Question: I usually start seeds indoors in the winter or sow them in the spring, but I've heard you can sometimes sow them outdoors in the fall and they'll sprout in the spring. This would be easier since I don't have as much free time in the spring. What can you tell me about fall seed sowing?
Answer: Many types of seeds will survive the winter in the ground and sprout in the spring. After all, this is how it often works in nature; a wild plant sheds its seed in autumn and the seedling comes up in spring. That's why many perennial-seed packets will instruct you to "cold stratify" the seed before sowing it by storing it for several months in your refrigerator. This just recreates the winter conditions and the thawing that triggers the seed to sprout in nature.
To plant seeds outdoors in fall, follow the same steps you would take in the spring. Clear the area of weeds, grass, etc. Try not to till the earth much (read why not to till). In cold-winter areas, wait until after a killing frost to sow the seeds, or at least until you're sure the growing season has ended. (Often you can just sow the seeds at the same time you plant bulbs.) In warm-winter areas, sow the seeds just before the rainy season begins, or from late fall into winter. Most likely seedlings won't appear until the spring, but if you do see them and you're in a cold area, mulch over them once the ground has frozen completely.
Annuals that can be sown in the fall are generally those that are known for spreading on their own by self-sowing, such as annual poppies, larkspur, love-in-a-mist and pansies. So-called "hardy annuals" also work. Biennials to sow in the fall are foxgloves, sweet William and hollyhocks, among others. For perennials, consider how/if/when the plant self-sows. Coneflowers, hardy geraniums, columbines, black-eyed Susans and others drop their seed in autumn. These are good candidates for fall sowing, as are any whose seed packets indicate the need for cold stratification.
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