Hello Fellow Readers,
I recently heard from John of Sparta NJ. I’ve heard from him periodically over the last eleven years for which I am wholeheartedly grateful. He’s been providing updates on his mother and father-in-law; my former in-laws, who I dearly love. Sadly, he shared that Dad D was in his last days.
Later he wrote, “Oh, I have a question about a tree we planted all those years ago. It’s my favorite with beautiful pink flowers in the spring. It didn’t bloom this year and has only a handful of leaves. Everything else is growing well and is in full bloom. I don’t want to take it down yet, because maybe it is just dormant?”
“I think you’re referring to the Purple Leaf Plum, (Prunus cerasifera ‘Thundercloud’)? I wrote back. “If so, sadly, many are dying due to Black Knot which looks much like its name. Once the knots are visible and plentiful it’s beyond treating. For sure it’s no longer dormant.”
John sent pictures of the screening we planted around his pool sixteen or so years ago including a closeup of the black gnarled soot-like knots coating the branches of his beloved tree. “Can it spread from tree to tree?”
“Your yard looks beautiful! I have wonderful memories of pool parties with all of you. Black Knot is contagious only between plants in the genus Prunus which includes peach, apricot or chokecherry. I’ve also seen the favored Purple Leaf Sand Cherry shrub (Prunus × cistena) with the dreaded disease.”
The fungus, which goes by various complicated scientific names that are as ugly as the disease, spreads by spores spewing from the black knots in Spring. The spores usually germinate at the joint of new leaves and form olive-green bumps the first season. They’re hard to see without close inspection. Treating the newly infected plant with a fungicide before the dreaded black galls form (a fancy name for funky growths) is your best hope. Ask your local extension office for a recommendation as effective fungicides vary by area. My go-to natural Neem Oil can inhibit the fungus from causing an infection but it won’t kill it.
If not kept in check, by year-two the dreaded black galls will form. They say you can prune and throw away the infected branches, but only in winter when the spores are dormant. Otherwise, you’ll spread the nasty fungi everywhere. Be sure to toss diseased branches in the trash in a tightly tied plastic bag and disinfect your pruners. Better yet, hire an expert arborist to assure the best chance of survival.
A magnificent alternative to John’s beloved tree is ‘Forest Pansy’ Eastern Redbud (Cercis canadensis) with deep purple foliage and bright pink blooms. Shrub alternatives include Weigela ‘Wine and Roses’, ‘Midnight Wine’, or ‘Fine Wine’. There’s my favored Smoke Bush (Cotinus coggygria) growing ten to fifteen feet. Its glorious smoke-like plumes of flowers give it its common name. Then there’s Eastern Ninebark (Physocarpus opulifolius ). ‘Diablo’, my fav, grows to eight feet though you can keep it about four feet by cutting it down to a foot high each March. All are deer resistant and have magnificent maroon foliage. Still, nothing can replace the beautiful memories of those we love forevermore.