Most annual flowers are easy to grow from seed. The real challenge is figuring out when and where you should plant the seeds. People often find themselves at home with a stack of colorful seed packets and no idea where to begin.
Seed packets rarely provide the basic seed-starting information a gardener needs to know. The packet usually won't tell you whether the seeds should be started indoors under lights or planted right in the garden. You won't be told if the seeds need light or darkness to germinate or if the seedlings are frost-hardy. With so many unusual varieties available from seed, you may also wind up purchasing seeds for something exotic, like the Himalayan Blue Poppy (Meconopsis betonicifolia), that even a highly experienced gardener would have difficulty bringing into flower.
To ensure your success right out of the gate, start with some super-easy seeds (Sunflower, Marigold, Morning Glory, Bachelor Button Zinnia, or Calendula). Then, give yourself a year or two with these foolproof favorites before you venture into growing some of the more challenging annuals in the next list.
No matter what kinds of annuals you grow, here are a few things you might want to know before getting started:
- What size are the seeds? This may seem like a peculiar concern, but if you're going to plant your flower seeds directly into the garden or put individual seeds into peat pots, the seeds need to be large enough to handle. Dust-like seeds (such as Petunias and Snapdragons) will get lost if you try to direct-sow them (plant them right into the garden).
- Are there any special germination requirements? Though most seeds prefer to germinate in darkness, some require the lights on. Sometimes seeds (such as Lupines, Sweet Peas, and Morning Glories) have very tough seed coats and should be soaked or nicked before planting. Some seeds will also take their time germinating. While most will be up in four to 7 days, for some, it's normal to take 3 to 4 weeks to get going.
- How rapidly will the seedlings grow? This is tricky because the growth rate is genetically programmed but is also influenced by growing conditions. For example, plants grow much more rapidly in an 80 degrees Fahrenheit (27 degrees Celsius) greenhouse than under a grow light in a cool basement. Some annuals, such as Impatiens, will be a good size for transplanting when they're about eight weeks old. But if you start your Zinnias eight weeks before transplanting, they'll be root-bound and too tall when they go into the garden. Most gardeners sow fast-growing annuals, such as Sunflowers, Bachelor Buttons, Calendulas, Zinnias, and Nasturtiums right into the garden. I agree that it's not worth growing these seeds indoors for just 3 to 4 weeks and running the risk of transplant shock.
- How long will it take from germination to bloom? The seed packet should tell you how many "days to bloom," which means how long it takes from germination to flowering. For example, if you have a short growing season and the packet says it will be 80 or 90 days to bloom, you will need to start the seeds indoors if you want to see them flower for a couple of weeks before frost. The easiest annuals to start from seed usually come into flower quickly, often blooming just 50 to 70 days after planting.
- How cold-hardy are the plants? Seeds of hardy annuals can be planted directly in the garden as early in the spring as the soil can be worked. Once the seeds have germinated, the young plants will usually tolerate a light frost and temperatures down to 25 degrees Fahrenheit (-4 degrees Celsius). Half-hardy annuals can be started indoors 6 to 8 weeks before transplanting or planted right in the garden once the soil has begun to warm up. Most will tolerate a light frost, but be prepared to protect young seedlings if temperatures drop. Tender annuals can be sown directly in the garden, but only after all danger of frost has passed. These cold-sensitive seeds can also be sown indoors 4 to 6 weeks before the last spring frost. Transplant into the garden when you are confident that nighttime temperatures will stay above 40 degrees Fahrenheit (5 degrees Celsius).
If you are interested in starting lots of annual flowers from seed, consider investing in a seed-starting reference, such as Eileen Powell's excellent book: The Gardener's A-Z Guide to Growing Flowers from Seed to Bloom. This book describes more than 500 different types of flowers and how to grow them. In addition, you'll find important information about germination requirements, plant hardiness, time to bloom, etc. The more you know, the better you'll grow.
- Plantpedia: Browse flowering plants by Scientific Name, Common Name, Genus, Family, USDA Hardiness Zone, or Origin