Living in a climate with cold winters can wreak havoc on your garden. But air temperature is not the only worry during winter. The amount of precipitation and humidity also factor into whether a plant survives or dies in frigid weather. During cold, dry windy winters, plants can be injured or die from desiccation. Winter desiccation occurs when the absorption of water by the root system cannot keep up with the amount of moisture lost by the foliage (transpiration) - in essence the plant is being freeze-dried. Conditions are most ripe for desiccation on sunny, windy days when soil water is frozen and the plant cannot absorb it.
The combination of cold and dry is especially stressful for broadleaf evergreens, like rhododendrons, and for trees with thin bark such as birch and silver maple. So steer clear of these if your property is prone to drying winter winds. But there are plants that can survive these conditions. A great perennial shrub for dry cold locations is Yucca harrimaniae (Harriman’s Dwarf Yucca). A strong, stiff-leaved plant, yuccas provide a bold architectural accent in the garden and will reward the gardener with upright flower stalks come summer that can reach four feet high. But don’t plant yucca if there’s a chance the soil will stay wet; it’s a sure way to quick death for this one.
A good perennial plant choice for cold & dry areas are the Eryngiums, or Sea Hollies. Amethyst Sea Holly (Eryngium amethystinum) is a particularly nice variety. A well-behaved border-sized perennial, it stays where you put it and never fails to elicit inquiries from garden visitors curious about its unique blue-toned, star-shaped flowers and bracts. Deep roots make it tough and care-free. The blooms are long-lasting, and it makes an excellent cut flower that also dries quite nicely.
Once established, Eryngium doesn’t like to be moved, so plant it where you want it to stay. A cover of loose evergreen clippings around the base will help protect the plant from wild temperature fluctuations without hampering air circulation.
If you’re stuck with plants that are prone to desiccation, you can give them a helping hand by making sure they are well supplied with water in the fall and early winter. Burlap screens and windbreaks can be used to shelter susceptible evergreens. Spray antitranspirants, or antidesiccants, can also provide some protection by reducing the amount of moisture lost by the plant. Be sure to follow all label directions carefully if you choose to apply chemicals.
If cold and wet is the winter forecast, the plant selection strategy is a bit different. Don’t confuse a wet winter with heavy snowfalls – though a large snow accumulation followed by a quick thaw can result in water-logged soils and subsequent root rot. If snow arrives after the ground has already frozen and air temperatures are stable; it can actually serve as an insulation layer that stabilizes soil temperatures and minimizes the chance of soil heave. This sends plants into a restful dormancy where they can remain until Spring wakes them up better than ever.
But long-range forecasts for our area included in the National Climate Assessment indicate more winter precipitation will fall as rain rather than snow through the end of the 21st century. With this in mind, it makes sense to choose plants that can tolerate cold, wet winters. However, it is important to remember that few, if any, plants can tolerate wet "feet" for prolonged periods. If you have any area in your garden that is particularly slow draining, it may make sense to rethink planting there altogether. Plants that are oversaturated with water tend to have shallower root systems and generally fail to thrive. In addition, wet soils take longer to heat up in spring than well-drained soils, so your garden may bloom later than normal during cold, wet winters.
Yet, there are some plants that can make it through a cold, wet winter. Cornus stolonifera (Redtwig Dogwood) is a great shrub because of its bright red branches and ability to handle wet soils. Not only does it bring a bright spot to the winter garden, but it’s nice in indoor seasonal arrangements as well. In the perennial category there are a few good choices. Polygonatum humile (Dward Solomon’s seal), Iris siberica (Siberian Iris), Dictamnus albus (Gas Plant) are some of the hardiest ornamentals in our area.
The winter garden, whether cold and wet or dry and windy, offers challenges for even the most determined gardener. But with careful selection and thoughtful site placement, even the dreariest landscape can become a thing of beauty come Spring.
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Linda Spellman
