The recent temperature spikes in an otherwise cool spring have produced at least one distressing development in local gardens.
They have revealed just how damaging the winter has been on certain evergreens and on one in particular: the Southern magnolia.
Not since the deep freezes of the 1970s has so much damage been seen in these striking, glossy-leafed trees, native to the lowlands of the South. The heat of May, which induces their annual growth spurt, has also accentuated the extent of their damage. Some trees are fine, others are showing partial leaf winter burn, some are sporting dead leaves but are still alive, and many have simply perished.
The age of the tree — young ones are bearing the brunt of the destruction — and its placement are key factors in whether a tree dodged the bullet or not.
Washington is normally safe territory for Magnolia grandiflora, but the damage is a classic manifestation of the hazards of a dry fall followed by a suddenly frigid winter. A drought leaves the foliage dehydrated, a prolonged freeze locks up precious soil moisture, and a howling wind proceeds to burn the compromised leaf tissues. All these elements came together this past winter, and of those, the dryness was the worst aspect. In the final four months of 2017 — a critical period for evergreens facing the winter — we received less than six inches of rain. Normally, we get more than 13 inches.
Would watering your evergreens last fall have helped? Yes, but people don’t equate cooling weather with plant thirst. Some gardeners, particularly in the North, build elaborate burlap windscreens for their boxwood and camellias, but this isn’t practical for trees such as Southern magnolias.
In some cases, watering may not have helped. Young trees — planted in the past two or three years — still don’t have the broad, deep root systems needed to exploit limited soil moisture. And, as Phil Normandy of Brookside Gardens in Wheaton points out, the extremely popular variety named Little Gem doesn’t know when to quit for the season and protect itself by going dormant. Most Southern magnolias flower in early summer, but Little Gem — bred for its more manageable size — has been known to bloom at Thanksgiving.
Although I’ve talked to homeowners who are already ripping out their magnolias, they may be jumping the gun.
The other day, I noticed a three-year-old magnolia at Dumbarton Oaks that looked kaput, but the director of gardens and grounds, Jonathan Kavalier, told me that scraping the bark revealed green cambium — a sign that it was still alive. It may yet refoliate.
In other cases, Normandy said, the tree may suffer some partial dieback of the branches but latent epicormic buds may erupt into growth. The result will be a tree that is bushier and reduced in size but capable of regaining its place in the landscape. Normandy said owners should wait a month or so to see if the heat coaxes such growth. At that point, the deadwood can be cleanly removed.
It may take a year or two for such a tree to look acceptable — which may be too long for folks who want manicured perfection in their landscapes.
“The damage may be real, but it’s too soon to say for sure,” Normandy said. “Owners have to make up their minds. What’s their patience level?”