Need help!

Question: We are having serious issues with our landscaping plants. Boxwoods have many browned out areas, Cherry Laurel are infested with white scale. Rhododendron look scrawny with leaves  getting smaller and fewer and not as green as previously.  Help!!

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 April 30, 2024, 11:38 AM EDT
response: Hi,  The site conditions look challenging for the plants you have and in their planting combinations i.e. plants that prefer a little more shade and plants that like more sun and dryer soils. We can see juniper and spruce shrubs that thrive in full sun, dryer weather, and well draining soils. Boxwood, rhododenron and cherry laurel like fertile but well draining soil and prefer some afternoon shade.  1) Rhododendrons: You can review the link above for our Rhododendron Diagnostic page to learn about preferred growing conditions and common problems. They look like they are chlorotic meaning they need iron. Most of the time when rhodies are stressed with a nutrient deficiency it is due to the pH level being too high for the plants. They prefer more acidic soils. When the pH is not in the optimal range, it can cause the plant to struggle with the uptake of needed nutrients that are in the soil.  How much sun is it getting? Rhodies do best with morning sun and afternoon shade. In their native range in eastern Asia they are understory plants in wooded areas. With the Birds Nest Spruce near it we are assuming this is getting too much sun The location next to a foundation is rough for rhodies. This tends to cause the soil to be more alkaline due to the foundation. It also reflects heat off of the stone making it too hot for them. You can get a soil test done to determine the pH level and other nutrients that may not be in the optimal range, and adjust accordingly. It takes some time to lower the pH if it is needed. Or due to the sun, it may be better to relocate  the plant.  2) Cherry Laurel: You can review the link above for our Cherry Laurel Diagnostic Page to learn more about the favorable growing conditions and common problems for cherry laurel. The photo of the bare branched Cherry Laurel doesn't look like its covered in scale, but we can see some present. It does look too sparse to bring back though. We would recommend removing that one plant and any other branches on other plants that are showing scale. White prunicola scale (what cherry laurel typically get) is difficult to control with insecticides and typically we recommend pruning it out. With the cherry laurel along the foundation, we noticed that it looks like you are pruning them by cutting off the top and outer most growth or by shearing. When plants are sheared, it stimulates the outer most leaves to grow creating a dense outer growth with the sunlight not being able to reach the inner branches. This can stress the plant, lessen air flow and invite pests and disease issues. It is better to choose plants that will fit in the space when they reach their mature size as opposed to needing to prune to maintain a certain height or width. To remedy this situation now, you can thin the plants by removing some inner branches to let the light into the inner plant.  3) Boxwoods:The link above is to the diagnostic page for Boxwoods. Similarly with cherry laurel, boxwoods will get stressed when they are constantly sheared. We can't see any specific pests or diseases but the most common issue with boxwoods, especially those that are sheared is Volutella Blight fungal disease. Same as the cherry laurels, these can be thinned to help improve air circulation and growing conditions. There is no fungicide or chemical cure to cure this, but proper plant health is key. You can remove any dead or dying branches and clean up any fallen leaves under the plants to help reduce the fungal spores. Boxwoods come back easily from Volutella infections when properly pruned. Boxwoods are slow growing so be prepared to have some sparse looking plants when you prune and thin. They can rebound, but it takes time. If you don't want that in the front of your house, you could replace them and look for resistant cultivars. When pruning boxwood, you should do so in the spring preferably or at least before August so that the new growth will have time to harden off before winter. Boxwoods (and any other broadleaf evergreens like the Cherry Laurel and Rhodies) are more likely to get winter burn on the new growth that comes with pruning when a hard frost hits in the late fall/early winter. The link for Volutella has a helpful video on how to properly prune boxwoods. In general with any of these plants, we had a very dry season from Spring to Fall last year. Do you have a sprinkler system or did you supplement irrigation during that time? They could all be recovering from drought stress. Make sure to supplement water in times of drought. Mature established plants need at least 1 inch of water per week. You can feel the soil under the mulch at the base of the plants about 4-6 inches down to see if you should water. You can review our watering trees and shrubs reference page for guidance.  This is a lot of information, so feel free to go through it and ask any follow up questions.  Emily

responder: The Question Asker Replied May 08, 2024, 10:42 AM EDT
response: Thak you so much. Very informative. I have mailed soil ssamples to U of DE for analysis. One other question, the rhododendrons seems to be growiung well at the bottom of the plant, is this indicative of something?Picture enclosed.ThanksOn Apr 30, 2024, at 11:38 AM, 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 May 08, 2024, 10:55 AM EDT
response: Unfortunately the photo didn't come through.

responder: The Question Asker Replied May 08, 2024, 11:11 AM EDT
response: How is this - it is at the bottom of the e-mail.On May 8, 2024, at 10:55 AM, 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 May 08, 2024, 12:48 PM EDT
response: Sorry for the inconvenience. We still are not seeing any photo attachment on our end. We have been having some technical issues today. Maybe try pasting it in the email reply instead of sending like an attachment?

responder: The Question Asker Replied May 08, 2024, 1:53 PM EDT
response: Did this work?On May 8, 2024, at 12:48 PM, 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 May 08, 2024, 2:20 PM EDT
response: The system will not except 'tiff' files (its a nationwide program).  jpg, gif and png work well. or you can attach in a pdf or also send us a link to a google drive folder or similar cloud based storage like drop box etc. Sorry for the troubles!

responder: The Question Asker Replied May 08, 2024, 3:15 PM EDT
response: It is a jpeg. I’ll try again tomorrow.  Thanks   Frank On May 8, 2024, at 2:20 PM, Ask Extension <<personal data hidden>> wrote: