You can sow both perennial, and many annual flowers in the fall. Some perennials germinate best when stratified (exposed to a cold, moist period), which will naturally occur with fall sowing. Some annual flower seeds can survive a cold, moist winter, and germinate quickly in the spring for earlier flowers than if started indoors in spring. Whichever you sow this fall, both lead to hassle-free color come next growing season.
4 Reasons to Sow Perennials in the Fall
Hassle-free stratification: Some perennials' seeds need stratification-periods of cold temperatures combined with moisture (like that from snow and rain during winter) to break a natural dormancy, allowing them to germinate. Take advantage of nature's process by sowing in the fall, or mimic winter conditions by using your refrigerator (read more about this method).
Earlier blooms and larger plants: Perennials live for more than two years, and can take several years to get to their mature size. By sowing perennial seeds in the fall, plants will be more mature the following year than if spring sown, allowing many types to flower their first growing season.
Care-free moisture management: Most regions have winter rain and/or snow, providing essential moisture without you lifting a finger. Cool weather also reduces the need to water as frequently, when rain and/or snow is not adequate.
Control weeds with ease: Cool weather slows weed germination and growth, making your nicely prepped and sown garden area easier to maintain in the upcoming season.
Tips for perennial success:
Sow perennials that do not need stratification at least 8 to 10 weeks before your average first fall frost. This allows time for the seed to germinate, and plants to establish a root system large enough to survive the winter. Remember that in late summer heat seeds may need water twice a day to avoid drying out.
Sow perennials that need stratification after a hard, killing fall frost. This ensures that they will not sprout until the following spring.
Mark the spot. Label the area of sown seeds with garden stakes.
In a dry winter be sure to water late summer and fall-sown perennial seeds just as you do your trees.
3 Reasons to Sow Annuals in the Fall
Earlier blooms: Select annuals, when fall sown, will emerge as soon as Mother Nature cooperates, allowing the plants to germinate and bloom earlier than spring-sown annuals.
Robust plants: Direct sowing, when possible, results in the most robust plants. When seeds are started indoors they are a bit spoiled by even, moderate temperatures, and refined growing medium. Transplanting usually results in some transplant shock, while new root growth navigates native soil and plants get used to temperature swings in their new home.
Ease: Skip the indoor lighting, potting, and care that come from growing transplants by direct sowing. Some gardeners find they have more time in the fall, rather than spring, so sow a little extra to enjoy next year.
Tips for annual success:
If you live in an area with frost and snow, sow the seeds after a killing freeze but before snow (late October, early November in most areas), or you can also sow in late winter between snows. The snow helps bury seeds and insulates them, helping to retain moisture. In southern states and other mild winter areas, you can sow in late September for cool weather blooms this winter.
Mixing a little sand with the seeds not only helps space seeds more evenly, but also gives you a better visual aid of where you sowed in case you need to water over a dry winter.