COLUMBIA, S.C. — December is the second coldest month of the year on average in Columbia, SC. It’s a hostile time for warm loving plants, but the perfect time of year for hardy winter greens. In this article, we’ll look at the plants that are growing in our garden outside WLTX in December 2021 and what can grow (and thrive!) in South Carolina this time of the year.
One plant species is responsible for dozens of types of winter produce.
Summer garden favorites have, for the most part, frosted over, but fall plants like broccoli, collards, cabbage, and cauliflower are hitting their stride in Gandy's Garden at WLTX. These all have identical growing requirements because they’re the same plant species! Each are a different variety of “Brassica oleracea”, developed over thousands of years to accentuate specific parts of the plant for produce. Collards, cabbage, and kale are grown for their tasty leaves, while broccoli and cauliflower have delicious flower buds.
These are cool season plants and are best planted in late summer for a fall or winter crop, or in late winter for a spring crop. The summer heat in South Carolina is too intense for these to produce reliably, but the cooler season is perfect for them. The broccoli, cauliflower, collards, and cabbage were planted as starter seedlings in early September. The broccoli and cauliflower started producing their florets in late November, about 2 months later. You can expect to pick broccoli and Cauliflower about 3 months after planting seedlings, or 4 months if you’re starting them from seed.
Starting from seed
Some winter crops are so easy to grow that they’re worth starting from seed. Lettuce seeds are tiny, but quick to sprout. The lettuce outside WLTX were started from seed in early September in tiny pots and then transferred into our raised beds in October. Lettuce is so easy to start from seed, that we get some lettuce each fall from the previous winter’s crop. They can be picked all at once after a few weeks of growing as bundle, or the leaves can be pulled off periodically throughout the season to keep the plant alive and producing. Similar leafy greens like Arugula are just as easy to start from seed. These plants prefer cooler temperatures because warm weather will cause the plants to “bolt” which describes the plant when it begins to produce blooms. At this point, the leaves are no longer tasty.
Parsley has surprisingly been a winter perennial for us outside WLTX. The plants that we started in fall 2020 died after flowering during the summer, but sprouted from the roots when the weather cooled down this past fall. Meanwhile, volunteer parsley seedlings are sprouting in our raised beds, which is proof that this is another winter green that is easy to start from seed.
Planting in December
December isn’t an ideal time for planting, but we’ve had luck starting broccoli seeds outside in January 2020 for a May crop and this year we’re trying arugula from seed and planting onion bulbs. Arugula seeds are very small so these were started in a small tray of pots and will go inside on cold nights to encourage quick growth. Plants grow slowly this time of year even during mild days because there are so few hours of daylight, so it will likely take twice as long -- about 2 months, for the arugula to be old enough to transplant into the garden. The onions will sprout as the weather warms up. The bulbs that are planted close to the soil surface will swell and be "dinner ready" when consistently warm weather arrives. Bulbs planted deeper will have smaller roots, but produce more leaves, which is perfect for gardeners looking for "spring onions".
Weather plays a role in a garden's success.
Autumn is a transition growing season, the only thing that's consistent is how inconsistent the weather is. However, even by fall standards, autumn 2021 has been unusual across the country. According to NOAA, this past fall was the third warmest on record across the contiguous United States. However, the weather in the South Carolina Midlands this autumn was drier, and at times cooler, than normal.
Gardeners on our WLTX Gandy’s Garden Facebook group took notice, commenting that some autumn plants like collards were growing slower than usual. In Columbia, November was the 3rd driest on record, and there were 8 mornings reported at or below freezing. Overall, morning low temperatures in November 2021 were the 11th coldest on record. Records go back to 1888 in the city.
Despite the cold mornings, some gardeners in the Midlands went into December with pockets of the summer garden free of freeze damage. Temperatures dropped as low as 25F in Columbia, but that “official temperature” is only for record keeping. This number doesn’t represent specific microclimates in the home garden. On calm, clear nights, temperatures drop quickly by thermometers, which are placed in open fields 5 feet above the ground. When winds are light, warm pockets can persist in areas near buildings, under trees, or in higher parts of the garden where warmth doesn’t escape as easily. These warm pockets aren’t reliable though. As soon as breezy freeze arrives, some of these spots could be just as cold as an open field.
As we approach January, the coolest month of the year climatologically for Columbia, SC, deep arctic freezes can threaten even the cold tolerant plants in the garden. Most winter greens can survive temperatures below 25F without any damage, but will show damage around 20F, or with prolonged freezes. It’s worth protecting plants when night temperatures are expected to drop below 25F, although some plants like cabbage and kale can easily handle temperatures into the teens without damage.
Are you a gardener in the Midlands? Join the conversation on our Facebook Group, WLTX Gandy’s Garden!