I am wondering your advice regarding when I should be hardening off my plants. Ideally I’d like to be hardening them off now to prep to get them into the ground but it’s been so cold outside I’m worried I may damage them. They are growing well so I don’t want to risk anything. I have tomatoes, basil, peppers, lavender, garlic, and onion. Thank you!
Hardening or “hardening off” is the process of slowly transitioning plants from a protected indoor environment to outdoor conditions of fluctuating temperatures, and exposure to sun and wind. This gradual introduction to the elements allows plants to build up root structures, accumulate carbohydrates, reduce water in the plant, and to thicken cell walls.
For most plants, this process should take place over about ten days to two weeks. Initially, plants should be placed in a shaded and protected area for two or three hours. Over the hardening period gradually increase the time the plants are exposed to the sun and wind. Cold frames are an excellent location for hardening off young plants, but any protected area (such as a porch) will work. You can check out how to effectively use cold frames in this Toronto Master Gardeners Gardening Guide.
Timing of the hardening process depends on the plant and your location. Check the seed pack instructions to see what temperatures your specific plants can tolerate, and then check weather conditions for your area to figure out an appropriate timetable. Garlic and onion tend to be hardier and can withstand colder initial temperatures, but tomatoes, basil and peppers are more tender, and temperatures should be at least 10°C consistently before beginning the process. Pay attention to the weather and avoid putting your plants out on very windy days, or days in which the temperature will dip below what your plants can safely tolerate.