Why Don't My Blackberries Ripen

Varieties

• Not all blackberry varieties produce sweet fruit. If berries on your plants never develop sweetness, you may own an older commercial variety, such as Brazos. Brazos, released in 1959, produces fruit that tastes slightly sour when fully ripe. Brazos processes well, and makes a good berry for pies, preserves and other sugar-laced products. The Boysenberry, a type of trailing blackberry, produces large soft fruit with excellent flavor but of a tart quality. Newer varieties of blackberries developed at the University of Arkansas have more sugar and more flavor. Navaho, an erect cane blackberry, yields fruit with long shelf life and sweetness.

Season

• Blackberry varieties fruit during different seasons and the length of the harvest also varies with type. Not all varieties produce crops in all growing areas. Some blackberries need winter chill of a certain minimum duration to bloom. Choctaw blackberry ripens early in the summer but needs 300 to 400 hours of winter chill to trigger blooming. The Kiowa cultivar needs only 200 hours of cold but blooms later in the summer than Choctaw. If berries on your plants don't ripen at the same time as other berries in your area, you may own a type that matures later in the summer.

Detecting Ripeness

• Blackberries develop full sweetness only if left on the canes until fully ripe. For most blackberries, red color indicates unripe fruit. Blackberries turn black before fully ripening, going through a shiny stage before developing full sweetness. If picked while shiny black the fruit often tastes sour. Left on the canes, the shiny black berries develop a dull sheen that indicates high sugar content. Firmness of berries at maturity varies with the cultivar. Some types produce berries that keep their shape well even when fully ripe, and others become soft and fragile. A fully ripe berry separates easily from its stem.

Tips

• Checking the patch for dark berries with a dull sheen every two days during the harvest season allows growers to harvest blackberries at full maturity for best flavor. Picking berries slightly before full ripeness gives fruit with better shipping quality. Fill containers only four layers deep to keep the berries in best condition, according to the Virginia Cooperative Extension. Fully ripe berries damage easily and injured berries spoil quickly. Refrigerate ripe blackberries within 30 minutes of picking. Blackberries store best at temperatures just above freezing. After berries chill, wrap the containers in plastic to prevent dehydration and shriveling.