Miss Floribunda: Tender Magnolias

Dear Miss Floribunda,

I love magnolias. I chose my house for the big white-flowered one in the backyard as well as two small pink-flowered ones in front. Spring before last the flowers on the pink ones suddenly turned brown and dropped off much too soon. This year they seemed OK, but the white-flowered one doesn’t look well: there are a lot of brown leaves; the flowers were late; and there aren’t nearly as many as usual. Do you think it is diseased? The pink ones seem to have recovered on their own. Will that last? Will the white one recover? Can you tell me what has been going on, and how much I should worry?

Magnolia Malaise on Madison Street

Dear Magnolia Malaise,

My magnolia mentor, Esperanza Sweetbay, doubts that any of your magnolias have any disease. She recalls the damage done by that sudden and unseasonable freeze in late March of 2017. Your small pink-flowered magnolias, probably Magnolia liliiflora (popularly known as a “tulip tree”) would have been blooming then. Of course, we have to guess its identity because there are over 200 species of magnolia. A much taller pink-flowered magnolia common in our area is the saucer magnolia, Magnolia soulangeana, and also fairly prevalent is the lovely star magnolia, Magnolia stellata. The flowers of these spring-blooming magnolias were literally nipped in the bud by frost and turned brown that March. Esperanza assures me that this was just a temporary setback for these deciduous magnolias and that they handle winter cold much better than do the evergreen magnolias. She assumes that the large white-flowered magnolia you mention, which would be in bloom at the time you are writing your letter, is the rather tender Southern magnolia, or Magnolia grandiflora.

Last autumn’s drought and the severe winter freezes that followed were hard on evergreen magnolias. Because your white-flowered magnolia was already well-established before you moved into your house, it is doubtless mature enough to have the deep root system needed to survive dry as well as freezing weather. Esperanza says that if you see no damage to the bark of the tree, no serious damage has been done by the cold weather, and the winter burn you report on the leaves is a temporary problem that will go away when new leaves replace the old. Because magnolia leaves continue to transpire in winter but cannot draw up replacement moisture from the frozen earth, they dry up on those bright, windy days when they get no moisture from the atmosphere. You end up with ugly brown leaves for a while.

However, owners of younger trees may see discoloration and cracking of the bark, which is an invitation to disease and pests. When the weather becomes cooler, they should apply horticultural oil to prevent insect predation. In very early spring, before the trees come out of dormancy, copper soap (copper octanoate) can be added to the oil and the trees re-treated to combat fungi and bacteria. Although using copper octanoate  is an accepted organic recourse, it can be toxic at high levels, so be careful not to use too much so that it doesn’t leach into soil or groundwater. If you have a young tree that simply hasn’t pulled through, Esperanza recommends replacing it with a cold-hardy magnolia such as Bracken’s Brown Beauty or Edith Bogue.

As for the later blooming time of your Southern magnolias, it may have been affected by the oddly fluctuating temperatures of April (going from a high of 70 degrees down to a low of 35 degrees, and back up to a high of 85 degrees in less than a week) followed by an unusually rainy May. A little light fertilizer, 5-10-5, applied next spring should promote flowering without straining the resources of an already winter-stressed tree.

Esperanza believes you have no reason to despair. In fact, the one thing all my expert gardening friends and relatives have in common is an attitude of cautious hope, bolstered by patience and good judgment.

To meet gardeners with this positive attitude, come to the next meeting of the Hyattsville Horticultural Society at the home and native-plant garden of Elizabeth and Jerry Marshall-Burgess at 10 a.m. on Saturday, July 21. The address is 3500 Taylor Street, in nearby Brentwood.  

 

Optimized with PageSpeed Ninja