Cold hardy and resilient, kale and collards are the most productive plants you can grow in your autumn garden. Plants set out now will produce an abundant crop of autumn greens, stand through winter with modest protection, and then explode with new growth in early spring. Both the leaves and buds from overwintered kale and collards are remarkably sweet and tender, and plants that are allowed to bloom become beacons for early season pollinators.
Collards and kale are both classified as Brassica oleracea, and have impressive nutritional profiles that include vitamins A, B, E and K. Established plants are winter hardy to at least 10°F (-12°C) without protection. Horticultural fleece and/or plastic covers further enhance winter survival of the plants.
Dark-leaved curly kale varieties like 'Redbor' make a beautiful statement in the winter garden, and provide vivid contrast with green-leaved varieties like ‘Prism’. ‘Red Russian’ kale has many devoted fans because it produces a heavy crop in autumn and then again in spring, followed by delectable flower buds. I especially like ‘Red Russian’ kale for overwintering because the leaves stay tender through all types of weather.
Among collard varieties, ‘Champion’ is easy and dependable, or you might try pale green ‘Yellow Cabbage’ collards, which are remarkably mild and tender. Be forewarned that collards are phenomenally productive plants that need picking twice a week in late autumn. Like kale, the plants slow down and rest when winter days are short and cold.
Growing Kale and Collards
Kale and collards are fast and easy to start from seed, or you can set out purchased seedlings. Do start with vigorous young plants rather than attempting to revive weary plants from spring. Unseen issues in the main stems of elderly plants spell doom when they are subjected to freezing winter weather.
You won’t need many plants, because four to six seedlings of each will astound you with their productivity. You will need a fertile planting site, because kale in particular needs rich, moist soil. I use the middle of an expired double row of sweet corn when possible, where the greens utilize soil nitrogen left from the corn. However, any open spot that can be outfitted with winter protection will do.
Constant soil moisture is needed to support fast growth, so make sure you can easily reach the plants with water.
Hot weather transplanting also must be done with care. Thoroughly water planting holes before setting out the plants, and then provide temporary shade for a few days. Several cabbage family pests can make quick work of gobbling down tender brassica seedlings, so play it safe by covering plants with horticultural fleece as soon as the seedlings are set out. I use shade covers to reduce heat stress to the little seedlings.
Protecting Plants Through Winter
When growing kale and collards through winter in areas with heavy snow, you will need a wire arch or other study support for holding up fleece or plastic. Things get ugly when a support structure fails and the plants get smashed by accumulated ice or snow, but there is an alternative. I have found that surrounding plants with 4 foot tall (1.2m) “wind fence” made of row cover attached to stakes protects the plants from wind and deer, the main winter hazards in my garden. Kale and collards know what to do with snow, and in fact seem a bit tickled by it.
Kale and collards are robust biennials, so plants that are vernalised by winter’s chill forge ahead with reproduction first thing in spring. The new flower buds are framed by a flush of tender young leaves, so you can pull and trim an entire plant for the kitchen. Unharvested buds give rise to spikes of yellow flowers that are of great interest to early-season pollinators. If you like, you can pick the peppery green seed pods, or let them mature to brown for seed saving - your final reward for growing kale and collards through winter.