Grand Forks County Extension
Horticulture
Steve Sagaser, Extension Agent/Horticulture
151 S. 4th St. S302, Grand Forks, ND 58201
(701) 780-8229 Fax (701) 780-8309
stevan.sagaser@ndsu.edu
NDSU Extension Service Horticulture
Frost threatens late-ripening apple crop (October 8, 2009)
Killing frosts are expected this weekend, but much of the apple crop is still on the tree. Cool weather this summer has delayed the ripening of this year’s crop.
Apples freeze at approximately 26 degrees, but in many cases will not suffer damage until they are frozen several times or for extended periods of time. A light frost is actually desired, since it accelerates the ripening of the fruit.
Commercial growers start to worry when temperatures dip into the low twenties. In this case, it is advised to harvest as much of the crop as possible.
The best way to tell if an apple is ripe is to look at the background color of the fruit, found at the top of the fruit near the stem. For red apples, this background color will turn from green to yellowish green. Harvest when the yellowing appears. Other symptoms a ripe fruit is that its seeds are dark brown and the fruit can be easily removed from the twig.
Harvesting should not be done during freezing temperatures since apples are more subject to handling damage at that time. In this instance, it’s best to let the apples stay on the tree until the frost has left the fruits.
Harvested fruits are especially sensitive to frost damage when stored—even more sensitive than apples left hanging on the tree. Store your harvested crop under protective cover; heated if needed.
Frozen apples will have a hard, glossy, and wrinkled skin, often with a purplish discoloration. Severely frozen fruit will turn brown and mushy. Frozen apples should be used promptly since they will not store well.
