Answer: Since you have a fruiting pair (Blue Prince and Blue Stallion are usually recommended for Blue Princess), you might need to review some of the cultural conditions. The plants will be healthiest and perform best when grown in an evenly moist yet well drained, rich, acidic soil. One possible reason for light fruit set could be severe rain or other interference during the blooming/pollen season. A more common reason for lack of berries is pruning. Pruning between bloom time and berry formation removes the fruiting wood for the current year as well as wood that will set flower buds for the subsequent year. Flower buds are usually formed by mid summer, so a late summer pruning could actually stop berry formation for two falls. I hope this helps you trouble shoot.
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