Plants that are not afraid of the cold

The agricultural season is short in Quebec. Betting on plants that have proven themselves in the rigors of our climate is a winning strategy for maximizing the chances of success in the garden and vegetable patch. Update on hardiness factors.

Isabelle Morin
The Press

hardiness zones

Some varieties and cultivars, prolific where the summers are longer, struggle to evolve in the short window of heat allocated to them in Quebec. These specimens may be able to grow and even produce some fruit under our conditions, without however giving their full yield or being resistant to diseases and invaders. This is why hardiness is an essential factor when selecting plants. It guarantees that they will have the capacity to marry the conditions offered to them. They will therefore require less care to achieve similar or better results than other less well-adapted plants.

The numbers associated with Quebec hardiness zones range between 0 and 5b. They are a reference for categorizing the territory according to the minimum temperatures reached in winter. The lower the number, the colder the winter in a given territory. If you live in a 4b zone, for example, the choice of plants that can adapt to this zone and other cooler ones (1a, 1b, 2a, 2b, 3a, 3c, 4a, 4b) is recommended, the letter “b” indicating a zone warmer than “a”. Certain growing conditions can cause these data to fluctuate slightly: altitude, the amount of sunshine on the ground, whether or not the plant is protected from the wind, whether it grows in the ground or in a pot, etc.

If in doubt, you can improve your chances of success by giving the plant warmer conditions than normal in the area. But since the label that accompanies commercial plants displays the minimum hardiness zone tolerated by the plant, sticking to a selection adapted to its hardiness zone is generally a guarantee of success.

The hardiness of annuals

Hardiness zones are mainly used as a reference to classify trees, shrubs and perennials that spend the winter in the garden. Annuals, which only live for one season in our conditions, also have “hardiness”, a term we refer to to describe their ability to tolerate a more or less cool climate.

“When we choose seeds, we mainly refer to the number of days before going to maturity from the seedling, or transplant, to the harvest,” says seed company Catherine June Wallenberg, of Northern Seeds. The plant will have to benefit from this number of days to complete its cycle before the temperatures are no longer favorable to it, which varies according to the hardiness zones.

Tender annuals

These must be sown indoors a few weeks before planting in the garden, and more or less early depending on the plant family. In the vegetable garden, the category includes, among other things, tomatoes, eggplants, cucumbers and basil, and on the flower side, coleus, nicotine or marigold. Tender annuals should be sown or transplanted to the garden when the temperature does not drop below 10°C.

Semi-hardy annuals

Endives, Chinese cabbage, lettuce, potatoes, nasturtiums, petunias, coneflowers and others adapt to cool temperatures without tolerating frost. We can save time for harvesting by starting their sowing in the heat, with the exception of potatoes, which are started directly in the garden. Before transplanting or sowing them in the vegetable garden, however, you will have to wait until all risk of frost on the ground has passed.

Hardy annuals

Cabbages, carrots, spinach, turnips, radishes, peas, broccoli, sunflowers, poppies and marigolds, all less chilly, can be sown or planted even before the last frosts, as soon as the soil can be worked, in other words, as soon as it is drained of its excess water or about three to four weeks after the snow melts.

A variable nervousness

Hardiness varies within the same plant family and species. Take the example of the tomato. Like all plants of the nightshade family, which includes peppers, eggplants or petunias, it must be sown indoors several weeks before planting to have a chance to develop its fruits before the cold weather returns.

However, its hardiness also differs according to its botanical variety or cultivar (cultivated variety). A “northern” selection such as the “Black Prince”, which is an ancestral tomato from Siberia, is able to offer beautiful fruit even in a cool climate, explains Catherine June Wallenberg who, like a majority of Quebec seed producers, s strives to develop and preserve plants that are successful in our conditions.

“Just the fact of growing and harvesting certain plants generation after generation in an environment like ours generates selection. If I have a frost on my farm on June 3, as I often do, I can lose 40% of my squash plants, but I know that the remaining 60% will have some tolerance to our bioregion”, she gives as an example.

Seeds hardy in Quebec offer some resistance to cold and will mature more quickly in a short season. They will be able to germinate in low temperatures and will resist some known diseases in our cool, humid conditions. “Plants adapted to northern conditions will often have a smaller fruit in common,” she notes. A tomato the size of a plum or a peach is more likely to mature quickly than one weighing 2 lbs, and the same goes for a watermelon. Here in Quebec, we don’t make big 20 lb melons! »

If a lettuce goes without problem to maturity in Quebec without it being necessary to be interested in its cultivar or its variety, it is different for the plants more sensitive to the cold, specifies Catherine June Wallenberg. “In the case of a tomato, it’s really to your advantage to choose one that has proven itself in a northern climate. This maximizes the chances of obtaining good fruit, in good quantity. »