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Hardening brassicas #865469
Asked April 22, 2024, 4:12 PM EDT
I have been hardening off my brassica plants for the past week or so. However, the nights have still been dipping into the 30's so I have not left them out overnight. Do they need to have an overnight before planting? If so how cold would the seedlings be able to tolerate?
Allegan County Michigan
Expert Response
Hi, thanks for the question.
Most brassicas can handle 28°F and lower for short periods. At 28°F you are looking at a 50/50 chance of it going lower on April 28. A lot depends on how much risk you wish to take. Seedling can be tender but should still hold up to a short period below freezing; however, it probably is not necessary in the hardening off process at this point. Some suggest transplanting once daytime temperatures are consistently above 40°. Soil temperatures (at two-inch depth) over 50°F is also a good target. Check out the following links:
When to Plant Vegetables in Allegan, MI - Garden.org
Frost Dates: First and last frost dates for Allegan, MI - Garden.org
Hardening off vegetable transplants is easy! - Gardening in Michigan (msu.edu)
I hope this is helpful.
