Winter's Death Knell

Sudden temperature change, extreme cold, harsh winds, and lack of insulating snow are common occurrences during New England winters. These harsh conditions, depending upon their degree and frequency, have the potential to cause serious damage to plants in the landscape. Any one of these environmental factors can cause damage to plants but the wrong combination of factors can prove lethal to many diverse species of woody and herbaceous plants.

Usually winter damage does not become apparent until spring when growth normally resumes. Typically, winter damaged plants are slow to initiate growth, may show distorted growth, death of leaf and flower buds, or dieback of shoots and branches. In more challenging years, the plant species which have been damaged are often remarkably consistent across Massachusetts and the region.

Because of limited root growth, it is not unusual to see newly planted specimens die after a brutal winter. In the worst years long established plants can die, including some native species. In most cases it is species which are marginally hardy that experience the most losses.

Below is a list of plants widely observed to have died as a consequence of winter damage or have had significant winter injury (brown foliage, branch dieback, etc.) in the last several years. This list is compiled from observations by the Landscape, Nursery, and Urban Forestry team of UMass Extension:

• Arborvitae
• Boxwood
• Burning bush
• Butterfly bush
• Heathers
• Heaths
• Ilex (crenata, opaca, glabra, meserve)
• Juniper
• Lavender
• Leyland cypress
• Microbiota
• Oakleaf hydrangea
• Perennials - many species, especially silver and gray leaf species such as Artemisia and Achillea
• Rhododendrons
• Roses - Note that new shoots can appearing at the base of some heavily damaged roses. On grafted roses, these shoots can often be seen to originate from the rootstock. Therefore, the resulting roses will not be true to variety.
• Yew

What to do for those plants still alive but injured: The options for dealing with severely inured plants are limited. Basically, care at this point involves pruning out dead portions of affected plants. In addition, it is necessary to provide a good growing environment to eliminate sources of further stress. That means watering and mulching. Fertilizer is not needed. With pruning, the shoot to root balance shifts to the roots. Food reserves in roots - assuming there are ample roots that have not been winter killed - should support new growth in the remaining living parts of the shoot system. Addition of fertilizer will not influence the transport of food reserves to growing points on the shoot system.

Written by: Ron Kujawski
Revised: 09/2011