We have all seen the effects of fall sown flowers in the garden - that over enthusiastic cleome that comes up in the area where you grew it last year, or the surprise tomato plants that appear in the vegetable garden where last year you grew cherry tomatoes. All these seeds are sown by your flowers every fall and wait until spring before they germinate. Replicating what nature does saves windowsill space next spring as well as giving those cool weather plants an extra early start in the garden.
The best seeds to sow outside in fall are those that bloom early in the year. Many of these are 'cottage garden' plants such as lupines or poppies, but it also works for many varieties of annuals, biennials and perennials that sow a few seeds each year. Sometimes the annual varieties are called ‘hardy annuals’ which are true annuals but reappear reliably each year.
Gather the ripened seed from your annuals or order your selected seeds in October or November and note the general growing conditions such as whether the plants grow best in full sun or a shady place in the garden. Wait until the ground is cool enough to plant spring bulbs – around 55°, or cool to touch. Prepare the area just as you would for spring planting by removing any stones and raking the garden smooth. Most seeds prefer to be covered by a layer of soil, but check the packet to see if your seeds prefer light to germinate. Cover with a little mulch to stop birds and rodents eating them. You do not have to water the seeds when you plant them because over the winter, nature will provide plenty of moisture for them.
Let the seeds stay in the ground over winter and watch for the seedlings to arrive next spring. In most cases the seedlings arrive and begin happily growing several weeks before you can safely transplant seedlings that you have started indoors.
Good varieties to pick are those that you have noticed reseed by themselves or those that bloom before the heat of summer arrives. Cleome, Cosmos, Delphinium, larkspur, Pansies, and annual Poppies are just a few of the great varieties that you can sow in late fall or early winter.
Don't forget - in the vegetable garden you can sow garlic cloves, onion seeds in fall too!