Here in our Canadian climate, the free-thaw cycle can create a number of challenges in our gardens. In this week’s tip, we’ll discuss what it is, and how you can minimize the chance of your plants getting damaged from this seasonal phenomenon.

As fall turns to winter and winter turns to spring, the ground can shift and change as the soil freezes and then thaws. This happens when warm, sunny days are followed by frosty nights. We know from science that water expands when it freezes. Because water distribution in soil isn’t always perfectly distributed, the amount of expansion and contraction changes. Drier soil doesn’t shift as much, while wetter soils will be more prone to the process.

One of the most common issues people will face will be with their container gardens. If your container isn’t properly winterized, it can crack, break, or become more brittle with each of the freeze thaw cycles it endures. It is important to choose containers that are frost proof, or to empty your containers of some or all of their soil before storing them for the winter. Another tip is if you let your containers freeze over the winter, keep them frozen a bit longer to minimize the risk of having them re-freeze on a cold night in the spring.

A second common issue will be lifting plants and bulbs out of the soil. When the soil freezes and expands, it can rip roots and bulbs up and out of their original spot. When the ground thaws, it collapses leaving exposed roots that will be subject to drying wind and hungry animals. If you see any plants/bulbs lifted out of the soil, gently push them back into the ground using the existing soil or adding in extra compost/mulch. A good way to minimize this from happening is to use snow as an insulating blanket and to minimize the temperature fluctuations happening right at the soil level.

A final and often unexpected casualty of the free-thaw cycle could be sunscald on your fruit trees. Especially on the south side of the trunk, the bark can increase in temperature on a bright and sunny day, causing growth and water to move into the surrounding tissues. A subsequent drop in temperature can then freeze the water, split the bark, and damage the tree. To minimize this damage, avoid heavy pruning in the fall that can open up too much of the canopy. Another common preventative measure you can take is to paint the bark of the tree with a diluted white latex paint (one gallon of paint to 4-5 quarts of water). This can have an added benefit of preventing boring insects from attacking the tree.

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