For years gardeners have enjoyed everbearing raspberry varieties, such as 'Heritage'. These varieties fruit twice a year -- in summer and fall. Now from the University of Arkansas comes a breeding breakthrough with another small fruit. 'Prime-Jim' and 'Prime-Jan' are the first everbearing blackberry varieties to become commercially available.
Unlike other blackberries, 'Prime-Jim' and 'Prime-Jan' fruit on the first-year canes (primocanes) in early fall and then again on the same canes (floricanes) the next summer. This allows for two blackberry crops a year. Since the canes of these new varieties are only hardy to USDA zone 7 (roots are hardy to zone 4), gardeners in colder areas should mow down the old canes in spring and allow the new canes that grow to produce a fall crop.
'Prime-Jim' is slightly more vigorous than 'Prime-Jan', but the latter produces sweeter berries. Both are thorny varieties that produce large fruits.
For more information, contact berry nurseries, such as the Indiana Plant Farm (http://www.inberry.com).