Sour grapesreally.

I have a very hardy Concord grape in my backyard that has at least fair production. The grapes never seem to be as sweet as the ones I can buy at the fruit stands. I live in a zone 4b(if we're lucky) and the fruit stands are down in the valley at a zone 5-6.

I tried fertilizing the vine one year and all I got was a bigger vine. Maybe it was too high on the Nitrogen, but is there something I can do to the soil to make the grapes sweeter?

Sweetness of a specific cultivar is usually related to the amount of sun light received. You may not be getting as much sunlight and warmth as those down in the valley. I f you have not pruned your vine that may help.

I have pruned the vine, but I am certainly not an expert at it. I read about it, but it sounded like greek to me.

The vine is planted on the back fence and gets sun from about 12 hours of sun a day.

My grapes were on the sour side when they were in their first couple years of producing. Every year they seem to get a little sweeter. I never fertilize and prune every spring. My pruning is definately not professional. I just start cutting.

This vine is about 30 years old. A few years ago the grapes were quite sweet. Now they are not. Maybe it's just getting tired. I think I will take a sample of the soil and take it to our local Extension Agent.

Wow! 30 years old. Did you plant it? I would be interested in what you find out.

Yes, I planted it. I am twice as old as it is!!!!!!!!!!!!!! Scary.

I am going to dig around it and fertilize. I'll let you know. But I won't know until late September.

Be careful about fertilizing a concord grape. They are very prolific in their foliage growth. Usually fertilizer just makes more vines and leaves. I am in a much warmer climate but have good luck with grapes. I prume very heavily--leave 1 stem with 2 or 3 buds only every 6 inches or so down the cordon or main vine on the wire. Then when the grapes are about the size of peas I start clipping leaves off from around the bunches(not as time consuming as it sounds) so they receive more sun and airflow which prevents rotting. Also the longer grapes stay on the vine the sweeter they become. Perhaps you are picking too soon. In your area I wouldn't pick until just before frost. Be careful with the fertilizer, it causes the plants to put more growth in foliage and less into the grapes
RED

The year that I did fertilize I got just what you said--more vine, so I haven't fertilized. I will try trimming the vines from around the clumps of grapes. This year they are loaded. One interesting thing I noticed about the year that they were very sweet is puzzling--I was lazy and didn't water them at all! I have heard that watering tomatoes can actually water down the taste. Is that possible with grapes? Last year they were sour, I watered them frequently and picked them AFTER the first frost. Hmmmm!

You definitely want to water as little as possible, that could have done it. I am in a different climate, but I never ever water my grapes. Red gives some good pruning advice -- just count the buds you are leaving. I do 6 buds per foot. A simpler but less accurate method is just prune off all the new growth of that season down to 4-6" stubs.

Scott

Scott, In Baltimore do you get a lot of rain? Utah is a desert state and we can go a whole summer without rain on a bad year.

I remember another reason I didn't water at all that one year. We had a rattlesnake scare!!! A 46-inch rattler had been found in my next-door neighbors groundcover and in another neighbor's backyard garden. I wasn't going to trudge out through the weeds in my backyard to water anything!

Imred - Nothing ROTS in this dry climate, but it does dry out. We always let it freeze at least once before picking grapes or apples.

Linda, we get a great deal of rain here, so much that it gives the grapes too many diseases. But we can have long droughts sometimes as well. August is usually a light rain month. The soil is often like dust by the end of August.

Scott

Linda there is a disease called dry rot which will turn your grapes into raisin looking little crispy critters. That is what I am referring to. Adequate air circulation and a spray schedule is the answer for that. I lost all my concords 4 yr ago to it. That is the rot I was referring to.
RED