An update earlier this month from Iowa State University (ISU) Extension stated that, “Home gardeners can successfully grow grapes in Iowa’s climate. Grapes can flourish in a backyard garden or a vineyard, but obstacles like insects and knowing the proper harvest time can keep them from reaching their full potential.”
The ISU news item, which was presented in a “Q and A format,” noted that, “Color alone, however, should not be the sole basis for harvesting grapes. Berries of many cultivars change color long before they are fully ripe. At maturity, individual berries are full size and slightly less firm to the touch. As a final test, taste a few grapes for sweetness when berry size and color indicate the fruit is approaching maturity. Harvest grape clusters when the berries are sweet.
“When harvesting grapes, remove clusters with a knife or hand shears.”
The update pointed out that, “Several factors could be responsible for the uneven ripening of the berries within a cluster. Possible causes include overcropping (too many grape clusters on the vine), a potassium deficiency, moisture stress and 2,4-D damage.
“Overcropping is the most common cause for home gardeners. An average grapevine may have 200 to 300 buds which are capable of producing fruit. If grapevines are not pruned properly in late winter, the number of fruit clusters may be excessive.”
Also, the ISU update on grapes added that, “The best way to prevent birds from eating the grape crop is to place netting over the grapevines. Netting can be purchased at garden centers or through mail-order companies. When placing netting over the grapevines, make sure the netting is secured to the ground to prevent birds from entering from below.”
