Last summer was a warm one, with numerous days topping 80F (27C). It was also on the dry side. The farm received 2.88 inches of rain (73 mm) during the three month period May through July. In the past, we assumed grapevines didn't grow much during the summer here because it was too cold - both the air and ground temps. Well, this year when we saw a string of very warm days and warm nights, we were puzzled to see the grapevines not growing more than they had in past summers (rainy or not). So, we contacted a very knowledgeable grape grower in Wisconsin. He asked how wet the ground was. WHAT? I thought grapevines didn't need water in places where it rains in the summer. Wrong!!! Research revealed that each vine requires 6-10 gallons of water each week, or an inch of rain. Well, we never get that much rain before August - and then the vines are starting to shut down. So, we started pouring water on a few vines to see what would happen. Our Arthur Pinchbeck (Canadian variety) vine literally took off! In 5 weeks it grew 5 ft - compared to 1.5 ft (0.5 m) last summer. Who says grapevines won't grow in Interior Alaska? At the end of the season, it was taller than me. It still remains to be seen how much of the vine hardened off sufficiently for the winter, but we're hoping for at least 3 ft. (1 m).
We added a number of new cultivars to our trials this past summer, including ES M-1-27 (a very early variety bred by the late Elmer Swenson). Vandal Cliche, and Marquette. We also were able to add Baltica back into our collection after losing it two years ago before we could get it planted in the vineyard.
We also reorganized the existing vineyard (now at about 135 plants on 1/8 acre or 0.05 ha). When we did this a few new lessons were learned. Every vine that we dug up, with the exception of Sipaska and Louise Swenson, had really no new root development since being planted between 1 and 3 years ago. None, nada, zilch. That was disappointing. And, in cases where the crown of the vine was planted 12 inches (30 cm) deep (most were planted only 3-5 inches (<15 cm) deep), all older roots above about 8 inches (20 cm) were dead. There were a few white new ones in that zone, but no older roots. Why? Good question. Perhaps a lack of water. Perhaps winter cold (though we have documented that the ground doesn't drop much below freezing in this zone, which should not be a problem for our hardier vines). In the case of Sipaska and Louise Swenson, they both had older roots extending 12 inches (30 cm) or more down into the ground. Nice, healthy looking roots at that. And Louise Swenson is supposed to be particularly prone to drought stress! Now that the vineyard is reorganized with all vines planted at least 8 inches (20 cm) deep, we hope for better growth in the future. The obvious lack of a root mass on each vine also contributed to the poor summer growth on vines.
One thing that reorganization did not solve, was the way we were planning on trellising the vines. Reading the literature, it is suggested that vines be planted in rows that run north-south and up and down the hillside (where appropriate). Well, since our land slopes downhill to the south, we were planning on trellising them up/down the slope. That would improve the stability of the trellis, too, since all stress would be pulling parallel to the row alignment and we could counterbalance that with a ground auger on the uphill side of the trellis. However, we realized that orienting the trellis this way meant that the fruiting zones in each row (based on a low-cordon training system with vertical shoot positioning or VSP) would be shaded until almost 11 am and again after about 5 pm each day. Remember that at 65 degrees north latitude, the sun doesn't rise all that far above the horizon for much of the summer. Our original layout was based on rows running east-west (across the slope rather than down it). Putting a trellis up for that system would mean that the freeze-thaw cycles in the ground would allow the trellises to slowly lean over downhill (that is what the pilings are doing under the cabin at the moment). An east-west alignment would greatly reduce shading, but would not allow full sun exposure of the north-facing side of the clusters. Turns out that this problem would not be solved using north-south rows, unless we spaced the rows out significantly more than our current 6 ft (2 m) row spacing. The jury is still out on the best orientation. We will probably run a trial using both orientations for the same variety (probably Alpenglow, since that is a readily available variety that hardens off significant wood for the winter) and see what happens.
Another discovery this past summer was the importance of leaf pulling in the far north for more than fruit exposure. Typically, "northern" vineyards (but still well south of our vineyard) practice pulling leaves in the fruiting zone once veraison has begun to get more sunlight on the fruit and encourage the ripening process (adds heat and direct sunlight on the berries). Well, as our serendipitous experiments usually turn out, we learned a valuable lesson in "leaf pulling" due to the very dry summer and abundant sunshine. The bottom 3 ft (1 m) of our Arthur Pinchbeck vine had all leaves facing north. Odd, I know, but that is how it grew. Above that, the leaves oriented in all directions. Our theory (based on fairly sound science) was that the leaves were trying to avoid the sunlight to reduce water loss and oriented themselves as far "out of the sun" as possible. This is a common strategy used by plants that are water stressed. By turning the top of the leaf (most photosynthetically active surface) away from direct sunlight, photosynthesis is reduced. In addition the leaf temperature is reduced, stomatal opening is reduced, and water loss decreases. Uh, that's all well and good, but why was that important this year. Turns out that here, the hardening off of grapevine shoots in the fall (and subsequent survival and budding out in the spring) is very dependent on sunlight exposure during the latter half of the summer. From our observations, shoots need more than 4 weeks of direct sunlight on them in order to adequately mature the shoot and begin forming periderm. We saw periderm formation on Arthur Pinchbeck and Alpenglow by mid-July this year - compared to mid- to late- August in other years. Once we started pulling leaves on other varieties, we saw significantly more periderm formation on them than in past years. The most noticeable variety was ES 80. This Elmer Swenson variety (one of his first) has turned yellow and dropped its leaves in the fall every year in the past. However, it has never formed periderm. This year, with its basal leaves pulled beginning in late July, it developed periderm over most of its shoot and looked really good going into the winter. It has fairly large leaves that tend to shade the shoot. Remove the leaves later in the season and viola! it forms periderm. Leaf pulling did not affect all vines equally and our largely V. labrusca derived vines were the least affected. Those with more V. riparian or V. amurensis responded more strongly.
Speaking of V. amurensis, we also ran an experiment with grow tubes this summer and found that this species requires substantially more water than our other species/varieties. Even in the middle of the heat and dryness, there was moisture condensing inside the grow tube on Amur-1 (one of two remaining seedlings from several years ago). This species comes from northeasern China/Russia where the summers are hot and very humid and winters are cold and very dry. So, summer droughts are not its specialty - winter droughts, on the other hand, it handles with ease. We will have to really water that one well next summer to see if it will grow better. As usual, this vine was completely dormant 123 days after budswell (May 13-September 13). Now if it will produce fruit and ripen it in that time, we're onto something.
Understand that when we say "serendipitous experiment", these experiments arose entirely on their own. We just observed the results. A well documented serendipitous experiment here on the farm was the discovery that covering trailing blackberries with row cover over the winter improved winter survival. We were too busy one winter to remove the row cover we were using to help ripen blackberries in the fall and the next spring we found live canes under the row cover and dead canes beyond the cover. We now (almost always) cover our most productive blackberry plants with row cover for the winter. More on that ongoing experiment in a future post.