Step 3 - Seed Starting
Fall Seed Starting
The second sowing season, counted back from first frost instead of last. It is the half of the year most first gardens never use.
Janet H. - the hands-on owner behind Janet Media Group.
Published - last updated
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Count back from your average first frost date by the crop's days to maturity, then add about two weeks because growth slows as days shorten. For most northern gardens that puts the main fall sowing in mid to late summer, which feels wrong and is correct.
What to sow for autumn and winter
| Crop | Sow | Notes |
|---|---|---|
| Spinach | 8 to 10 weeks before first frost | Very hardy; will often overwinter under a cover |
| Kale | 10 to 12 weeks before | Flavor genuinely improves after frost |
| Lettuce (hardy types) | 8 to 10 weeks before | Germinates poorly in hot soil -- start in a shaded tray |
| Radishes | 4 to 6 weeks before | Fast; can be sown in succession right up to frost |
| Turnips | 8 to 10 weeks before | Roots and greens both useful |
| Mache and winter salads | 8 weeks before | The hardiest salad there is; survives hard frost |
| Garlic | Plant cloves 4 to 6 weeks before ground freezes | Harvested the following summer |
Why late-summer sowing is different
Spring sowing fights cold soil. Late-summer sowing fights heat and drying. Soil in August germinates seed fast, but a tray or a seed row can dry out in a single afternoon, and lettuce in particular germinates poorly when soil is warm.
The workarounds are simple: sow into a tray kept in shade rather than direct into hot soil, water more often than feels necessary, and shade the seed row with a board or a piece of shade cloth until seedlings emerge.
Frost improves some crops
Kale, cabbage, Brussels sprouts, parsnips and leeks all sweeten after a frost -- the plant converts starch to sugar as a form of antifreeze. A parsnip lifted before any cold weather is noticeably less sweet than the same root after two frosts.
That is a genuine reason to plan a fall crop rather than treating the season as an afterthought.
Extending into winter
A cold frame over part of a bed carries hardy greens weeks or months further than the open garden, and it costs very little. An unheated greenhouse does more of the same on a larger scale.
Neither produces summer crops in winter. What they do is keep hardy things alive and pickable when the open bed has stopped -- which is a modest, reliable and genuinely useful outcome.
For the spring half of the calendar, see when to start seeds indoors.
What to buy
The products that fit the advice above, chosen by the process on our how we choose page. We have not hands-on tested them; specifications are the manufacturers’ own.
Quick picks
| # | Product | Best for | Score | Price |
|---|---|---|---|---|
| 1 |  Top pickEspoma Organic Seed Starter MixFine, low-nutrient starting medium | Most seed trays | 8.9 | Check price on Amazon |
| 2 |  VIVOSUN Cold Frame Mini GreenhouseLow-profile frame with hinged clear lid | Extending the season over a bed | 8.0 | Check price on Amazon |
| 3 |  Burpee Self-Watering Seed Starting KitCell tray, dome and watering mat in one box | First-time seed starting | 8.4 | Check price on Amazon |
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Scores are our own editorial judgment, formed from published specifications and independent sources. They are not aggregated customer ratings, and they are not the result of hands-on testing, which we do not currently do. See how we choose.
Common questions
When should I start seeds for a fall garden?
Count back from your average first frost date by the crop's days to maturity, then add about two weeks because shortening days slow growth. In most northern gardens that puts the main fall sowing in mid to late summer, which feels early but is right.
What vegetables can I plant in late summer?
Spinach, kale, hardy lettuces, radishes, turnips, mache and other winter salads. Garlic goes in later, four to six weeks before the ground freezes, for harvest the following summer. All of these tolerate cold and several improve after frost.
Why won't my lettuce germinate in late summer?
Lettuce germination is inhibited by warm soil. Sow into a tray kept somewhere shaded and cool rather than directly into hot ground, keep the medium damp, and transplant once seedlings are up. Shading a direct-sown row with a board also works.
Do vegetables really taste better after frost?
Several do. Kale, cabbage, Brussels sprouts, parsnips and leeks convert starch to sugar in response to cold, as a form of antifreeze. The difference in a parsnip lifted after two frosts compared with one lifted in warm weather is easy to taste.
Sources
Factual claims on this page are backed by the published sources below, and product specifications are the manufacturers’ own. Where a figure is not published, we say so rather than estimating it.