential fruits so that more of the plant’s flavor-rich goodness gets funneled into those that remain, and it decongests the plant. For this step, I cut back all stems 2 years or older.

But wait! Two-year-old stems have one-year-old stems, the stems needed for bearing shoots, growing off of them. So rather than cut a two-year-old stem all the way back to its cordon, I cut it back to a one-year-old stem originating near the cordon. Some one-year-old stems also grow right from the cordon. The best one-year-old stems are those that are moderately vigorous and, of course, look healthy. Moderately vigorous stems, for grape or kiwi, are about pencil thick (if you can remember what a pencil looks like; if not, about 1/4” thick).

Kiwi stem and pruning detail

Kiwi stem and pruning detail

There will always be too many one-year-old stems for the plant to make tasty fruit. So I reduce the number of potential fruits by removing some of the one-year-old stems, enough to leave six to ten inches between them on each side of a cordon.

Pruned grapevine

Pruned grape vine

Pruned kiwi

Not finished yet. The final step is to shorten the fruiting shoots. For hardy kiwis, I cut them back to 18 to 24 inches long. For grapes, to about 2 buds or a few inches long.

Oh, one more thing to do: I prune off any new growth rising up from ground level or along the trunk lower than the cordons.

And one more thing: I step back to admire my handiwork. (Here is a video of me pruning a kiwi vine.)  

But What About Bushes?

You might have noticed, early on, that I wrote about pruning and training “fruit trees and vines.” What about blueberries, currants, gooseberries, elderberries, and other FRUITING BUSHES. Yes, they need annual pruning also. No, they do not need training. Although the plants are perennial, their stems are evanescent, all with a limited life. They are pruned by a renewal method — at ground level. All this and much, much more (pruning ornamental plants, houseplants; creating and caring for an espalier; how to scythe; etc) in The Pruning Book, of course.

Pruning, Not Too Late

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Time is running out to finish pruning my kiwi and grape vines, apple, pear, cornelian cherry, filbert, and chestnut trees, rose, gooseberry, currant, blueberry, raspberry, blackberry, yew, and fothergilla bushes . . . now that I list most of them, it doesn’t really seem like too, too much still to prune. Some people worry that it’s too late to prune. Nope. Most pruning is done during the dormant season, that is, anytime plants are not growing or, if deciduous, leafless. (A notable exception is spring-blooming shrubs, which are best pruned right AFTER they finish flowering. For more on all aspects of pruning, see my book, THE PRUNING BOOK.)
Kiwi, before pruning
I’ll usually do a little pruning in autumn, after leaves fall, but mostly I’ll be grabbing pruning shears, loppers, and saw as I go out the back door in late February or March, after the coldest part of winter is over. Waiting is most important with plants that are least cold-hardy because these plants tolerate cold better if left alone and, by waiting, I can see what has been damaged during winter. Buds on damaged stems aren’t swelling up this time of year so those stems can be cut off.

A few plants warrant dragging out that waiting period even longer, until they are in bloom, which is when they heal quickest. Peaches are prone to infections at wounds, pruning or otherwise, making these trees good candidates for waiting.

Kiwi, after pruning

I may also wait to prune my grape vines until new shoot growth is underway because then they are less likely to bleed sap.
Bleeding sap worries many gardeners. Isn’t the plant suffering from that gaping wound oozing a watery fluid? No, bleeding does no harm to grape vines. But some of my grapevines climb along the arbor over my patio. It’s very pleasant to sit outdoors on that patio on warm, spring days; it’s very unpleasant to sit there with sap dripping on my head.
Kiwi vines also bleed. No matter. My kiwi vines climb a strictly functional trellis below which we don’t sit.
Root pressure of water being forced up the vines is what makes grape and kiwi vines bleed. Once leaves unfold, they take up that pressure and bleeding ceases.
Bleeding is most welcome from maple trees. What comes out this time of year is a dilute, sugary sap that, when boiled down to concentrate the sugars, yields maple syrup and, if boiled down still more, maple sugar. Sugar concentration in the sap can vary, depending on such factors as temperatures, age of tree, site, soil fertility, and moisture. Typically, the ratio of sap to finished syrup is 40 to 1.
It’s not root pressure that’s forcing sap out the spiles I’ve tapped into holes bored into two sugar maples. Maple sap runs best when temperatures fluctuate between 20-something degree nights and 40-something degree days. Cooling temperatures cause gas bubbles in the trees xylem cells (the inner ring of trees’ cells in which liquid is conducted upwards from the roots) to shrink and to dissolve. Something’s got to fill that newfound space, so more liquid is sucked up from the roots and into the cells. As temperatures drop further, ice forms and gases are locked within the developing ice.

Come morning, pressure builds in the cells as rising temperatures melt the ice and release the gases, forcing liquid out any holes in the bark. That liquid makes its way out the spiles, thence to buckets hanging beneath the stiles, and finally to a large pot that sits and steams on my woodstove through February and March. When the sap reaches 67% sugar, boils at 219° F., or tastes like maple syrup, it’s ready to be bottled up. For me, this has been a good year, with over 5 quarts of syrup already from only 4 taps.
Only a few trees can be tapped for their sap. Any maple can, as can black walnut and butternut. Each yields a syrup with a different flavor. Birch trees also release a sap that can be boiled down to make a tasty syrup; in this case, though, it is root pressure, as with grapes, that forces out the sap.