It has been an exceptionally snowy winter this year for much of Europe and America and this can have a big impact in the garden. Many late crops are still over-wintering and, whilst the snow can transform your vegetable patch into a beautiful winter scene, it can also cause problems for plants. So, what are the options for protecting crops from damage due to wintry weather?
Snow is actually quite good for a garden in many ways, or at least it is the best of the freezing weather options. Because of the ‘fluffy’ structure of snowflakes a lot of air is trapped and this acts as a very effective insulator. So, while the temperatures are not going to be high under a blanket of snow, the plants below are protected from air temperatures which may plummet well below freezing.
Many winter plants can happily survive freezing temperatures. The main problems are due to related factors:
- Wind-chill: If a plant is exposed to icy-cold winds then the effective temperature can drop much lower than the predicted air temperature. It is not uncommon for a reasonable breeze (30 km/h or 20mph) to turn slightly freezing conditions (say 0°C, 32°F) into something far more destructive for plants (-7°C, 19°F). The lower the temperature of the air, the greater the influence of wind-chill and associated temperature drop. So, sheltering plants from winds should be a priority in cold weather.
- Loss of water: Again, often caused by wind, plants can become dehydrated as moisture is lifted from their leaves. If the plant is shallow-rooted then frozen ground can also prevent the uptake of water from the soil. So, if dry cold winds are predicted then protection should be arranged. It can also be worthwhile watering the roots a little and then mulching to maintain a source of moisture for the plant without locking it up as ice.
- Sudden changes in temperature: It is tempting to quickly shift snow away from plants as soon as the sun shines but this can, in fact, be damaging. Frozen plants need to slowly thaw out and a sudden change from freezing temperatures to warm sun can damage the plant’s cell tissue.
- Crushing: Too much snow, snow blown about in drifts or sudden drops of snow from a roof or tree can crush plants. If your plants are in danger of a sudden deluge of snow then it may be worth shaking or clearing it off the higher structure to avoid it suddenly falling. In Switzerland conifer branches are laid amongst leeks to hold up the snow and this technique can be extended to other vulnerable plants.
- Hungry Wildlife: Snow removes many of the food sources for birds and animals so crops can be particularly vulnerable. Pigeons and other larger birds will love to eat brassicas and any remaining root crops that can be dug up will be sought out by rabbits. The best solution is usually to net the crops making sure that all gaps are closed and firmly anchored down. (However, in my experience rabbits will burrow under almost any barrier!)
For many crops the addition of cloches or row-covers will be a useful precaution against much of the above. If the weather turns suddenly sunny then the ends of the cover will need to be opened during the day to allow sufficient ventilation and prevent too-rapid thawing. Mulches will also be useful and larger plants can be wrapped in plastic sheet or sacking. For smaller plants, laying several sheets of newspaper on top weighed down with bricks will offer some protection.
Vegetables that Benefit from Frost
Although all these precautions may seem lengthy and a lot of work, there are benefits to freezing temperatures. Rather than harvesting every crop before winter, some will benefit from a light frost as it helps their flavour to develop:
- Brassicas, such as Brussels sprouts, cabbage, broccoli, turnips, winter radish and kale will all develop a better flavor during cold weather. Some of these can even be harvested during the winter weather and it is recommended that you cook kale leaves directly from their frozen state.
- Parsnips (and some Carrots): Frost helps turn the starches in parsnips into sugars to give the characteristically sweet taste. However, harvesting parsnips from frozen ground is not an exercise I would recommend – you need to wait until the ground has completely thawed!
- Endive and Radicchio: Again, a light frost can improve the flavor of these slightly-bitter plants as can blanching them after harvest.
A Mixed Blessing
So, snow can be both beneficial and harmful. For most of the time snow is best left on the ground and not cleared off the vegetable patch. Avoid walking on snow-covered beds as this will just compact it to ice so that it ceases to insulate the plants. Assess each of the potential problems listed above and, if necessary, add covers, mulch, netting or other shelter. Finally, remember that plants are often more resilient than we think and a few weeks into spring they may suddenly produce new growth despite a tough winter.
If you have any tips on how to protect plants from snowy conditions, please do add them below...