Boxwood problems

Question: Last summer my wife and I bought an older home and moved to  Laurel.  In the fall we noticed some of the boxwoods looked like they were not doing well compared to others.  All are big plants, likely many years old.  There has been no improvement this spring.  I'm wondering what the problem is and what to do about it.

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 27, 2023, 12:15 PM EDT
response: Hi,  For older boxwoods you could do a regeneration prune to thin out and remove some of the old dying growth to help regenerate some new growth and vigor. If they are been sheared in the past (it does look like it from these photos), it only stimulates the end growth of the plant and causes them to develop thick outer growth , not allowing light and air movement to the inner branches which can cause die back and disease issues. The orange color is usually from winter damage and fluctuating winter temperatures. The branches with the straw color should be pruned out all together. You can explore our Identify common Boxwood problems webpage to see if you can explore other issues. There is also a link at the bottom of the page for a YouTube video on the pruning techniques to help thin them out and get rid of the damaged stems. If there are any specific disease issues, proper pruning tends to be the best solution for maintenance anyways, unless you see other telltale symptoms.  Feel free to continue to send photos or reach out with other questions.  Emily

responder: The Question Asker Replied April 12, 2024, 3:03 PM EDT
response: Hi Emily It’s almost a year later now.  The boxwood problem seems to me to be spreading to other boxwoods…I probably have between 18 and 24 Boxwoods total.  I’m wondering if there is someplace in the area where I could take or send more pictures of some of the yellowing or whitening vegetation.  If it is the boxwood blight apparently the only thing to do it dig out every one that is yellowing.  I’d hate to lose them all but don’t know what to do.  I live in South Laurel.   Thanks for your any help you can give me. John

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 12, 2024, 5:46 PM EDT
response: Hello John,  You are welcome to share photos here, in this discussion thread; while the system might limit you to three attachments per reply, you can reply more than once in order to send more pictures if needed. If you prefer, you might be able to bring samples in to your local county Extension office, but reach out to them ahead of time to see if they can do such a diagnosis. (Sometimes, county offices just send the inquiry to us at Ask Extension if they don't have a horticulture specialist or plant pathologist on-site, since we at HGIC are not based in a county office, but answer queries from around the state.)  One of the most common ailments we see on the myriad boxwood questions we're sent throughout the year is the fungal disease Volutella Blight. Like many plant infections, its severity and spread can be weather-dependent, more severe in wet conditions when rains are regular or when plants are irrigated often (or with sprinklers that wet the foliage). Volutella is a comparatively weak pathogen, meaning that it largely takes advantage of struggling plants that are stressed from some other cause (like winter damage or over-pruning), and it tends not to cause damage on healthy plants. Since this fungus does not kill the roots, a drastic cut-back like Emily had mentioned is often the best recourse, especially since pruning out dying branches would otherwise leave a patchwork of unappealing scraggly stems. A photo example of a pruned-back boxwood shrub that has begun to regrow is attached, if helpful. Granted, given the slow growth rate of boxwoods, it will take a few years to regain its former size, but if the shrub is not sheared in the meantime, it probably will be less vulnerable to future Volutella infections or other issues because the foliage won't be as crowded.  Boxwood Leafminer is the other problem we see very frequently, and high populations can cause a lot of foliage discoloration (turning orange-yellow), blistering, and premature leaf shedding. If this pest is present, the bright yellow-orange adult gnats will probably emerge fairly soon and hover over the plants. (They don't bite.) On a quiet day in spring, you might even be able to hear the shrub rustling (like the subtle popping of wet Rice Krispies) with the activity of the juveniles while they are still inside the leaves. Heavy pruning, as for Volutella management, will also help remove the majority of these insects from an infested shrub. Some boxwood cultivars are more inherently susceptible to this insect than others. Some insecticides work well for management of this pest, but we generally discourage their use since they might impact beneficial insects.  Boxwood Blight is less likely if the ailing plants have discolored foliage like you describe, since usually an advanced stage of infection results in no foliage (they shed pretty quickly, sometimes while still mostly green) and a very bare, twiggy appearance, especially in large sections of the plant, or starting around their base. If it is present, then yes, replacement with non-boxwood alternatives is the most practical solution.  Miri

responder: The Question Asker Replied April 18, 2024, 5:39 PM EDT
response: Thank you, Miri, for your help.  If you think it would be of any value, I’d be happy to take two or three pictures and post them.  John

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 18, 2024, 6:32 PM EDT
response: Yes, if you are unsure about a diagnosis based on the information and images included in the links sent previously, sharing photos will help us narrow-down what might be going on with your plants. Images of the overall shape (health/appearance) of the plants as well as clear close-ups of any distinct symptoms will help. If you need to send more than three files and the submission form limits you to three, simply reply again and attach more images as needed.  Miri

responder: The Question Asker Replied April 19, 2024, 10:41 AM EDT
response: I have taken three pictures but can’t spot the link for sending them.  John

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 19, 2024, 11:02 AM EDT
response: You can either paste them into the body of your reply, or attach them in the same way you did earlier (there should be a "choose file," or similarly-worded clickable function, at the bottom of the place you type your reply). It might be easier to find if you're answering in Ask Extension itself, when you click on the link to the question thread in the email the system sends you with our responses.  Miri

responder: The Question Asker Replied April 19, 2024, 1:59 PM EDT
response: Attached are three photos of the boxwood bushes that are affected.  Thanks for taking a look.  John

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 19, 2024, 3:11 PM EDT
response: Hello John,  Thank you for the photo. (We received the file name ending in -58. The other two files, ending -19 and -45, must have been too large as-is, according to the error message seen on our end.)  The orange foliage is normal during winter for many cultivars of boxwood, but not that normal this time of year since we've had multiple warm days now. If widespread and not limited to just a few branches, an orange flush to the leaves suggests the entire plant is stressed enough that it might not recover well. Perhaps the root system was damaged by soil wetness or drought in a prior year, or the plant is succumbing to an opportunistic infection like Volutella. While Volutella can't be treated with fungicide, often it can be pruned out to trigger the shrubs to regrow and recover.  It's hard to determine an exact cause when it might have begun in the fall of 2022 or earlier, when you first noticed it. The history of the plant being unknown (did the prior resident make any changes to the drainage patterns in the area, or water them more than they should have? did any utility digging or other activities harm roots? were there voles in that part of the yard, chewing on main stems or tunneling through root zones?), it's hard to guess what began the decline. If one of the missing photos shows the entire planting area (or most of it, anyway, for several of the ailing shrubs), that might help us narrow-down potential causes.  We don't see indications in this one photo of Boxwood Leafminer or Boxwood Mite, but on leaves this color, their characteristic damage traits would be much harder to see. The orange flush is not a symptom of Boxwood Blight.  Miri