Optimal grapevine length?

Hello all

Im in maybe zone 9a/b in Japan. I have a Pione vine I got 2 years ago that produced 2 very nice bunches last year. This year I’ve added a Kyoho and Seto Giants. These are all large table grapes grown locally.

I find a lot of the information on pruning a little confusing and my trellises are not exactly standard. My trellis is about 4/5 feet off the ground and running horizontally. The plot is triangular, roughly 15 x 10’. Each vine will have approximately 7 foot sided triangle for itself.

My main question here is how far should I let the vine grow for optimal fruit? I’ll have to keep them trimmed down to stay with in this triangle. Will that retard the size of the mature vine and amount of fruit? or does it make no difference how small I keep the canopy and the trunk will just keep getting thicker and thicker producing more and more fruit bunches over the years ?

There’s a large patch of barren ground to the left passed my Peachtree where I could string the vines out over more trelliswork if it’s advantageous. From there they can string out as long as they want, as the ground isn’t good for growing much but the area gets full sun all day.

Thanks so much.

Allowable fruit load is proportional to the amount of sunlight intercepted by foliage. So the more you let the vines spread out the more fruit you can leave. Once the canopy reaches full size the yield potential is at a maximum. Yield won’t increase after that no matter how big the trunk gets.

Most grapes set too much fruit and a lot needs to be thinned out. Or one can prune more so as to leave less buds on last yrs wood. That will reduce crop load.

Thanks for the reply.
So, as I want more fruit, I could for example extend the trellis out 30 feet to the left. Trim the three vines so that all three run parallel to each other separated by maybe 2 or 3 feet each, but running out 30 feet long. Each vine could then have grapes for example at 3 feet intervals. So 10 bunches per vine, a total of 30 bunches between the three vines.
Does this sound reasonable?

Yes spreading the canes over a larger trellis will increase yield. And I’d think you could expect more than 10 bunches per vine.

The tricky part will be pruning. You can cane or spur prune as you spread out. For either there would be permanent wood and last years wood which bares the fruit. With experience the pruning becomes easy.

I’ll have to research those cane and spur techniques more exactly to be successful in their application.
Last month I already pruned the grapevines. One of the canes had extended out about 15 feet in one season and I cut it in half. I guess that wasn’t the right thing to do if I’m trying to extend the vine out over a new trellis. I should select only one cane and let it grow and chop all the side ones off?
As a side, If a single grapevine can extend so far and produce so much, why do commercial vinyards plant them much closer together and trim them down?

They get to full production sooner with closer spacing. If a plant dies there is less loss. And I’m sure there are other reasons involving pruning and possibly fruit quality.

I edited my above post while you were replying. Thanks.

I saw your post on another site and hesitated to respond. At any rate, welcome aboard!

Pione grapes are not a variety that we generally work with here (for whatever reason), but are said to be excellent and common in Japan.

My ‘Crimson Seedless’ grapevine, a common and excellent table grape here that harvests in the Fall window, is one of the few things that I try to force into submission. I give it a designated two wire trellis of 8’, in the most blast-furnace-hot part of my lot, and I instinctively (improperly and stubbornly) spur prune it. My plan basically leverages the vine’s will to live and fruit. :slight_smile:

So I think grapevine requirements are somewhat variable and flexible. I would start with at least a minimum 8’ run, plenty of sun and one of the well documented pruning methods. There are two types of pruning and you’ll need to discover which is correct for your variety (even that is flexible). Here are some easy to follow videos for each type of pruning:

Here’s my vine leafed out last year:

Here’s a nice bunch of tasty ‘Crimson Seedless’ grapes:


Thanks Clint, nice looking grapes.

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Even though I’m spur pruning the vine, you can see that I get plenty of grape flowers forming at the new sprout tips:

I watched those two videos and they’re pretty helpful. By the way, here’s some of the grapes I’m talking about from last year:

I ended up being able to harvest those two bunches in September and they were really good.

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How about suboptimal lengths? I plan to grow some grapes up the posts of my back porch, which means they’ll need to climb about 7-8 feet before I let them branch sideways. Does anybody see this causing problems for me long-term, beyond being less efficient?

Looks like nobody’s going to bite, so I’ll tell you the only thing I know. Tried to grow a vine in low light to the full sun roof, gave up as the 10 feet was only half crossed after 1 year. I’m sure there’s a formula for vine length and efficient fruit growth.

I don’t think it should matter so long as there are enough leaves and light for the clusters to ripen. In wine grape growing there are a lot of different trellis styles and pruning styles. Some have a short trunk and then have the fruiting canes about 3 feet off the ground with all the shoots and leaves growing up. Others do the opposite and have a much longer trunk and have the grape clusters up a the top with the shoots and leaves hanging down below.

Here in Virginia, where the wine growing industry is relatively young, the cutting edge guys have been experimenting with vine spacing, row spacing, trellis and pruning styles, etc and a lot of what was standard practice 20 years ago (based on California or France) has been scrapped and updated based on experimentation and lessons learned. I say all of that as an intro to TheNiceGuy’s comment above regarding a “formula for vine length and efficient fruit growth”.

I don’t know the exact formula, but if I remember correctly, it has to do with the number of leaves to fully ripen the clusters of grapes. It’s something like 12 leaves per cluster which works out to something like 3 or 4 feet of shoot length. Anything less than that and the grapes won’t fully ripen, and anything more than that is overkill and will throw the vines out of balance for the following year. (Balance has to do with keeping the vines in that sweet spot where they grow just enough to ripen the grapes, but not enough to store too much energy in the plant/roots which would cause excessive growth the following year leading more pruning and more time per vine.)

For the wine growers, knowing the optimal shoot height (or trellis height) is important because they can calculate their row spacing based on the height of the vines and the amount of light vs. shadows (from the adjacent row) that the vines receive. This allows them to pack in as many vines per acre as possible while still allowing the grapes to fully ripen while keeping the vines “balanced” and keeping vegetative growth in check. For home fruit growers, it’s not nearly as important, but the point is, beyond certain shoot length/number of leaves, it’s overkill

This was a very long winded way of saying that so long as there are enough leaves (exposed to the sun) to ripen each cluster, I don’t think it matters if you grow up, down or sideways.

Here’s an article on different trellis types. It’s for wine growers, but it applies to any type of grape:


Mr.Clint your set up looks great. Simple and effective. I have a question as I am a new grape grower. When the main trunk of your vine makes its way to were your lateral wire starts do you make a heading cut to force new growth to be selected for both laterals? Also at what height do the laterals need to start? It looks like yours start about three feet or so is that about right? Thank you for posting those videos they were very helpful for a grape novice.

Thanks for the kind words! Turns out that I don’t have any pictures of the vine fully pruned.

The lower wire is the typical two cordon setup, about knee high for me. I prune the cordons to the end of the posts and spur prune any of the shoots. That basically leaves about two joints per shoot. I then have a central leader that reaches to the top wire, about armpit level, and have trained two more cordons. Note that there is absolutely no advantage to these upper cordons other than offering Summer shade and privacy for the window behind it. There is also a 1/2 conduit stabilizer bar at eye level that gives me a way to route the shoots away from the wall. That’s the beauty of backyard orchard culture, I can prune everything to a size and configuration that is ideal for me. :thumbsup:

I’m experimenting now with some Summer thinning cuts --the idea is to provide better balance, light and air flow this year. The rains have brought on a lot of flowers that need to be thinned anyway.

An extra set of cordons for privacy. That is a great idea. I also use fruit for such things. I have used espaliered pears to hide an ugly stretch of fence. One more question if you dont mind. In your first year when the central leader of your vine reaches your first wire were you want your cordons to start do you need to make a heading cut to force the lateral growth or do just keep the cenral leader going up and let other buds develop for the laterals or is there another method? My vine just arrived recently and was just planted and cut back it is starting to bud and I just want to make sure I have a good game plan. Thanks again Mr. Clint. Sorry to pester you with so many questions.

No problem at all. I will IM you.

:disappointed: I was looking forward to reading the answer. Would you share it here?


Dear TheNiceGuy! I’m interested in table grape and especially to Seto giants grape. Please could you send me an e-mail to slezak.peter@centrum.sk I need some information about this grape, but I don’t know how to send you personal message. Thanks. Peter.