John Marshall From the Vineyard
Editor’s note: This is the first of a series of columns by John Marshall of Great River Vineyard in Lake City, Minnesota
This season, like every season it seems, has been very atypical. Spring started us off cool, which brought on a late blossom. It gave us more time to get our spring work done but got the growing season off to a late start. This, mixed with copious rain (we got 7″+ in one week at one point) we feared would interfere with pollination and moreover set us up for intense fungus disease pressure. It was a spring of uncertainty.
Those who got their early preventive sprays on were generally OK for when it turned warm it did so with a vengeance. Growth, that had been so uncertain to begin with, took off and made our vineyards and everything else, look normal. To add to the uncertainty, when it finally quit raining, it stopped entirely. We here at GRV like many of us, did not have a significant rain during all of August. This, together with the mid-season heat, aided ripening and brought our sugars up and our acids down which gave us hope that this late year might not be a disaster after all.
As a kind of coup de grace we got a widespread killing frost in mid-September. Although we always seem to say this, it was truly a bizarre season. The fact that the grapes are coming in now in reasonably good condition with acceptable sugar/acid balances and acceptable pH levels speaks a lot about the flexibility of grapes and Vitis in general. It also says something about the flexibility of our growers and the winemakers who must make palatable wines from the odd assortment of grapes that come in from year to year. This is not California! We have to live with a lot of variability.
The year not only underscores the flexibility of grapes but emphasizes the importance of getting the early sprays on and keeping watch. In fact, I had my head deep into getting our nursery started this spring and thus was trying to ignore the vulnerability of my Valiant crop that is highly susceptible to Downy Mildew and Black Rot.
The copious rain was putting them at risk and, sure enough, while I was down directing crews and putting in cuttings, Downy Mildew began to affect the flower blossoms on my Valiant. By the time I got away and got a spray on, Downy Mildew was started and every time it rained, which was often, it took off again. While my other varieties were mostly clean, the Valiant crop was a disaster. In Western North Dakota where it is chronically dry, growers raise Valiant with little problem. One grower there actually told me he ‘does not own a sprayer”. Not the case in rainy, humid Minnesota and much of the region. I own a sprayer and I use it. So does virtually every grower I know.
Even so, despite the remarkable weather and the challenges that beset us all the fruit has come in and the crop is not so bad. Hopefully you arranged for buyers long ago. I have begun thinking about who will want my fruit next season, even now, as I sell this one. Will this guy need my grapes next year or is his planting coming in now and I will have to find another outlet? What will I be likely to have next year? Who will want it? What terms can we work out? Hopefully this can all be agreed upon by mid-winter or so. If you plan to have a crop next year you will want to contact possible buyers this winter and see what can be worked out now not during August and September.
In addition, winter is coming. I always find it kind of lonely when I walk down my vineyard rows in fall and all the vines are empty of grapes. The canes and any leaves that remain hang in a listless, silent, suspended animation, sort of drifting off to sleep now in anticipation of the true cold that is coming. Nevertheless, it is not time for the grower to lose interest in what is going on. Preparation for the coming growing season can begin now.
Did you have any serious disease problems? I did in my Valiants. I will surely plan to apply a lime/sulfur dormant spray as soon as the leaves drop from cold and the vines go entirely dormant, sometime later in October or early November. If I have time, I will apply it to the entire vineyard. Lime/sulfur is a powerful anti-oxidant that will essentially dissolve any fungus spores unfortunate enough to meet any of the droplets you apply this fall. It is a good way to at least partially neutralize fungal disease problems from the past and get a leg up on your preventive spray program for next spring.
In addition, if you had any Potassium deficiencies last season, fall is the time to apply potash. It is a Potassium-rich granite that can be purchased bagged or in bulk, usually in a very coarse granular consistency. It is available from any farmer elevator. It needs to be applied now and not next spring as this rock takes months to break down and percolate down into the root zone. If applied next growing season it will likely be unavailable until very late or after the growing season. It is most effective when injected into the soil although banding it onto the soil surface works also. Classic Potassium deficiency symptoms are light green growth, yellow or burned margins on leaves, isolated berries that are full size but remain green in ripe clusters and especially low sugar readings at harvest. If you suspect low Potassium take a leaf sample now (if the frost hasn’t burned your leaves already) and send it to a good University or private laboratory for analysis. A soil sample would not be accurate in this particular instance.
In addition, Roundup (Glyphosate) is most effective when applied this time of year. The product is taken down with everything else the plants are absorbing and storing away and is known to be extremely effective now. You can apply very late as long as there is still green on the offending or ‘target” weeds you are attempting to control. This will ensure a timely, effective and safe application and relieve you of this duty next spring when there is much more to do.
Loosen your trellis wires if you like, grub out any old vines that may have died, repair some trellis breakdowns that you see, maybe fill in some washouts from last springs abundant rains and generally get the things done you couldn’t get to during the growing season.
This story was reprinted by permission of the Minnesota Grape Growers Association (MGGA) and first appeared in the Fall issue of MGGA’s “Notes from the North.” Midwest Wine Press is proud to be a member of the MGGA. Please visit their website at mngrapegrowers.com