Grapevine help

[Sonja]

Hi, we have been lucky enough to get our hands on some mature Shiraz grapevines. The only problem is the main stem/trunk is too tall for where we want to put them. Does anyone know if we can trim
the trunk down to approx 500mm off the ground? Will new branches/stalks grow still?

[ameno]

You can trim the trunk if it is thick and old enough, and it will grow new buds from under the bark. If the vine isn't old enough, though, it won't resprout and will die. You also need to make sure to leave a decent length of trunk (at least 6 inches) above the graft union (a bulge in the trunk a little way above ground level).

It's probably best not to do something so drastic, however, and this is not the time of year for hard pruning, anyway. How tall are the plants now, and why do you need them so short?

[Sonja]

Hi Ameno, thanks for your reply. The vines are about 10 years old with trunks at a height of about 1.5m with no branches below that height. We want them to hide a fence line on our small farm, but we also have really gorgeous views over the fence line so if they are too high they will block out the view but not the fence 🙈. The trunks are thick and very mature looking. I’m in Australia so it’s winter over here. Our vines are totally dormant right now 😊

[ameno]

If you're in Australia then I worry that mid July may actually be a bit too late. Sap starts to rise very early in vines, and they bleed profusely if you prune them from late winter until mid spring.
Try cutting off a thinner branch (around pencil thickness, or maybe slightly more) as a tester and monitor it to see how much it bleeds over the following 24 hours. If it's little to none then it should be safe to perform your desired more drastic beheading. If it bleeds quite a lot then it's now too late and you had best wait until next winter to do it, and do it a bit earlier (before midwinter, to be on the safe side).

Although one final question: how tall is this fence you want to hide? Vines can easily be trained pretty much entirely horizontally, or even downwards, so a vine with a dormant trunk height of 1.5m can easily be kept under about 1.7m even during the height of the growing season, as long as you tie in the new growth horizontally and prune any side shoots over the course of the summer.
My grape vines are trained along wires about 1.5m off the ground, and every winter I just cut them back to the main framework about level with the top of the wires, then as they grow over the summer I tie in all the new growth horizontally or else just cut it off (grapes need heavy summer pruning, anyway, or else they very quickly become and overgrown rampant mess).
So depending how tall the fence is, you may not need to cut them back at all. And at the very least, I think cutting them down to 50cm is probably too much.

[Plot70]

I would just plant them at an angle to loose some of the height.

[ameno]

^That's also a good idea.

[Sonja]

Hi, the fence is 1.2 high so we ideally wouldn’t want the wires to be over 1.1 to be safe. That’s a good point about the bleeding, we will be sure to check that first and wait if we have to.
What do you think would be a safe cut?
Thanks for all your advice ☺️

[Jungle Jane]

Looks like a vineyard near me,all the vines are this height & wires keep the height low. They’re at this height for a reason. Who owns all those vines they would be able to help,they’ll be experts at this or are they not about if it’s winter there?

[ameno]

Hi, the fence is 1.2 high so we ideally wouldn’t want the wires to be over 1.1 to be safe. That’s a good point about the bleeding, we will be sure to check that first and wait if we have to.
What do you think would be a safe cut?
Thanks for all your advice ☺️

I think personally I would do all I could to avoid having to prune them too drastically. If you plant them at 45 degrees instead of vertical, as Plot70 suggested, they would probably be short enough. You could also plant them deeper than they were originally (as long as the graft union remains above the soil surface) to lose a bit more height.

[Sonja]

Ohh that’s an interesting idea.. I could definitely go a little deeper then. How can we be sure what the graft union is? Or if they have one at all?

[Sonja]

We need to be careful not to block out the view

[Sonja]

[Nicos]

Really lovely views Sonja - can’t blame you for wanting to preserve them.
Out of interest ( cos I’m nosey - well - so too are the rest of the Grapes to be honest ) ….what part of Australia are you in?

[ameno]

Ohh that’s an interesting idea.. I could definitely go a little deeper then. How can we be sure what the graft union is? Or if they have one at all?

It ought to be a fairly obvious bulge in the trunk 10-20cm from the ground. Sometimes the bark will look a bit different above compared to below.
You could try asking the original owner if they are actually grafted. Most grapes grown commercially are, but not always (unlike fruit trees, grafting does not cause dwarfing in the plant. Grapes are grafted merely to give more resistance to soil diseases). I can't seem to see any graft unions in that picture you posted, so they might not be grafted, in which case you can plant them as deep as you like (within reason).

[Sonja]

Haha thanks Nicos, we do love it. Little piece of paradise for us. The farm is in Yallingup Western Australia.