Using Snow to Water Gardens, Insulate Plants, and Change Your Growing Zone
As a gardener, winter presents an ideal opportunity to harvest, move, pile, and store water for the upcoming gardening season. It’s time to talk about snow farming.
Snow farming goes beyond storing water. Strategically placed snow can reduce winter damage, increase the survival rate of herbaceous perennials and woody plants, boost fruit production, minimize freeze-thaw cycles, and even expand your growing zone.
Thinking Outside the Barrel
When most people think about water harvesting, their minds go straight to rain barrels. And don’t get me wrong—rain barrels are an excellent, if not slightly bulky, often over-engineered water-harvesting technology. They help capture rain for later use, but as a water-harvesting method, barrels didn’t even make my list of the top five ways to keep your garden watered—full confession: While I intend to, after 10 years, I still haven’t installed rain barrels at my home.
A significant flaw of rain barrels is that they don’t work when temperatures dip below freezing. Barrels and hoses filled with water tend to freeze and burst in the fall.
A significant flaw in our thinking is believing that the gardening season is over once crops are in, perennial plants are dormant, and taps can’t flow. All water-harvesting activities seem to stop. This is a missed opportunity.
Snow farming is the strategic collection, movement, and placement of snow to harvest water, insulate plants, and create microclimates.
Winter Water Harvesting
Unlike its warmer self, snow can be pushed, shovelled, tossed, and piled precisely where needed. With some planning and forethought, yards, gardens, or even entire cities could be designed to take advantage of water in its most insulative and storable form. We view snow as an inconvenience worth removing, but it’s a precious resource we should strategically store in the landscape.
The Benefits of Snow Farming
Let’s assume you use clean snow free of contaminants like salts and deicers. We used to salt the earth of our enemies, and now we willingly do it to ourselves because – convenience? Salt will wreck your shoes, rust your car, and kill your plants. In the best case, it gets flushed down the drain, wasting water and polluting ecosystems. Stop. If it’s unsafe to throw on your garden, it’s unsafe to throw on your sidewalk.
A second point I’ll make is that if you’re designing a garden, consider placing perennial beds and tender plants near where you’ll be shovelling. Good design will prevent you from having to move snow across your yard—shovel as usual and pile the snow onto your adjacent plants and garden beds.
Snow Waters Your Garden
The obvious benefit of snow farming is that snow is water, so shovelling snow into garden beds and around trees puts water exactly where it will be needed when it melts in spring. However, increased moisture is only one benefit of snow farming.
Snow Insulates the Ground and Protect Plants
I live in Edmonton, Alberta, where it’s not uncommon to receive winter temperatures below -30°C, and yet, studies suggest that the ground temperature is typically between -3°C and -5°C. How is this possible?
Counterintuitively, snow is an excellent insulator. Freshly fallen snow can be more than 90% air. A blanket of snow helps trap heat in the ground by providing a thermal break between the warmer earth and the colder atmosphere.
By intentionally adding snow around trees and perennials, gardeners can insulate the roots of plants (roots are often half of the plant). Protecting roots from extreme temperatures will increase the survival rate of many plants.
For this strategy to work, the snow must remain relatively undisturbed. Walking on or compacting the snow removes the air and reduces the insulative effect.
Snow Prolongs Winter Dormancy & Increases Fruit Production
Snow keeps the ground warm throughout winter but has the opposite effect in the spring as daytime temperatures rise. Blanked in snow, the ground and plants’ roots contained within remain colder for longer – keeping plants dormant longer. Why is this helpful? Because delaying growth in the spring can protect newly developing leaf and flower buds from late frosts.
Snow farming benefits fruiting trees and shrubs as late frosts freeze and kill flower blossoms and any chance of fruit for the season. Prunus, the plant genus containing cherries, plums, peaches, and apricots, are early bloomers and famously susceptible to late frosts. Increasing snow depth around these trees delays flowering for a few weeks, increasing the likelihood of a harvest.
Snow Reduces Freeze-Thaw Cycles
Any gardener will tell you that freeze-thaw cycles are tough on plants. A freeze-thaw cycle is when temperatures rise above and below freezing (0°C). Like all living things, plants are mostly water, so the continuous freezing and thawing of cells (and the water within) can be damaging.
This next section gets a little wonkish, so here’s the tldr (too long, didn’t read) version:
- It takes a lot of energy to freeze or thaw water.
- Melting cools your garden.
- Freezing warms your garden.
- The more water in your garden, the fewer freeze and thaw cycles.
Counterintuitively, storing more water in the landscape tempers freeze-thaw cycles by absorbing and releasing heat without changing temperature.
A quirk of phase transitions (water to ice or ice to water, for example) is that energy changes the state but not the temperature. So, when water is freezing or melting, it maintains a constant temperature of exactly 0°C. The effect is that the more water in your landscape, the more difficult it is to push the landscape above or below freezing.
An added quirk of this process is that freezing releases heat, and melting absorbs heat. A melting pile of snow absorbs heat, actively cooling its surroundings and slowing its own melting. The reverse is also true: a freezing puddle of water is actively warming its surroundings and slowing its freezing 🤯.
The effect is that adding snow to your garden and perennial beds will reduce temperature swings – especially swings above and below freezing.
Snow Farming Can Create Microclimates
According to Natural Resouces Canada, the growing zones are influenced by seven factors. By adding snow to our yards, piling snow around plants, and increasing the water-holding capacity of our gardens, we can indirectly influence four and directly influence one of these seven variables:
- Directly increase the average minimum temperature in the coldest month by protecting plants below the snow. This is ideal for shrubs and tender herbaceous perennials. (1.734)
- Reducing freeze-thaw cycles can increase the average number of frost-free days above 0°C. (0.186)
- The amount of rainfall from June to November (69.770)
- The average maximum temperature in the warmest month (1.256)
- A winter factor that includes January rainfall (0.006)
- Directly increase the average maximum snow depth (22.370)
- Lower the maximum wind gust in 30 years by protecting plants below the snow. (- 0.018)
The number at the end of each variable is a coefficient that indicates how impactful each variable is on plant hardiness. For comparison, average minimum temperatures in the coldest months has a coefficient of 1.734, and the average snow depth has a coefficient of 22.370—suggesting that the average snow depth is ~13 times more impactful on a location’s hardiness zone than temperature.
Visit the Natural Resources Canada website for the complete Canadian Hardiness Index formula or to look up your Canadian municipality’s hardiness zone.
Beyond The Backyard. Snow Farming at the City Scale and Snow as an Asset
Unfortunately, cities have an awkward relationship with water, and the white fluffy stuff is no exception. Cities see snow as an impediment and spend millions of dollars yearly pushing, scooping, and hauling snow off the landscape.
In the face of a changing and often drying climate, it’s worth asking what a city that thought of snow as an asset might look like. What if we were all snow farmers?
