I've been lucky enough to be able to visit my parents when they are harvesting their table grapes - not so easy most of the time when they are in Upstate New York and I live in New Zealand!!
So I thought some info on growing and selling table grapes might be in order!
In the world of wine grapes, berry composition is king. The goal is to get those berries to the proper chemical and sensory levels, as well as being free of disease.
For table grapes the goals are all these, but also there is an appearance issue. So my parents need to be very careful about spraying anything that might leave a visible residue on the grapes. In some cases, this might preclude using certain types of sprays!
As well, the presence of an undisturbed bloom on the grape (this is a waxy coating on the berry which, when untouched, makes the berries look a bit white. If it's rubbed the berry goes shiny) is also desirable. This means the less the fruit is handled, the better!
Then you get into the shape of the bunch, which needs to be something like a nice stereotypical grape cluster, not some really small, scrawny or lopsided thing. As well, the clusters can't be too tight (that makes it difficult to pick the berries off when you want to eat one) or too loose (as then it doesn't look filled out enough and too leggy). Packing tight clusters is also a problem, as they aren't flexible enough to fit into conventional 20lb boxes (i.e. if you fill a box with tight clusters, the weight will be less than 20lbs).
So picking table grapes is a much more labour intensive process than wine grapes. Sure, with ultra-premium wine grapes, you will be doing some sorting in the field, such as removing diseased clusters and not picking second set and the like, but with table grapes, every imperfect berry should be removed from the cluster.
This means grapes that are too small, blemished in some way (sunburn, bit of sooty mold etc.), bird pecked, diseased or anything else must be snipped off. In some cases, this can result in a large, nicely shaped cluster when it comes off the vine being trimmed down to a scruffy looking scrag of a cluster, not suitable for the market.
In any case, there is a lot more attention paid during the harvesting process, and even during the growing season special considerations have to be made.
The returns can be pretty high, but if you don't have the labour to do all the work, it's all pretty academic, isn't it? :-)
The fruit my parents' grow is all seedless, varieties bred in Upstate New York, at the Geneva Experiment Station, and also a few other places, like Arkansas, which has released a number of varieties. The main difference these grapes have over those typically found in the grocery store is that they are bursting with flavour!!
So which would I rather be? A winegrape grower, or a table grape grower? Hmm, Table grapes are nice, but not as nice as wine!! :-)