By Kirsten Conrad, Extension Agent Arlington County and City of Alexandria
The late frost and cold that Northern Virginia has experienced over the past month has resulted in damaged leaves and flowers on plants that responded to the warm spells with new growth.
Of particular concern to many are the flowering trees and shrubs, like maple, magnolia, cherry, forsythia, roses, and hydrangeas that suffered damage to new leaves and growth.
Responses to winter injury vary. Some plants will show discolored or burned evergreen needles and leaves, dead branch tips and branches, and/or heaved root systems. A simple fingernail scratch of a twig or branch surface will reveal whether there is green below the bark. If not, you can safely prune this dead wood back to a live bud.
The extent of winter damage can best be determined after new growth starts when all danger of frost is past. For most shrubs, prune the tips of plants back to a healthy outward growing bud. At this point you can cut damaged wood back to the first healthy bud. Then continue pruning to shape your plant overall. A general rule is not to prune a plant by more than a third in any given year.
A light application of nutrient rich compost or fertilizer can help a damaged plant overcome winter damage more quickly. This is also an opportunity to test your soil if you have not done so in the past three years. You can pick up a soil test form at the Fairlington Community Center or at any Master Gardener plant clinic.
Pay extra attention to plants that have had winter injury by providing adequate water and ideal growing conditions in the stressful summer months.
Although normally adapted to our climate, fruit or ornamental trees that were in flower during these extreme cold spells may have reduced flower and fruit production this year. Prune for normal structural form and correction by removing suckers, water sprouts, and dead, dying, or disarranged growth.
Tips to help prevent winter injury in future years:
- Plants known to be sensitive to extreme cold or late frosts, such as daphne, azalea, camellia, some hollies, and some rhododendrons, should be planted on the north, east, or northeast side of a building that can offer some protection from prevailing winter weather.
- Keep plants healthy and well watered. An inch of water per week is needed throughout the year. The ground rarely freezes here and we often go for many weeks without adequate rainfall.
More information about salt damage, rodent injury, and frost heave of perennials can be found at: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/426/426-500/426-500_pdf.pdf
For all your landscape care questions, consult or visit us at the VCE Horticulture Help Desk, staffed daily from 9 a.m. to noon at the Fairlington Community Center, 3308 S. Stafford St., Arlington 22206. Contact us at: firstname.lastname@example.org or 703-228-6414.