Walnuts Shriveled and Inedible

 

The most common cause of shriveled nut meats inside a normal looking shell is inadequate or inconsistent watering. If the tree suffers even one dry period during the time when the nut meats are developing and maturing, the nut meats may shrivel. The most critical period is July through October. Water stress may be exacerbated if the tree is on very sandy soil or if the soil is very shallow or compacted. Sandy soils tend to dry out quickly, and shallow or compact soils prevent deep root penetration, so the tree cannot mine water from deeper soil layers. When the tree runs short of water, one of the places it goes to get water is from the developing nuts, consequently the meats shrivel and fail to develop. Another cause of shriveled nut meats is insect injury. High aphid populations can produce large quantities of honeydew. If the honeydew coating the developing nuts is colonized by sooty mold (black fungus), the temperature of the nut may increase, causing the developing nut meat to shrivel. Finally, sunburning can cause shriveled nut meats. If the developing nut is exposed to direct sunlight, the husk may heat to the point where tissue injury occurs. The nut meat inside this injured husk may also be injured and shrivel as a result. To prevent the above problems, make sure the tree gets adequate and consistent watering. Also, keep the tree adequately fertilized, so it can produce enough foliage to keep most of the nut shaded while they are developing. It is also suggested that the ground under the tree be mulched or grass-covered. This helps moderate temperatures in the tree and also helps with water management.