Scheduling Guidelines for OVERWINTERED CROPS

Welcoming the end of the Persephone Period

Here in mid Maine, the Persephone period ends on February 6, when daylight at our latitude again reaches 10 hours in length.

Overwintering entails establishing very young plants that can survive the winter and resume growth extra early the following spring. Once daylength increases to 10 hours, these plantings will grow rapidly.

Keep in mind that wide fluctuations in late-winter temperatures can sometimes cause overwintered crops to bolt before they reach a harvestable stage. This can be minimized by choosing varieties with greater bolting tolerance. (See our Good for Overwintering category, for which varieties are selected on this basis through our overwinter trialing programs.)

The most calculated approach to scheduling seeding for overwintered crops involves seeding in the late summer to late fall, depending upon the crop. (Be sure to review the Overwinter Planting Chart for the crop-specific planting windows.) The correct timing will allow germination and the first stages of growth to occur before the plant goes dormant during the Persephone period. Growth will begin again when days begin to lengthen.

Another overwintering method involves sowing just before the ground freezes, so that germination occurs after deep winter, as daylength increases and temperatures warm. This method can result in a lot of dead seed, however, if conditions do not pan out. (There is a risk that a higher percentage of seeds will rot in the soil during cold, wet conditions.)

An additional strategy is to seed just as the ground begins to thaw, or just as the Persephone period is ending (so technically, this is not overwintering). This works well for direct-seeded spinach and brassicas. Only the top inch or two of soil needs to be thawed in order to plant the seed.

The Persephone Period: 10 hours of daylight

Use our clickable Overwinter Planting Chart as a guide, staggering your vegetable plantings by the week for successive earliest-spring harvests.

View Chart…

Use our clickable Overwinter Planting Chart to time your planting dates for earliest spring vegetable harvest.

Keep in mind that the planting dates are back-scheduled from the last 10-hour day at your latitude.

The number of weeks before the Persephone period is calculated for each listed crop.

The vegetable crops are grouped, as outlined in the chart key, to reflect their reliability for overwintering success.

We offer two dozen videos on Overwinter Flower Production!

View all our educational resources on overwinter flower production…

How to extend your growing season with cold-hardy annuals

After several years of research and trialing, we are pleased to share the results of our overwinter flower trials. Along with the Winter Growing Guide information here in Johnny's Grower's Library—which pertains primarily to vegetable crops—we now offer an extensive series of educational resources on overwintering flowers:

• Guide to Overwintering Flowers
• Results by crop
• Calculator to determine seeding dates
• Video tutorials & webinar resources