I planted three grape vines some years ago, supposedly seedless and maturing at different times: Himrod, Suffolk Red and Glenora Black. I was hoping for large grapes. By now the vines are fairly large: the diameter of the vines about 1' above the ground is roughly 2". The main trunks climb about 8' up a trellis and then go about 4' along the top of the trellis. They produced grapes last year and this year. In each case, they are tiny tiny grapes. At their largest, they do not exceed .5" diameter. Generally less than that. They are so small that no one in the family - and we all love grapes, so that store-bought grapes are consumed in a flash - thinks that it is worthwhile to even pick them off the stems so as to eat them. Unless this improves, I will treat it as a failed experiment and cut them down. But before I do that, does anyone know if I am doing something wrong? Or are these just tiny varieties? I prune the vines each year, but am not sure that I am doing it correctly (The terminology in all the pruning books describes parts of the vines using non-intuitive words and I have to guess what they are talking about). I do not use any artificial stuff in my yard. The vines are in full sun. The soil is very fertile - maybe too fertile? - for two vines, not so fertile for the third. They get lots of water. The vines are only about 5' apart, so maybe too close? I try to keep the new growth under control during the summer, but it grows like mad and right now sunlight does not penetrate past the upper leaves.
Hmmm... this newsletter (PDF) from North Carolina State Univ suggests one possibility (you'll need to scroll down in the document) - powdery mildew affecting the fruit in the early stages, then disappearing from sight, but still causing reduced size in mature fruit. Perhaps Ralph will pipe in, though - he's pretty busy at this time of year, I imagine, but he'll give far better advice than I'm able to.
Hi soccerdad: Firstly, these are not inherently small varieties; the Himrod and Glenora should reach 3/4" and the Suffolk slightly larger (a 3/4" grape is more than double the volume of a 1/2" grape). I suspect the vines are carrying more fruit than they can reasonably handle and accordingly are unable to reach the "normal" size. This is an in-season pruning issue and can happen even if you correctly dormant pruned them. The solution is to limit the number of bunches and tip prune the shoots so they each have about 20 leaves per bunch. It's late now, perhaps too late, but this is a slow year, so I'd be inclined to try it anyway: what's to lose? Remove half of the bunches, selecting the best looking ones to keep. Prune away the leaves to expose the remaining fruit to the sun. Next year do the bunch thinning when the grapes are about BB size (1/8" or 3mm). Count your bunches from this year and try for half that number, adjust up or down according to the bunch sizes. Watch these links: http://connect.ag.vt.edu/westover1/ http://connect.ag.vt.edu/westover2/ http://connect.ag.vt.edu/westover3/ for a free pruning lesson. This year has not been one of our best, but the actual numbers (at the end of July) are only about 5% below average. We've been spoiled by the last three years (3 years ago was almost 50% above the 10 year average) but even in an average year these three varieties should produce excellent eating grapes. It's the folk with the Pinot Noir and other vinifera that will be struggling to get over the finish line this year. Ralph
