Monroe County Master Gardener Association

Article written by Chris Eddolls

What lovely weather we are having in Michigan; it has been snowing for eight hours so far today, April 17, 2020! Four inches of heavy wet slush is lying all over the garden. It got me to thinking; what seeds can germinate in cool soil?

Here are some of the interesting facts on the subject I gleaned from the MSU Extension website and Smart Gardening tip sheet: Different vegetables, herbs and flowers have different germination requirements. That is important to know to ensure your gardening efforts are successful. Viable seeds are alive; they contain an embryo & stored food surrounded by a seed coat. Germination of viable seeds is dependent on a number of variables. All seeds germinate when the soil moisture, temperature, and oxygen levels are correct for that specific seed. Some seeds have unique light condition requirements that can add another variable in the process to successful germination. The majority of popular plant seeds require “normal” germination temperatures; that being the top few inches of soil having an optimal germination temperature of 65 deg. F to 85 deg. F; if soil is sufficiently moist and aerated. Moist means meeting a level of 50-70% of soil’s moisture-holding capacity; not wet soil.

Not surprisingly, most “cool-weather crops” can germinate at a soil temperature of 40 deg. F – 60 deg. F if the moisture and oxygen levels are optimum. For example, parsley seeds could be planted and will germinate when the soil is 40 degrees but a greater majority of seeds will germinate at the ‘optimum’ temperature range for parsley seed germination of 50 deg. F to 75 deg. F. This means at 40 deg. F, if the soil is wet instead of moist the seeds may rot, or if to dry or compacted the seeds may do nothing until the soil temperature moves closer to 75 deg. F then to 40 deg. F. Sometimes being the first to get seeds into the soil does not necessarily result in you being the first to harvest!

Cool soil germinators include many of our salad bowl favorites and perform nicely in patio pots as well as garden plots: Arugula, collards, kale, kohlrabi, leeks, lettuce, mustard, onions, parsley, radicchio, radish, and spinach. Be aware that many of these small seeds may actually ‘require’ light to germinate, therefore needing little to no soil cover. Not surprisingly, those cool loving crucifers can also germinate at cooler soil temperatures: broccoli, brussels sprouts, cabbage, cauliflower, Chinese cabbage. Don’t forget legumes, root crops and herbs which can all get a jump on the gardening season by germinating in cooler soil: beets, borage, carrots, chamomile, chervil, coriander, dill, marjoram, parsnip, peas and turnips.
Put on your long johns, get out into that garden and try some cool soil germinating crops!