How Can I Tell If My Berry Bush Has Blackberries on it?

Normal Fruiting

• Healthy blackberry plants growing in well-drained fertile soil with good air circulation and full sunlight stand the best chance of producing a normal crop. Bramble fruits self-pollinate, setting larger berries if worked by pollinating insects like honeybees, but setting smaller fruit if untouched. Berries form from groups of drupes. Each drupe begins when one of the flower's ovaries fertilizes and produces an embryonic seed. As petals wither and fall, green drupes appear in the center of the blossom. Well-formed berries consist of a solid wall of drupes around a central core.

Crumbly Berry

• Plants suffering from "crumbly berry" problems produce berries with few drupes. Some flowers might form only one or two drupes, and others produce small drupe clusters without enough drupes to hold the berry shape. Drupes ripen normally, but berries crumble apart when picked. Lack of pollination could contribute to crumbly berries, and other problems also prevent drupes from growing. Unusually wet weather could foster fungal infections such as "blackberry rosette." Insects could damage the developing berries and cause individual drupes to fail. Fungal diseases such as orange rust could weaken plants so much that canes produce little or no fruit.

Harvest Cycles

• Fungal diseases often run in cycles, with good years of fruit production as well as bad years, depending on weather. Late frosts could kill blossoms before fruits form, and in some years populations of damaging insects could reach unusual numbers. Because growing conditions vary even in a small bramble planting, some plants could produce well while others produce almost nothing in the same year. A pattern of steady decline, beginning with only a few plants in the patch but including more year by year, indicates viral disease. Viral infections could sterilize every bramble in the garden if not controlled.

Controlling Viruses

• Tobacco ringspot virus and necrotic ringspot virus cause similar problems in blackberries. Infected plants grow poorly and new leaves develop distortions. Fruit shows the crumbly berry pattern. Leaves develop streaks or rings of yellow tissue. Disease spreads through sap-sucking insects called thrips. If plants show the signs of viral infection, dig them up and burn all parts, including roots, well away from the berry patch. Avoid planting new brambles in that location for several years. Wild brambles could carry viruses that jump to domestic cultivars. Allowing wild brambles to grow within 500 feet of domestic varieties puts the patch in danger of infection.