Blueberry Bush Spots

Question: Hello! I recently purchased and planted two blueberry plants: a Sweetheart and a North Sky. I think they were around 2-3 years old. My soil is mostly clay, which I know is not great for the plants. We added miracle grow garden soil (mixed 50/50 with existing soil) and espoma soil acidifier (sprinkled in a circle around the plant).

We watered heavily the first few days, as advised by the gardening store. The plants are not doing well. The leaves are turning red and shriveling up (see photos). Can you please advise what we can do to save these plants?

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 12, 2023, 12:29 PM EDT
response: For the future, it would be best to have a laboratory soil test performed before adding soil acidifier, as it's hard to know what amount to use (if any is needed at all) to change the pH by a certain amount. The test results can also help identify any particular nutrient deficiencies. Several brands of potting soil include time-release fertilizer in the mix, which tends to be general-purpose and not necessarily harmful to use, but it might be supplying nutrients not otherwise needed.  Blueberries prefer an evenly-moist soil but daily watering might be much more than they need, especially if the soil was largely clay-based since it retains moisture better than sandy soil types. To know when to water, feel the soil about six inches deep next to the shrub's roots (inside the root ball would be best, but is usually too hard to measure due to dense root growth). If it's becoming somewhat dry to the touch at that depth, water thoroughly; if damp to the touch when checked, the plants are probably fine as-is and can wait longer before watering.  The symptoms in the photo appear to be a type of leaf spot, though we can't determine exactly which (many leaf spot diseases are more cosmetically damaging than a serious threat to plant health, but severity varies). They can arise due to weather conditions but also due to wet leaf surfaces if irrigation hits the foliage instead of just the soil. If you can't avoid wetting leaves when watering the shrubs, then try to water early enough in the day so that the foliage has a chance to dry off by nightfall.  Fungicide use is sometimes useful in helping to prevent infections before they develop symptoms but after that point they are not curative. If you consider the use of a fungicide for next season, verify that the product label includes fruits (either blueberry specifically or fruiting shrubs) and leaf spot type diseases. Follow all label instructions and be aware that several repeat treatments per year will likely be needed. Having said all of that, though, blueberries do not usually require as intensive of a preventative disease management program compared to fruit trees. Heavily-infected individual leaves can be clipped off but we'd hesitate to recommend this if the plants are quite young and don't have too many leaves to spare, as this might weaken them further.  We have several web pages about blueberry care and troubleshooting if they are of use going forward. If the symptoms worsen and spread to currently-clean leaves, feel free to send us new images of both the leaf top and undersides, along with an image of the plant's growing conditions (the site where they're planted so we can see plant size, spacing, etc.), if possible. For now, just monitor their watering needs and pull the mulch back a couple inches from the crowns (the place where stems emerge from the soil) if it's touching the stems, as this reduces air circulation and can invite other disease issues. Any leaves that might fall off the plant due to infection can be collected and thrown out (don't compost).  Miri

responder: The Question Asker Replied June 14, 2023, 8:13 PM EDT
response: Thank you very much for all the information. - I have drip irrigation installed. - Soil test previously showed a pH of 7.4. I know this isn't good for this plant, but my 6 year old son was insistent on blueberries. - Attached are new pictures. Thank you, DanOn Mon, Jun 12, 2023, 12:29 Ask Extension <<personal data hidden>> wrote:

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 15, 2023, 3:18 PM EDT
response: Hi- thanks for the additional photos. Overall, the plants are in decent shape for being recently planted. All plants go through a period of transplant shock as they get acclimated to new conditions and begin to establish a root system.   Blueberry plants take longer to establish than other small fruit plants because they are more sensitive to less-than-ideal soil conditions (including high soil pH) and their roots don't have root hairs, limiting water and nutrient uptake in young plants. The reddish-brownish leaf discoloration is a common blueberry stress symptom.  While there are a number of leaf diseases of blueberry we think the symptoms in the photos are caused primarily by environmental stress.   1. Keep the plants well-watered during dry periods this summer and fall 2. No need to remove discolored leaves 3. Apply a complete fertilizer (contains nitrogen, phosphorous, and potassium) if leaves become light green in color and new growth is slow. (Blueberry grows best with the ammonium form of nitrogen, rather than the nitrate form.) 4. Remove any flowers and fruits that form to direct the plants' energy into root growth 5. Take and submit a soil sample (in our first response) this fall and buying and apply ammonium sulfate fertilizer (21-0-0) next spring when flowers first open. Jon