Conifers Gardening Laidback Gardener Tip of the Day

Preventing Winter Damage to Conifers

Dwarf Alberta spruce (Picea glauca albertiana ‘Conica’) is so susceptible to winter damage it rarely makes a good choice for laidback gardeners.

If conifer needles sometimes turn brown at the end of the winter, it’s not usually because of the cold (most are very hardy!), but rather because they dried out. Since most conifers hold onto their needles year round, they continue to lose water to transpiration even in the winter. This kind of winter burn tends to occur in windy sites and especially on the south or southwest side of the plant. That’s because not only does constant wind tend to dry the needles out, but when sunlight warms the needles during the day on the sunny side of the plant, even more water is lost to transpiration.

Fortunately, most of the time, the plant recovers from this type of damage quite well. New needles grow back in late spring from dormant buds and, by summer, you can scarcely see any damage. Still the browning effect can be visible for several months in the spring. Isn’t there anything you can do to prevent it?

An Ounce of Prevention

To help avoid winter damage, water conifers in the fall just before the ground freezes. That’s because, if the plant’s cells are well irrigated, there is more moisture for the needles to live on. If ever there is a mid-winter thaw, to the point where the soil thaws out, get out there and water your conifers again, as the roots will be re-activated and looking for moisture. Finally, when spring does finally come around, watering your conifers yet again as soon as the soil thaws will help them to regenerate more quickly.

It is also wise to mulch the soil around conifers planted in windy sites. This allows their roots continue to absorb water longer in the fall and thus helps reduce or prevent damage.

A simple screen is all it takes to protection young conifers for the first winter.

Note also that newly planted conifers are more prone to winter damage because their root system is not yet well established. It can be wise to surround new conifers with burlap or agrotextile for their first winter. Of course, don’t forget to mulch them too.

Salt Spray

Salt spray from de-icing salt can burn the needles of nearby conifers.

Conifer needles can also suffer winter damage from an entirely different source: salt spray from de-icing salt. This will generally only occur near busy roads where road salt is used. And the busier and faster the traffic, the further the damage will spread, because droplets of salty water will be thrown far and wide. Salt can then accumulate on the plant’s needles, absorbing the water within by osmosis, thus causing the needles to dry out and die.

Since this problem returns year after year, the simplest solution is to plant only salt-resistant plants near roads… and conifers are usually not good candidates for such positions. Ideally, near roads treated with de-icing salt, you would use only low-growing plants that will be covered in snow all winter, like perennials, bulbs and groundcovers, or deciduous trees and shrubs known for their resistance to salt spray, as barberry (Berberis thunbergii), rugosa rose (Rosa rugosa) or sea buckthorn (Hippophae rhamnoides).

White pine suffering from salt damage.

Among the conifers that do show a certain resistance to salt spray are white spruce (Picea glauca), Colorado blue spruce (P. pungens), junipers (Juniperus spp.), larches (Larix spp.), Swiss mountain pine (Pinus mugo) and Austrian pine (P. nigra). Conifers that really can’t handle salt spray at all include white pine (P. strobus), yews (Taxus spp.) and arborvitae (Thuja occidentalis).

Over-diligent gardeners install all kinds of structures to help protect their conifers from salt spray every year, but the laidback gardener can avoid all the hassle by simply not planting conifers under conditions that don’t suit them or transplanting them to a more appropriate spot if you do make a mistake. That can mean at least 30 feet (10 m) back from the street in the case of a truly busy road.

The right plant in the right place: it always has been and always will be the best way to go!

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