Part 3. Focus on Crops for Overwintering
Overwintered Crops are planted in fall or winter, and left in place through the winter to provide for the earliest possible spring harvest. One approach to planting is to time seeding so germination and the first stages of growth occur before day length decreases to less than 10 hours — at this point, plants will go dormant. Growth will resume as daylight increases. Another approach is to time seeding so germination takes place after daylight has increased to 10 hours or more.
Keep in mind that widely fluctuating spring weather patterns can trigger premature bolting, and prolonged wet conditions cause a higher occurrence of seed rot. We recommend that you test timing in your location before making large plantings.
Here are some further recommendations from Johnny's Research Team, for crops that can be seeded in fall or winter for harvest the following spring.
Start with spinach varieties selected for overwintering.
Seed several times for the longest harvest in spring. Schedule the first seeding so that the cotyledons or first true leaves emerge in fall but then go dormant in winter. Sow again in winter so the seeds will germinate as the days get warmer and longer. In warm winters, spinach may germinate and be harvestable in winter.
Plant late fall to early winter or as late as the soil can be worked. Mulching with row cover or straw will help prevent the soil from freezing before the desired sowing date. To ensure sweet roots, harvest promptly in spring before temperatures get too high in mid spring. Row cover can help warm the soil to a certain extent and help protect roots from freezing, which allows for earlier harvesting.
The best overwintering onion is Bridger, which can be direct-sown or transplanted in fall.
For extra-early onions, sell bunched bulbs before they have matured and the tops have fallen over. After the tops have fallen over, remove them and sell by the pound.
The success of overwintered onions varies based on region and weather, as multiple rapid temperature fluctuations can kill a crop. Later plantings in the fall will have less tendency to bolt, but the ready-for-market date of the bulbs will also be later. Remember to test timing in your location before making large plantings.
Parsnips require 120 days to reach maturity, so they are generally planted in mid to late spring and harvested in fall for storage. However, you can leave some in the ground to overwinter, to supply your early spring markets with extra-sweet roots.
Overwintered parsnips must be harvested before the tops begin to grow. After harvesting, be very gentle with the roots as they will bruise much more easily than carrots. Plant in deeply worked soil for attractive, well developed roots.
These are the crops and varieties determined by Johnny's Research Team to perform favorably when overwintered for early spring harvest. Refer to the following resources to learn more about key methods and crops for producing fresh offerings throughout the winter into early spring.
- Part 1. Get Set for Winter Growing: Definitions, Methods, & Scheduling »
- Part 2. Focus on Crops for Winter Harvest »
- 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).