Part 2. Focus on Crops for Winter Harvest
Winter Harvest Crops are planted in late summer or early fall for harvest throughout the winter. Here are some tips from Johnny's Research Team for growing crops that can be harvested all winter from a low tunnel or high tunnel. We also recommend that you test timing in your location before making large plantings.
Spinach is known as the "Winter Growing Money Maker" because consumer demand is reliably high through winter. It's great for all skill levels and makes a good crop for success if you are just starting out with winter growing.
Seed your winter-harvest spinach 40–50 days before day length drops to 10 hours. This includes about a week for germination. Multiple seedings will result in the longest overall harvest window during the later parts of the winter. Seed thickly to ensure a good stand, and plan on thinning. Spinach does not germinate well under warm conditions, which is often the case when seeding for winter. To help germination, irrigate before planting to cool the soil.
Winter spinach is exceptionally sweet because the plant builds up sugars to protect cells from bursting in freezing conditions. Sometimes this sugary liquid will form small droplets on the underside of spinach leaves. This is not an indication of anything wrong and, in fact, indicates that the flavor will be sweet.
Kale | Collards
Kale may be the trendiest vegetable in the United States right now. It is reliably cold hardy, and in fact its flavor improves in cold weather, as with most brassicas.
Collards are well known in the South because they can stand the heat without tasting offensively bitter, but they are equally cold tolerant and deserve to be planted alongside the winter kale crop.
Seed kale and collards in late July or early August for September transplanting. Harvest late October through March by clipping leaves from the bottom up. Both are suitable for low tunnels or high tunnels. Cover with lightweight row cover if flea beetles or cabbage loopers are a problem. Wildly fluctuating temperatures can result in cold damage to the leaves.
All varieties of kale can be grown in winter, but curled types are a bit hardier and make bigger bunches quickly (less time spent picking; bunches look fuller on the stand). All varieties of collards are acceptable. One marketing idea is to grow several varieties and sell them in mixed bunches.
Claytonia, Mâche, Minutina, and Sylvetta can be grown in an unheated hoophouse without a second layer of row cover because they are very cold hardy. They may not grow much when day length is less than 10 hours, but they can be harvested during that time.
Plant greens for winter harvest August through October for harvest September through March. Soil temperature when seeding should be 70°F/21.1°C or lower to avoid poor germination.
Sell mâche bagged, in clamshells, or as loose rosettes so customers can choose their desired quantity. Add claytonia or minutina to winter salad mixes.
Lettuce is less cold hardy than other greens, and should be grown in a heated greenhouse or under an inner tunnel inside an unheated hoophouse. Fluctuating temperatures in fall may result in uneven growth rates within a stand.
Direct-seed scallions in August and start harvesting when they have reached the desired size.
Scallions are easy to grow for winter harvesting, although some heat may be required if temperatures are very cold.
Cleaning scallions can be time-consuming; they require access to running water and a packing shed. Sell in bunches with other salad or sauté items.
Winter-harvested carrots are super sweet; Eliot Coleman markets his as Candy Carrots. Another attribute is that they are fresh, but not green like most other winter-harvest crops.
Carrots grown under protective covers typically have nicer tops. Bunched carrots with attractive tops indicate freshness and will help you sell them, but customers should be advised to remove tops before storing carrots to prolong freshness because the tops respire and will cause the roots to lose water. Some growers will remove the tops for the customer upon purchase. If the tops are not nice or are too hard to clean, they can be cut an inch or two above the shoulder to show that they are fresh carrots, not storage carrots.
Sow September through October for harvest October through December. Cover with lightweight row cover if flea beetles are a problem. Although radishes are quite cold-tolerant, they will go spongy if frozen hard repeatedly.
Other Winter Roots | Turnips & Beets
Direct-seed turnips and beets in fall, planting enough to allow for a long winter harvest period. Beets may do better in a warm hoophouse because growth rate drops off when it gets really cold. Use row cover on turnips if flea beetles are a problem.
From fresh harvest, you can sell beets and turnips bunched with tops if the tops look nice. If the tops have frost damage, or the turnips are coming from storage, they can be sold topped, loose, or bagged.
These are the crops and varieties determined by Johnny's Research Team to perform favorably when grown for winter harvest. Refer to the following resources to learn more about key methods and crops for producing fresh offerings all winter and into earliest spring.
- Part 1. Get Set for Winter Growing: Definitions, Methods, & Scheduling »
- Part 3. Focus on Crops for Overwintering »
- View a comprehensive list of Recommended Crops for Winter Harvest »
- View a comprehensive list of Recommended Crops for Overwintering »
- The Winter Harvest Handbook, by Eliot Coleman. See sections on The Cold Greenhouse (pp. 55–66) and Managing Quick Hoops (pp. 125–129).
- High Tunnels: Using Low-Cost Technology to Increase Yields, Improve Quality, and Extend the Season, by Tracy Frisch and Ted Blomgren. See sections on Interior Row Covers (p. 50) and Supporting Interior Tunnels (p. 54).