David Handley: I'm David Handley, vegetable and small fruit specialist with the University
of Maine Cooperative Extension.
Today we're going to be talking about a simple system for pruning hardy grapes here in Maine.
The pruning system I like to use is very simple.
It keeps the plant open, so it gets light in the summer time, but it also protects the
plant a little bit in the winter.
This system works best with concord type or labrusca type grapes, which are the grapes
that tend to grow best in Maine.
There's really a couple of systems that will work well for labrusca type grapes.
The first one I want to talk about is the four arm kniffin, and that's what we're going
to prune first.
The four arm kniffin consists of a perennial trunk, which goes from the ground right up
to a top wire, which is set at about five feet.
Coming off of this trunk, we will have four arms, or canes, one-year old growth.
Two on the top wire, running each side of the top wire, and two on a lower wire.
This lower wire should be set at about two and a half feet off the ground.
Every year, we're going to come in and prune it so we continue to have a perennial trunk,
but only four one year-old trunks to produce the fruit.
Here is our permanent trunk.
You can see here, this is a cane from last year.
Two year-old cane, this was our fruiting cane last summer, and you can see the difference.
Here's this year's cane, that nice chocolate brown color and smooth bark, and here we go
with the older cane, the two year-old cane.
The bark is starting to peel, and has more of a gray look to it, so we know that this
particular shoot isn't going to fruit again.
It's the one year-old shoots that come off it that will fruit.
This is going to get pruned out, so that we can keep our fruiting wood closer to the trunk.
We'll just take that back to a good fruiting shoot, and we'll start to cut it out.
This is where it gets fun.
We need to wrestle this out of the trellis, and of course, all these little tendrils have
tied it up and around most of the growth that's there.
It takes a little bit of cutting, but be careful not to break the fruiting canes that you want
to leave behind.
Pull it off, and that will open the planting up so we can see what we have left for good
fruiting wood for this year.
We've taken off the four fruiting canes that we left last year, and you can see pretty
much all that's left, at this point, is the green shoots from last year, that will provide
us with good fruit for this year.
Now we need to choose which four we want to put up.
We're going to have four canes.
One, two, three, four.
Two for the lower wire, two for the upper wire, each heading off in different directions.
What I want to look for in this case is cane that's got this nice chocolate brown color,
and is about 3/8 of an inch in diameter.
About the width of your little finger.
If it's thinner than that, if it's very weak, it won't produce good fruit.
Thin stuff like this, less than 3/8 of an inch in diameter, we'll just cut that right
out.
Here we've got one that's going to go in this direction, that looks very nice.
I'm going to count, remember we want about 10 buds on it, so we'll count our buds.
One, two, three, four, five, six, seven, eight, nine, 10.
Then I just cut out beyond that, because the weaker stuff at the very end isn't going to
produce very good fruit.
I have my four arms, but you can see I still have some leftover canes.
What I'm going to use these for are what we call "renewal spurs."
I'm going to cut these back so that they just have one or two buds on them.
What I'm going to use these buds for, the green shoots that will emerge from these buds
and grow out, will be the canes that I'll be putting on the wire next year for fruiting.
We call these "renewal spurs."
I need fruiting canes and I need renewal spurs.
I need at least one renewal spur for every fruiting cane that I'm leaving behind.
Here in the north, I cheat a little bit.
I tend to leave a little extra fruiting spurs on there, just in case we have some winter
injury, I may need some more cane to choose from.
I've got my lower one, so I don't need these two, although they're pretty good-looking
wood, actually.
That means that, as renewal spurs, they'll do just what I want them to do.
I don't need, but we want that bud, leave that bud for a renewal spur.
As you can see, we finish up with my permanent trunk going to the top wire, and here I have
my four fruiting canes 3/8 of an inch thick, looking good, and each of these canes is cut
back to about 10 buds.
For each cane that I leave spread out like this, I also leave one or two renewal spurs.
The shoots that come from these buds will be the canes that I put up on the wire next
year.
Pruning should take place every year.
We usually do this in the dormant season.
Any time from January, right up through March, until these buds start to swell up, is the
time to get your pruning done.
Anything you prune off of this should be taken out of here, chopped up and composted, brought
to the burn pile, or just kept out of the planting, because it is a potential source
of diseases for next year.
It looks difficult, but it's really not that hard to prune your grapes.
This will guarantee us a good crop every year, if the winter is kind to us.