This variety of seedless grape is usually ready for consumption by mid-July. These stafidia (Σταφιδια = raisins) are meant to be used either as table grapes or dried. Every year the grape variety pictured have a difficult time as the vines are meant primarily to shade an outside dining area and shade + grapes usually means problems. The fruit needs sunlight to develop sugars and to maintain healthy, fungus free growth.
As this is an unusual situation where edible fruit and shade are desired, the grower needs to thin the canopy regularly to be sure that some sunlight comes through and that there is space for air to circulate up, through, and around the leaves and fruit. The grapes also need regular precautionary dusting with copper sulfate and maybe some BTK (Bacillus thuringiensis kurstaki).
The same rigorous regimen is applied in commercial grape (Σταφίλια – Stafilia) production (wine/table grapes) where vines need constant attention to be sure the plants get the required sunshine, air circulation, watering, and dusting.
For the grapes (raisins) pictured, this attention doesn’t stop after the mid-July harvest. A well maintained vine of this variety may produce a second crop in the early autumn around the time when wine grapes are harvested.