I got a call yesterday from someone who was puzzled about some shrubs that weren’t doing well. She called them “cherry laurels” (Prunus laurocerasus) and said that they looked dead. She’d consulted area landscapers and master gardeners, and had gotten so many opinions about these plants that she didn’t know what to do. One person said they had a fungus and they needed to be ripped out, while another suggested that scale was the culprit.
After asking her if the entire branches looked brown and dead (“No, just the leaves.”) and if there was any sign of the dark grey powdery sooty mold on the lower leaves or stems that would indicate a scale infestation (“No, they are either brown or green. No sooty mold.”) I told her what I thought. “I’d bet money that these plants just have winter damage,” I said.
Why would I make that call based on a phone conversation, without seeing the plants? Because that’s what cherry laurels in this area do on Cape Cod. I’ve had a number of these plants, from the upright “skip laurels (Prunus laurocerasus ‘Schipkaensis’) to the low-growing ‘Otto Luyken’ and they are prone to two problems: shot-hole fungus and winter burn. In the early spring these plants can look like hell.
Had she come to me with this description of her cherry laurels in July or August I would have been perplexed and wanted to see the plants, the pattern of the browned leaves (all over the plant or just one side?) and the area where they were growing. Because browned leaves in the summer would be unusual for this Prunus. But at this time of year, we can be 99% sure that it’s winter burn because that’s just what these plants do.
I advised her to wait and watch. If I’m right, her plants will drop these burned leaves in May and by early June they’ll be covered with fresh green shoots. At that point she can trim off any stem tips that have remained black with die-back.
I still like this plant – especially the short variety, ‘Otto Luyken’ because it grows well in shade and is a useful plant for foundation plantings that can’t grow too high. In areas that are protected from winter wind and winter sunshine they get less burn.
Note: The shothole fungus can be pretty well controlled by making sure that the plants aren’t hit with a sprinkler too frequently. It can be worse in a season that’s extremely wet and cool, but I find that most often this problem shows up when an automatic sprinkler is set to go off too often.