Why did my concord grapes not all ripen at the same time? We lost quite a few due to uneven ripening.
Some grape selections are more prone to uneven ripening than others, and concord is one of them. Many factors can influence this - extremely warm summers, extended periods of cooler temps, lack of fertilization, competition from weeds and other vegetation, improper pruning, bugs, weed killers - these are some of the factors that can play a role.