Answer: The 'Illini' hardy blackberry was developed by the University of Illinois for colder winters. Tests showed that it produced 8 years in a row with temperatures to -23. Zone 4 has average annual minimum temps of -30 to -20. It's available through Miller Nurseries, 5060 West Lake Road, Canandaigua, NY 14424, 800-836-9630, http://www.millernurseries.com. You might check with them to see if they have any customer experiences in cold weather.
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