Canes or spurs?

Canes are just long “branches” of one year old wood with one or two dozen buds along their length. If they had just a few buds, four or so, then they would be a lot shorter and we would call them spurs. I had been spur pruning because it’s easier to take vines in and out of pots, while I trim their roots, without long fragile canes whipping about.

Letting the vine decide

Easier doesn’t get you very far if the varietal doesn’t bear fruit that way, so last year I pruned to canes. I was careful not to jostle them when I tended the vine, re-potted it, or just walked past it. Well it looks like it may have been worth the effort. I’ve noticed a few clusters on my Swenson Red and I’m looking forward to my first crop in three years!

Scaling up a greenhouse

Jeff Chorniak inspired me to grow grapes in my suburban backyard and he used a collapsible greenhouse to extend the growing season. By sheltering his Cabernet Franc in this way, he made early spring and late fall just a tad warmer, and that can make all the difference when you’re growing grapes in Toronto. I’ve never done that myself, but the possibility of a cooler than normal season has me thinking about it. I’ve also wondered if the concept could be applied to a vineyard, by using plastic sheeting the way gardeners use row covers.

Some Puget Sound growers are doing just that. I’m hearing that overnight low temperatures, inside a tented vineyard row, are as much as 10F (5.5C) warmer than neighboring untented rows. On a clear day, under bright sun, it can get up to 15F (8.3C) warmer. “As much as” and “up to” are always tip offs that typical performance will be less, and that’s probably true here. Still, every degree helps and this might be a good way to cope with a cooler than normal year.

Left to themselves, grapevines will push out more clusters of fruit than they can ripen well. Making wine from such grapes will be disappointing: not enough sugar, poor flavor, too much acid. The problem is that a given vine can only pull in a finite amount of nutrients through its roots, and only produce a finite amount of sugar in its leaves. Divide that finite amount by an increasing number of grape clusters, and each one will have less and less. At some point, “more” becomes “too much” and you’ll get a large crop of poor grapes that will never produce anything but poor wine.

Yes, and that’s the problem

Grape vines will do this because they’re not trying to make wine. All they want to do is produce something that animals find more appealing than a nearby twig or blade of grass, and they want to produce as much of it as possible. Ok, they’re not self aware, and therefore aren’t really trying to do anything, but we are. We’re trying to make wine, and the tendency of the vines to produce as many grapes as possible gets in the way of that. So, part of the reason we prune them is to reduce the yield down to something that will ripen well. Sometimes, even after pruning, the vine will push too many clusters, and that’s when we need to thin. Another approach would be to prune less aggressively than normal, then thin to keep the vine from overbearing.

A specific deadline

You can’t just lop off nearly ripe clusters of fruit in the fall and call that “cluster thinning.” To get the most benefit from this technique, you need to thin the clusters before the flowers open. Its probably true that there will be something to gain from a “better late than never” approach, but it won’t be much. Timing is critical here, so monitor your vines closely after bud break and make sure you thin before the flowers open.

And a fuzzy target

If you don’t like deadlines like that, then you’ll be happy to know that the idea of how much to thin is a lot more vague. I’m going to have to punt here and say that “it depends.” It depends on the varietal, your location, the year to year climate variability, and your own goals. You may be able to find advice, from other growers in your area or from books, about how many high quality clusters this or that varietal can produce in your area. In the end, though, nothing can substitute for experience with living vines in your vineyard. Get to know your vines by trying fewer clusters this year to see if that improves the quality, or advances ripening. Maybe try a few more clusters to see if that boosts yield without harming the wine. Knowledge like that is priceless and will help you make better wine from your own grapes.

Further reading

Cluster thinning is aimed at efficient use of sugar in the vine. My last article on canopy management was about leaf pulling, to promote efficient sugar production in the vine. These two goals are opposite sides of the same coin, so if you missed the first article, you might want to click here and check it out. To make sure you don’t miss future articles, subscribe to this blog. Its simple, its free, and you’ll see every article without having to check back manually.

I’m still learning about canopy management. I’ve gotten a lot out of Jeff Cox’s From Vines to Wines. It’s where I first read about cluster thinning, and I still refer back to it. What makes it a great book for the home winemaker who wants to grow his own grapes is that it covers both topics really well. The first part of the book covers the viticulture, from which vines to plant, site selection, pruning and training, and pest management right through harvest. The second part picks up right where the first part left off and talks your through making wine from the grapes you just harvested. From primary to finishing and ageing with troubleshooting information and a section on tasting.

Leaves in the shade: Like open windows with the AC on

The idea behind leaf pulling is that a leaf in the shade isn’t just idle, it’s holding back the vine by consuming sugar and nutrients that could be going to productive leaves or fruit. So if you pluck leaves that are in the shade, or those that shade other leaves, the vine will still get almost as much benefit from photosynthesis as before, but will not have the drain of non-productive leaves. Done correctly, this will mean better fruit. It might even mean earlier fruit.

Fruit in the shade: A more complicated trade off

Sunlight affects ripening fruit in different ways. Too much can burn, and not enough can delay ripening. Here, leaf pulling decisions are more tricky. What do you do about a leaf shading a grape cluster? If you pull it, the cluster will get more sun, but at the cost of reducing photosynthesis and sugar production. I don’t know that there’s a this-always-works-answer here. In cool seasons, the risk of burning may be less so you might be more inclined to pull leaves that shade fruit clusters. This might also be true later in the season, after the hotter July and August days are behind you. On the other hand, it’s those cooler seasons, or times of year, when you want to turn every photon of light into sugar. For what it’s worth, I’m planning to pull leaves for maximum photosynthesis through the hot summer, then open up the clusters to sunlight in late summer/early fall.

The flip side of maximizing photosynthesis is making the best use of the resulting sugar. I’ll talk about doing that with cluster thinning in my next canopy management article.

Pinot Noir: 21 oz (600 g)
Leon Millot: 37 oz (1050 g)
Price 17 oz (480 g)
Siegerrebe: 11.5 oz (325 g)

All: 86.5 oz (2455 g)

5 lb 6 oz isn’t a lot, but it’s more than last year’s 4 lb. I had more favorable weather last year, this year we had a cold and rainy fall and a cooler summer, and this year I lost part of the crop to critters. So, all in all, not a bad year.

It gets better. Norton is tolerant of many fungal diseases, including the common ones in my neck of the woods, and phylloxera. Sounds like a grape I’d like to grow! Well there are at least two drawbacks. First, it’s difficult to propagate from hardwood cuttings. Ok, that would be a nuisance, but it is being grown and propagated, so I don’t think that’s a deal breaker. The deal breaker is that it requires a long growing season. There’s a lot to like about the Puget Sound, but we are limited in the wine grapes that will ripen here.

9/21/07 : 3 oz (100 g)
9/26/07 : 2 lb 2 oz (975 g)

2007 Total: 2 lb 5 oz (1075 g)

That compares with 2 lb (just over 900 g) in 2006.

I started taking some Pinot Noir as well, but changed my mind after three clusters. They’re just not ripe yet, so I’ll leave the rest to face the rain. Those three clusters weighed in at 7 oz (210 g), and will be joining the Leon (and Price and Siegerrebe) in the freezer until I complete the harvest.

The incursion into my bonsai vineyard on Wednesday knocked some grapes to the ground. I gathered these up, ate some, discarded some, and froze the rest. This was the official, if unintentional, start to my grape harvest and it totaled 3 oz (100 g) of Leon Millot. At that point, I decided to bring in the Siegerrebe and the Price. They’re both early ripeners and they seemed ripe when I tasted them. I hand destemmed, lightly washed and froze the grapes. So in addition to my Leon, I’ve got:

11.5 oz (375 g) of Siegerrebe from 1 vine
17 oz (500 g) of Price from 2 vines (I have three, but one didn’t bear this year)

After harvesting three of the eight vines that will bear this year, I have 9.5 oz (290 g) per vine. If that’s the yield I get for the Leon Millot and the Pinot Noir, then I’ll get 4.75 lb (2.3 kg) total this year. Um, that’s a bit less than the 20 lb (9 kg) I wanted!

Marsha was frantic and ran to wake me up this morning. I was still groggy, so it took me a while to figure out that all the grape vines had been knocked down. We didn’t see what happened. Nobody and nothing was about. I think it was an animal, probably a raccoon though. I have bird netting over the vines, and that did two things – one good and one bad. The good thing was protecting most of the grapes. Whatever it was only got two small clusters. The bad thing was binding all the vines to each other, so that when one was knocked down, they all went down.

As you can see in the above photo of a Pinot Noir cluster behind it’s protective bird netting, order was restored. I remember how surprised I was at just how many different kinds of bird netting there is but, as with most things, you can keep the birds out on a budget or opt for a higher end product. I opted for the affordable option.

Planning for the future: Bird netting on a frame and a temporary greenhouse?

One improvement I could make would be to string the netting on some sort of external frame, rather than draping it over the vines an I do now. As birds, raccoons, and other small animals try to get at my grapes, they would jostle the frame instead of the vines. That would make the vines much less likely to tip over. I’ve thought about building such a frame before; I could also hang plastic sheeting on it, turning it into an impromptu greenhouse, in early spring and late fall. That would extend the growing season a bit, and might allow me to experiment with grapes need a warmer climate.

Harvest time is almost here, in fact I may make a point of speeding up the harvest for the earlier varietals, and after that I’ll have all winter to think and plan.