Viburnum damage

Question: Hi - I have a new viburnum that has started showing sun burned leave (what I think it is).  The tree is new this season, gets watered regularly.  I do not see any pests on the plant.  Is what I am seeing, sun burn or heat stress?

Thanks for your 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 August 29, 2024, 12:09 PM EDT
response: Unfortunately your photo didn't come though for some reason...can you please resend it?  Scorch, which is leaf damage from dehydration and high temperatures, is certainly possible. You mention that it's being watered, which is good, though both under- and over-watering can lead to issues like scorch and similar symptoms. When the Viburnum was planted, were the roots loosened well after removal from the pot? If not, it might be struggling to establish, which means that roots might not have access to enough moisture, or that watering will be harder to monitor since the potting mix inside the root ball is quite different in moisture retention and drainage than the surrounding soil. (These get blended together better when root balls are disentangled well, or even bare-rooted, prior to planting.)  When monitoring for watering needs, make sure the soil is being checked to avoid over-watering by accident, especially since symptoms like wilting are unreliable and can be associated with over-watering as well as under-watering. Feel the soil about six inches deep next to the root ball, and water thoroughly once it becomes somewhat dry to the touch at that depth. (If the soil is damp at that depth when checked, watering is probably not needed, though different Viburnum species have different tolerances for soil wetness.)  Miri

responder: The Question Asker Replied August 29, 2024, 3:41 PM EDT
response: Response to Miri.  I am sorry the pictures did not come through.  I hope this works

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 August 29, 2024, 5:06 PM EDT
response: Thank you for the photos. This looks like a bit of scorch combined with some leaf spot infection(s). Any leaf spot present is minor and doesn't need to be addressed (nor would a fungicide provide much benefit this late into the growing season), but the more extensive portion of the leaf damage appears to be from scorch. Make sure any turfgrass or weeds are kept away from the base of the main stem(s) so trimming or spraying them does not harm the bark, as cuts injuring sapwood can be fatal to shrubs and trees. A mulch ring around the plant is a good way to protect it from competing plant growth or mower injury (if you were to string-trim inside that wire cage, for example), though keep any mulch layer only about 2-3 inches deep at most, and don't let it touch the bark so it continues to get good air circulation.  Miri