Any thoughts on this ^^, or should I just stop fiddling with it and see what happens?
Just so you’re not confused by my wording later in this post, standard grape vocabulary in my part of the world uses laterals to refer only to the shoots that grow out of the leaf axils of the current year’s growth. What you’re calling laterals are just shoots. Or primary or fruiting shoots if you want.
To ripen fruit, you need at least 14-15 well-exposed leaves on the shoot. You get some compensation from neighboring shoots if they don’t have their own fruit, but I would not take too much growth for cuttings if you want fruit this year. The shoots you topped will send out laterals and keep growing eventually, but it may reduce fruitset.
On the plus side, topping the shoots on the upper cane will promote growth on the lower cane.
That is a good idea. I’ve read that it was pretty common to do this with greenhouse grapes in northern Europe.
I would not do a vertical cordon, nor try to keep the shoots growing off the cordon horizontal. The growth of the lower shoots will be severely inhibited by the upper shoots.
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Thanks. I was looking at this diagram in a book by Dr DG Hessayon, a UK botanist who’s written a huge number of succinct books on gardening.
I think his leader is your cane, his laterals are your summer shoots, his sub-laterals are your laterals?
It looks like I should leave well alone for now, and maybe post an update in Nov-Dec for advice on pruning, and maybe, flexibility allowing, poking that upper cane into the greenhouse.
The only thing in the meantime would be when I take cuttings - I only need one or two to plant in the polytunnel.
Update: the vine is looking quite neat and tidy, thanks to the advice above:
I’ve topped all the shoots at eaves height, and removed a few leaves to let the sun get at the grapes. Anything else to do now, or just leave it be?
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Looking ahead, there’s a convenient shoot which I might be able to train into the greenhouse. Is this the best thing to do, or should I try to feed one of the mature canes in? Long-term aim is to get rid of the outdoor part of the vine, except the main trunk. As you can see, it’s shading the tomatoes where it is now.
Yet another option: five or six of the cuttings I took a few months ago have rooted happily. It may be easiest to plant a couple behind the greenhouse (RHS in photo above) and train them inside, doing away with the outdoor vine altogether once they’ve become productive.
If it’s not a variety with resistance to powdery or downy mildew, you may need to spray.
As it is, that shoot is too weak to amount to much. You can try pruning that shoot to one or two buds this winter and see if it’s stronger next year.
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The vine has been pruned to two buds per shoot. It produced 14 bunches of green grapes, some reasonably sweet and plump, others not so much:
I just about managed to poke the upper shoot through a hole in the greenhouse, but it broke right at the last stage. Should I do any kind of repair, or leave it alone?
If it’s still well-connected on the bottom side, the shoot should recover. However, grapes don’t callus over and seal wounds the way most fruit trees do, so I would try to clean up the edges of the break if you can do it without causing further damage. You might want to look into painting the wound with a sealant or something to prevent infection as well.
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Thanks. Like a tree wound sealant (Arbrex) or maybe a grafting wax?
Either should be fine. You just want to keep the wound sealed for the next 3-6 months while it’s most susceptible to infection.
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