I applied a teaspoon or so of borax to my two red flame grapes last winter and it did improve the amount of fruit set (thank you HOS), but I still didn't get any complete bunches of grapes, most were maybe 50-90% set.
Should I add more borax this winter or look for other problems, like the big oak that's nearby (maybe more fertilizer to off set the oak's depletion).
No more borax. Applying it more than every 3rd year can cause toxicity symptoms.
Instead, leave fewer fruit buds at pruning time ( prune the vine more) or remove some of the flower clusters before they bloom to increase set in the remaining ones. Remove 25 to 30% of the total number. This is discussed in detail in The Grape Grower. http://www.bunchgrapes.com/pub.....tions.html
and get visual help from the DVD at http://www.bunchgrapes.com/dvd.html
I hybridized the Flame Seedless with an American hybrid and named it Richard Walden. The grape tastes much the same as Flame, but is far more resistant to botrytis and mildew. If it has one fault, it is overcropping, so you need to cluster thin, but otherwise it is a real improvement over Flame 
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