Spotlight on Snow Part 2: The Joys and Challenges of Snow in the Garden
This is the second post in a two-part series exploring the topic of snow in cultivated and natural landscapes. Diving deep into the many ways we relate to snow in our lives gives us inspiration for landscape designs that work with the natural elements and processes of the earth. Some important qualities of snow are described below that relate to how we see it and experience it, deal with it, play in it, and how it fits into the ecology of the surrounding landscape.
The Super Powers of Snow Crystals
Insulation from temperature swings
Thick, fresh, fluffy snow will insulate the soil and your plants from sub-freezing temperatures. This is because of the air trapped in between the ice crystals in freshly fallen snow. Each inch of snow has an average R value of approximately 1, and the insulation value increases with depth of snow. So as the air temperature drops far below freezing point of water, the snow is holding in earth’s radiant heat in the soil, keeping the ground from deep freezing. This protects the roots of perennials, and biennials and shallow bulbs. However, as snow melts and compresses, much of the insulative property is lost as air pockets become smaller or filled with liquid water, and becomes more “slushy” snow.
Absorption of Sound
The experience of quiet in a snow-covered forest is difficult to replicate. The sound absorbing quality of fresh snow takes the edge off of harsh noises, and envelops one in a sonic cocoon of stillness. Meanwhile, the chirps and calls of nearby songbirds sound clearer and more crisp with less sound pollution. This is because of the roughness of the surface of the snow and the trapped air inside the structure diminishes vibration. While this quality of snow has less direct application to the garden, I find it fulfilling to take note of the subtle changes in my surroundings when experiencing connection with nature, and working with these experiences to inform creating new spaces with similar qualities that we find important. Stillness, calm and quiet are values that promote wellbeing and healing, which can be promoted in landscape designs by creating areas of sound isolation using surface roughness provided by natural structures. As the snow surface melts and refreezes, sometimes a layer of smooth ice can form on the surface of snow pack. This has the opposite effect on sound behavior and results in increased echoing as sound travels farther.
Infiltration and Storage of Fresh Water
Because of the insulative properties of snow, it often takes a long time for snow to melt, even a while after temperatures remain above freezing. Slowly melting snowpack allows time for a large volume water to infiltrate deep into the soil, recharging aquifers which are the long term storage areas of underground water. The same amount of water falling as rain might otherwise run off quickly over the ground surface rather than soaking in. The amount of water infiltration and aquifer recharge varies by soil type, surface compaction, and weather conditions prior to the snow cover. Slowly infiltrating water from deep snow pack allows nutrients in the soil surface time to dissolve in the water, and to percolate down into the root zone, where active transformation and uptake of dissolved minerals and nutrients occurs.
In places with high elevation mountains with year-round snow pack, the storage of fresh water in snow and glaciers is crucial for maintaining the flow in rivers, bringing live-giving hydration in times of drought. In springtime, rapid snow-melt combined with spring rains will fill rivers to the brim and flood low lying areas. This seasonal flooding from snow melt brings the essential nutrients and fine silt deposition that over aeons have built up rich soils that support agriculturally productive lands.
A Feast for the Eyes
Snow covered forests are quite striking to see as the stark outlines of trees and protruding rocks and stand out in contrast.
This showcases plants that have special structural features, such as shrubs that retain their berries, unique colored or textured barks and fun shapes such as corkscrew and weeping cultivars. A few trees and shrubs that look amazing the snow are river birch (Betula nigra) with its multicolored flaky bark, winterberry holly (Ilex verticillata) the females are heavy producers of bright red berries that persist through the winter, Harry Lauder's Walking Stick (Corylus avellana 'Contorta') a funky filbert-nut cultivar, and red-stemmed dogwood (Cornus sericea) which is remarkably self-descriptive. Placing sculptural landscape elements such as boulders, yard art, benches or bird baths in highly visible locations will enhance the beauty of the garden year-round
Harry Lauder's Walking stick, red-stemmed dogwood, and a female winterberry holly
Tracking and Surveying
Finding tracks in the snow is exciting, and tells you about who is showing up in your neck of the woods when you’re not around. You might be surprised to see stray cat or dog or even chicken tracks in places you didn’t expect. I like the little stories they leave behind. You may notice the tracks of a predator, or a fresh pile of scat or urine discoloring the snow.
Reading the landscape during snow cover is a unique opportunity. The snow helps to knock down the dried standing stems of tall field herbs and grasses, leaving behind a sharper surface that makes it easier to see the concave and convex curves of the earth. The humps and bumps of this plain white surface has an aesthetic with its own unique and ephemeral beauty. As snow melts, it’s easy to see the places that stay cooler longer as big chunks of snow get left behind. And its informative to see where ground water upwellings spring out of the soil. The warmer ground water melts the snow in its wake as it leaks from earth’s crevices.
The lightness and darkness of a surface affects how that surface absorbs light energy; a quality called “albedo,” which in case you were wondering definitely rhymes with libido. Snow cover reflects the light of the sun back into the cosmos, which on a grand scale is important enough to effect global temperatures. Conversely, dark surfaces, such as areas that have been burned, dark humusy soil, or a sheet of black plastic, absorbs sunlight which then radiates heat back and also affects air temperature on a microclimate scale. The snow can reflect light into your windows at home helping to brighten things up during the darkness of winter. You may find that this helps out your indoor plants, and improves your general mood.
Snow, the Great Concealer
I used to live in Vermont where objects could become buried under the snow in November, and end up lost to the world until April under a continuous cover of snow pack. Each spring would reveal the exciting assortment of curiosities, ephemera and discards of society. Typically, one might find missing gloves, hats, notebooks, wallets, food wrappers, dead animals, jewelry, toys essentially an entire winter’s worth of buildup. Taking this lesson home to the garden, it’s easy to lose track of stuff like say, garden tools, if left outside in absent minded fashion. Hidden rocks, stair steps, hoses, and misplaced tools can become major tripping hazards under just a few inches of snow. Be sure to organize and prep your outdoor spaces prior to a big snow to avoid these kinds of surprises!
The Subnivean Zone
A few animals take advantage of the hidden world between the snow and the surface
of the ground. In thick snow cover, the snow immediately next to the ground surface can melt or sublimate (water evaporating directly from ice) leaving behind a pocket of space in between the ground and base of the snow pack. This is called the Subnivean Zone. Here small animals can take advantage of the refugia created by all the unique protective properties of snow (for example its insulation and sound absorption properties) and stay hidden from predators like foxes and owls.
Voles and mice can forage for grass, seeds and chew on the bark of shrubs with relative safety under snow, but can still be vulnerable to attack from weasels and shrews who also utilize the Subnivean Zone. So don’t be surprised if you see damage from rodents at the base of your woody shrubs and young trees after a long and deep snow cover.
Heavy Weight Champion
All that frozen water piling up in one place can do major damage to tree limbs especially of evergreen species whose leaves hold on to more of the white stuff. Dramatically bending out of shape is not uncommon, and fascinatingly branches have the ability to spring back into place after the snow load melts if they don't succumb to breakage.
Other structures in the garden are at risk for collapse, especially delicate plastic row covers, and greenhouses. It’s important to know how much weight your structure can handle, and be diligent about removing the snow loads if they get to be too much. Insulation provided by snow cover can be an advantage, but if your structure collapses you’ve got a much bigger problem than frosty leaves. Therefore its important to brush snow off of these structures if possible during long and heavy snowfall events to prevent disaster. Or, build structures with the strength to support anticipated loads, or that are designed to shed snowfall with steep pitched roofs.
You are a unique snowflake! Similarly, there is infinite diversity in how snow falls and accumulates! Depending on precedent temperature, moisture, wind and post snowfall conditions, a lot of snow types are possible, and behave differently. The microstructure of snow affects its porosity, density and surrounding conditions affect how the snow settles and builds up. The following table describes a comprehensive list of snow types and formation conditions, and ranks snow types from lightest (least dense and more air trapped) to heaviest (more dense and less trapped air). One could reference this table to estimate the weight of snow that might be on a structure with a little mathing and a few basic assumptions about the snow type and depth.
When it's not snow anymore...
When snow melts, and then refreezes, it is transformed from mystical wonder substance to personal hazard, and general annoyance for everyone around. Who wants to ice skate to their raised beds? Not me. Solid footing is scarce post-snow. Layers of ice and mud correlate with the cyclical freeze thaw cycle as we often see here in Western North Carolina. Dangerous ice and snow buildup on the road is a detriment to travel, and could potentially delay the delivery of seed catalogues, soil amendments, and plant propagation supplies.
Since ice presents a hazard to most mobile bodies, many to turn to a solution which is literally a “solution.” (stuff mixed up and dissolved in other stuff is called a “solution” in chemistry-speak). De-icing agents work by dissolving in water, increasing the number of dissolved ions, creating a "solution" (or mixture) and thereby reducing the purity of the water. Water that is less pure has a lower freezing point (stays liquid at colder temperatures). This is because the dissolved ions get in the way of forming the structural bonds between water molecules, preventing the formation of a crystalline structure of ice. The more ions dissolved in a liquid, the harder it is for it to get itself together and organized enough to form ice. There is a vague life lesson in here about decluttering... thanks ice for the weak analogy.
If your garden is near a road, driveway, or walking pathway were de-icing agents are used, it’s important to consider what kind of de-icer is applied, how much and how it might affect your plants, the soil and downstream waterways. There are many choices of salts to use to melt ice. Most of these choices have environmental drawbacks, especially when over-applied. So always use recommended application rates and you probably need to apply less than you think you do.
Rock Salt, (Sodium Chloride) is a popular, inexpensive choice that is definitely damaging and corrosive to metal surfaces, builds up in the soil and harms vegetation, and is harmful to both aquatic and terrestrial life in high concentrations. Other de-icing compounds such as Ammonium sulfate and Urea may actually fertilize your garden, but also results in excess runoff of dissolved nitrogen, harming water-based ecosystems. Calcium Magnesium Acetate (CMA) de-icer is formulated from dolomitic lime and acetic acid. CMA de-icer is a low corrosion and more environmentally friendly alternative to rock salt, but is not as effective below 15 degrees Fahrenheit. There are carbohydrate-based de-icers, made from corn syrup, molasses and beet juice. These are more garden and eco-friendly alternatives, however they are also often more expensive. The sugars from carbohydrate-based de-icers can have the effect of supercharging the activity of micro-organisms in the soil, which can have its benefits and drawbacks again depending on application rate.
Thanks for following along with us on this snowy sojourn. Hopefully this post has helped you find greater understanding, appreciation, and respect for this magnificent and powerful force of nature. How is snow affecting you in your garden/landscape and in your daily life? What are some joys and challenges you have faced gardening in winter? Please leave your comments below to continue the conversation!