Plants Burned by Our Weird Winter
Exactly 30 years ago, Washingtonians awoke not so much to a silent spring in the garden as a morbid one. As the season warmed after a bitterly cold winter, it became apparent that a lot of evergreens were browning and many would not recover.
In Georgetown, which is one of the most sheltered spots for plants in the city, whole rows of southern magnolias withered and died. Across Washington, virtually every camellia perished, even the oldest, hardiest ones.
The spring of 2007 is not a repeat of that floral shambles, but there are some disturbing echoes of it. Look hard at your hollies and cherry laurels, and you will see a lot of leaf damage. Young nandinas have been virtually defoliated. Leaf burn is particularly noticeable on shrubs that are supposed to look their best with the fresh spring flush. This year, red-tip photinia should be renamed brown-tip photinia. Japanese camellias are putting on a brave show of blooms, but the flowers are displayed above wretchedly burned foliage. Southern magnolias are heavily marked by leaf burn, mountain laurels are browned and spotted, and some boxwood has been rendered dead.
These maladies are not linked to the unusual and prolonged late freezes that have occurred this month -- that phenomenon has caused its own and different woes. The freezes have caught off guard the home gardeners who jumped the gun with such plantings as basil, tomato seedlings and tender annuals. The nursery trade has suffered its own losses from these freezes, as the frost has marked new and tender growth. And apple and peach losses are predicted to be dire this year.
Evergreens -- broadleaf shrubs such as rhododendrons and needled trees such as pines -- take their chances every winter and run the risk, ironically, of drying up. This happens when the ground freezes, winter winds whip up and the plants cannot replace the moisture that is lost from the leaves. Normally in November and December, the weather gets steadily colder, so that the trees and shrubs toughen up for what lies ahead in the depths of January and February. But this year, the weather stayed mild, and that hardening-off didn't occur sufficiently. This left foliage ripe for latent damage when February turned stubbornly frigid.
The freakish January also coaxed spring bulbs into early growth. The blooms were not affected, by and large, but there has been a lot of unsightly tip damage on such spring bulbs as snowdrops, daffodils, snowflakes and tulips. I felt sorry for my wood guy, who called in January asking if I would take another cord, and I had too much left unburned. When I told him this, there was the sad resignation in his voice that betrayed all the other calls he had made that evening, and the ones he was about to make.
Just because deciduous plants have the sense to lose their leaves in winter, they are not out of the, er, woods. In quirky years like this, you may see splitting on thin-barked trees such as maples, sycamores, lindens and zelkovas. In winter, when you get extremes of day and nighttime temperature, the stem tissue expands and shrinks, "and you get the sap freezing within," said Kevin Carr, a certified master arborist with Bartlett Tree Experts in Rockville.
The result can be a vertical split anywhere from six to 24 inches, especially on the south or southwest side of the trunk facing the winter sun. Carr said he had not seen this yet but expects to between now and Memorial Day. Young trees are vulnerable, but mature trees are candidates for this, too, and if a large fracture appears on a big tree, its owner should get an arborist to see if it poses a danger of breaking up, said Carr. On smaller trees, frost cracks often close as the tree grows, but in cases where the bark has peeled, the flap should be removed with a sharp knife, said Carr.
An injured tree should be adequately watered and fertilized to promote vigorous regrowth this spring. The good news is that an up-and-down surface crack on a trunk is not as deadly as a girdling wound, which can destroy the entire vascular system.
As for fixing the leaf burn, the keyword is patience. If you run out and trim off everything you deem ugly, you will remove secondary buds that would otherwise burst forth next month and begin to mask the damage. The plants themselves will soon shed badly damaged leaves.
Certain plants that have growth from suckers, such as nandinas and mahonias, could have selected stems removed at ground level, but I would wait to see what regrows first.
What all these plants would benefit from this spring is a two-inch mulch of screened compost and some watering if the imminent heat is coupled with dryness.
Next fall, let the trees and shrubs harden off by not pruning and not feeding them in late summer. Water them well in November, barring flood. Shrubs and modestly sized trees can be sprayed with a coating called an anti-desiccant, which will reduce wintertime moisture loss.
The ratty leaves are just part of an unsatisfying spring that so far has been marked by cold temperatures, tempests and flowering fits and starts. Things will settle down, and soon our baskets will be overflowing. The memory of this winter will soon pass, even if the recollection of the one three decades ago has left us a bit scarred.