Answer: If your blackberry is an upright type (as opposed to trailing) it needs isolation from other plantings because it sends out suckers many feet from the parent plant. You should be safe setting the raspberries 20 feet away. If the blackberry is not an upright type, you can get away with planting the raspberries a bit closer. In any case, locate the raspberries where you can control the volunteer plants that will spring up.
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