Popular Self-Sowing Annual Flowers

Growing annual flowers offers two advantages over growing perennial flowers. First, annuals bloom profusely throughout the growing season. Second, many favorite annual flowers freely self-sow and weave their way through your garden year after year. Self-sowing flowers are what we refer to as "volunteers." They do the work for you, and no flowers do it better than annuals.

Only open-pollinated and heirloom varieties of any plant will grow true from seed, meaning the seedlings will be exactly like the parent plants. (A pink hybrid geranium will give you white or red geraniums the following year, for example.) But there are many open-pollinated, self-seeding annuals to choose from, and even if you do get some unexpected seedlings, who's to say you won't like them? That's where new plants come from.

When growing self-sowing annual flowers, you need to allow the late-season blooms enough time to go to seed. If you've been deadheading all summer to keep the blooms coming, stop deadheading by the middle of August. The seeds need to ripen, and that usually means the flowers must dry completely. That's about all it takes. They don't call them self-seeders for nothing. Other fall bloomers in your garden will have to distract you from the browning annuals. If nature cooperates, you'll be seeing volunteers in and about your gardens next year and for years to come.

Sowing Seeds Yourself

Annuals that have self-seeded give your garden a natural look. However, sometimes they seed too enthusiastically or plant themselves where you wish they hadn't. Fortunately, self-sown annuals are easily transplanted to other spots in your garden or potted up for friends. Or you could take matters into your own hands and simply save the seeds and sow them yourself the following year instead of letting nature take care of the propagation. Then, either scatter the seeds directly into the flower bed or start the seeds indoors next spring.

If you choose to direct seed your own annual flowers, be sure you know and provide the conditions the seeds require to germinate, including:

• Light: Some seeds need light to germinate and should not be covered with soil. Scatter these seeds and lightly press them into the soil with the back of a hoe or a board. Other annuals require darkness, which can be easily achieved with a top layer of soil.
• Scarification: Several annual flowers protect their seeds with hard coverings. To improve the odds of these seeds germinating, scarify, or nick, the outer covering by rubbing with sandpaper or chipping the coating with a sharp knife. Use caution with the knife method. These seeds are hard and tiny, and it's so easy to miss. It's easier to soften the seed by soaking it overnight.
• Cold: Besides moisture, some annual flower seeds, such as poppies, require a period of cold before they are triggered to begin germination. Nature takes care of this for us when the seeds are left on the ground during winter. If you are starting seeds indoors, place the potted seed in the refrigerator in a baggie for the recommended amount of time or in the garage, depending on the temperature. This is called stratification.

When to Sow Outdoors

When to sow annual flower seeds outdoors depends on the type of seed and your climate. The best indicator is nature. If certain annuals reliably self-sow in your garden, you can bet they prefer being sown in the fall. Annuals that disappear after a season could simply be sterile hybrids, or they may prefer warmer germination conditions. For example, you can save seed from many marigolds, but it is rare for them to self-sow in cold climates.

USDA Hardiness Zones 5 and Lower
Short-season gardens stand the best chance of getting a lot of self-seeded volunteers during winters with good snow cover, for insulation from the cold, drying winds. Obviously, only seeds that can handle a period of cold are going to self-seed in these gardens, and you will need to ensure that you have allowed the seed heads to mature before your first frost. The option of saving seed and direct sowing it in the garden in the early spring, just before you expect the frosts to subside, might work best for gardeners in colder zones.

USDA Hardiness Zones 6–8
Those of you in moderate zones have the best of both worlds. You have a longer period in the fall to allow seeds to ripen and drop. You also probably get enough of a cold spell for seeds that need a chill to germinate.

USDA Hardiness Zones 9–11
Gardeners in zones 9 and higher can also allow seeds to self-sow in the fall. But your annuals will likely grow and flower in winter, rather than waiting for spring. Unless your weather is very dry, you will probably get several seasons of volunteers.