Q. I planted blueberry plants in the spring, they have been doing well, up until recently. The berries that were on the plants when I purchased them ripened, there’s new growth and some of them are flowering again. Recently, however, the leaves have begun to curl under and are starting to turn slightly yellow. The plants are planted in full sun on the south side of house in a bed against the house, soil drains well and when I planted I added miracle grow and composted steer manure. As the weather grew hotter in addition to the morning sprinkler system, which runs 15 minutes every morning, I would give them hand watering in the early evening. I also added some coco husk mulch. The ground isn’t dry, but not really wet either. Can you please advice what might be going wrong with the blueberry plants as I don’t want to loose them. Thanks, Mark Williams – Bellevue, WA
A. Since the symptoms you have described seem to be isolated to the leaves I suspect that you are seeing an iron deficiency in your blueberry plants. Iron is important in many important plant cell processes including being parts of various enzymes (acting as catalysts) and in the formation of chlorophyll. The symptoms of iron deficiency show up on new leaves since because it can’t be moved from older leaves to support new growth. Leaves will start to yellow between the veins and eventually curl and eventually turn brown. Although iron may be present in sufficient quantities in the soil it may not be available to the plants. Soil pH and specific plants ability to absorb iron determine how easily iron can be absorbed by plants. Blueberries prefer acidic soils because like other plants that have evolved in acidic soils they have difficulty extracting iron from the soil when the soil pH is high. Blueberries prefer a pH between 4.5 and 5.2. If you test your soil for the pH (alkalinity/acidity) you will likely find that it is much higher than 5.2. Your soil may be even have a higher pH next to your house since there is often leaching from cement which has limestone as an ingredient. I have also seen foundations of homes backfilled with pieces of old broken cement and covered with topsoil. This increased the alkalinity of the soil and effected foundation plantings of rhododendrons which are similar to blueberries in their preference for acidic soil. In the short term you can apply a fertilizer with chelated iron (the mineral is bound to a carrier which makes it available to the plant roots even in alkaline soils). Instead of the Miracle grow you have been using it would be better to use MirAcid which has chelated minerals (like iron) especially for acid loving plants like blueberries. Long term you will need to add some form of sulfur to reduce the pH of the soil. The amount you will need to apply will depend on the difference between your actual pH and your target pH of 5.2. You can use a simple Soil Test Kit to determine your soil’s pH