Green and Growing: When evergreens turn brown, what do you do about it?
It’s way too soon to dig gardens or apply fertilizers, but plump magnolia buds and bright yellow willow branches invite us to one of the first steps in spring land care. It’s time to inspect woody plants for winter damage, diseases and insects.
According to Jeremiah Green, an arborist with The Care of Trees, an affiliate of the Davey Tree Company based in Hamden and Norwalk, a lot of people call their offices about evergreens this time of year.
“They see browning on the needles and worry the tree is dying,” Green said. “In reality, some browning is completely natural — while other times it’s a cause for concern.”
He says that winter weather makes it difficult for evergreen trees to supply their needles with enough water, which leads to drying and browning. Most evergreens naturally drop some needles in fall and winter.
“White pines, for example, drop about one-third of their needles during the dormant season. That’s their cycle,” he said. “But if you see an entire side of the tree turn brown, and it is in direct sunlight or has a lot of wind exposure, the tree may have winterburn.”
Winterburn results when intense winter sun heats needles and leaves above the ambient temperature, and it can affect broadleaf evergreens such as rhododendrons and boxwoods as well.
If the needles or leaves are already dry, the problem is worse. Damage usually appears on the southwest side, where sun is hottest. Sometimes only the tip of the needle turns brown while the base remains green.
Prevention of winter damage begins in the prior growing season, according to Green.
“Keep trees evenly watered throughout the growing season and into the late fall, particularly young trees,” he said.
As for expensive or highly visible landscape plants, “Anti-desiccants can be helpful. They put waxy coating on leaves, which helps shield leaves from moisture loss.”
Green says people often call this time of year about spruce damage, particularly Colorado blue spruces.
“The tree is native to high altitudes and a drier climate,” he said. “Outside of its native range, it can get a disease called cytospora canker.”
The problem appears as cankers on the on the lower limbs and trunks, accompanied by white sap droplets. The lower branches lose needles and die in an irregular pattern. “There’s no treatment for cytospora other than encouraging the overall health of the tree,” he says. Early identification makes a difference.
March is also a good time to look for insects.
“Some signs include small holes in the bark and sawdust in the branches and on trunks,” Green said.
He recommends the use of “spring dormant oil,” a name that refers to the dormancy of the plants, not the oil. This horticultural spray can reduce the populations of spider mites, aphids, scales, several types of adelgids, lace bugs and more.
“It’s an old practice that has stood the test of time,” he said. “It has extremely low toxicity and it doesn’t hurt beneficial insects because, for the most part, they haven’t emerged yet.”
Green’s definition of good tree care includes the possibility of selective pruning to remove dying branches. A steady water supply makes a big difference, especially to young trees.
It is helpful to keep lime and lawn care treatments separate from tree areas. Lime raises pH, which is good for grass but not for most of our regional trees. Lawn fertilizers can burn the roots of young, newly planted trees.
It is also helpful to spread one-half inch of finished compost under branch drip lines, and cover with two to three inches of mulch. No mulch or compost should ever touch the trunk.
“Pine needles or leaf litter are great sources of mulch,” Green said, “but not gravel, rubber or dyed mulch.”
Gravel adds no organic matter, and according to Green, dyed mulches sometimes have a lot of termite pesticide, which can be bad for the trees.
If you decide to get help with pruning or spraying, remember that arborists are licensed in this state. The Connecticut Tree Protective Association provides a searchable database as well as a list: ctpa.org/find-arborist/.
Kathy Connolly is a landscape designer, speaker, and writer from Old Saybrook. Contact her or view her speaking schedule at www.SpeakingofLandscapes.com
Making the proper cut
Early March is ideal for pruning trees and shrubs because the cuts can heal before pathogens become active in spring and summer. This is an especially good time to prune non-flowering deciduous shrubs and shade trees such as maples, oaks, and elms, as well as summer-flowering species such as Rose-of-Sharon, viburnums, and summersweet. It is also a fine time to prune needled evergreens.
If you never got around to pruning your bigleaf or oakleaf hydrangeas last year, however, don't do it now. Bigleaf hydrangea (Hydrangea macrophylla), mountain hydrangea (H. serrata), and oakleaf hydrangea (H. quercifolia) all form flowers on last year's wood. You'll be taking off 2018's blossoms.
Also skip other spring-flowering species for now, such as azalea, rhododendron, magnolia, forsythia, chokeberry, and lilac. Prune these after they have finished flowering, usually by early June.
If you feel uncertain about how to make a proper cut, Connecticut College Arboretum will offer a two-hour lecture and demonstration by pruning expert Jim Luce on "The Art and Science of Pruning" on Saturday, March 31, 10 a.m. to noon at New London Hall, Classroom 101, Connecticut College. Luce covers what, when, how and why to prune. See www.conncoll.edu/the-arboretum/programs-and-activities/ or call (860) 439-5020.
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