Sowing Seeds: The Basics of Seed Starting
If you are planting a garden this year, now is the perfect time to start browsing and shopping for seeds, as we have just under 6 weeks until the last average frost (for Michigan). In this post, I’m going to share some basic information about annual seeds, along with a few resources that helped me plan out a seed sowing schedule for the spring. You can sow seeds directly into the ground in the late spring, or whenever the soil and air are warm in your climate. But, if you’re interested in starting seeds early, you should consider the following before you head out to the garden: The hardiness of the annual, local growing zone and frost dates, and the type of sowing method that the annual prefers.
The hardiness of the annual
Annual seeds can be classified into three groups: Hardy, semi-hardy, and tender. These classifications indicate the level of frost tolerance the seeds can withstand, and ultimately when and how you should sow them.
Hardy annuals
Annual seeds that are classified as hardy are able to withstand some frost and might even make it through the winter to the following spring. This sounds like a perennial, right? As confusing as it might be to a new gardener, the hardy term is specific to the cold tolerance, not the growth tolerance. Hardy annuals are planted in the fall or early spring, thus, can handle a bit of frost. They are different from perennials in that they only complete one growth cycle, whereas perennials can bloom for multiple years.
Examples of hardy annual seeds:
Bachelor button
Dusty Miller
Calendula
Viola
Snapdragons
Pansy
Sweet pea
Dianthus
These hardy annuals, or ‘cool flowers’, are best planted directly into the ground letting cool temperatures establish them. In colder climates, start hardy annual seeds in late winter indoors, and plant them outside 4-6 weeks prior to the last spring frost. One of the best things about hardy annuals is they produce blooms much earlier than other seed types, prolonging your garden’s bloom time.
2. Half-Hardy Annuals
Half-hardy annuals can tolerate light frosts but shouldn’t be planted outdoors until the risk of frost has completely passed. These should be planted in late spring or early summer. If you want to get a head start, half-hardy annual seeds can be sown indoors as early as March to bloom by early June.
Examples of half-hardy annual seeds:
Cosmos
Geranium
Petunias
Marigold
Amaranthus
Nasturtium
3. Tender annuals
Tender annuals can not tolerate any frost and require warm air and soil to grow. These seeds are sown outside in late spring, or indoors 4-5 weeks before the last spring frost.
Examples of tender annual seeds:
Morning glory
Zinnia
Sunflower
Begonia
Coleus
Salvia
Impatiens
Growing zone
It’s important to know what specific climate you live in because it will help determine what plants you can grow in your area, and for how long. Use a climate zone map to find out your hardiness zone number. My specific city in Midwest Detroit is hardiness zone 6b. When I’m shopping for seeds and plants, I check the description to see what zone range is recommended.
USDA zone system rule of thumb: The higher the number, the longer the growing season. Understanding your growing zone makes planning seed sowing much easier, as some annuals need frost and others are frost-free. Speaking of frost dates…
Frost dates
Not everyone will have the same sowing date due to varying climates. Finding the first and last frost date for your specific location is the first step in planning your seed sowing journey. Knowing your location’s frost dates will allow you to map out a plan for each type of annual you want to grow. For example, seed packets generally include planting instructions on the back of the packet: “plant 4-5 weeks before the last average frost”. There are wonderful tools online that provide these specific frost dates based on zip code, which will help you fill in the blanks. This is my favorite one.
Where I live, I have a risk of frost until May 6th. It’s safe for me to (trans)plant outside May 19th through September 26th.
Sowing method
There are dozens of intricate sowing methods for technical gardeners. I’m going to share with you 3 basic seed sowing methods for home gardening. Essentially, the type of annual seeds you choose matched with the growing zone you live in, will result in one of the following recommended sowing methods:
Direct sow: planting the seeds directly into the ground outside during a specific time of year.
Indoor sow: planting seeds in small containers (or flats) indoors, during a specific time of the year.
Transplanting: taking seeds that have been sown indoors and planting them outside into the ground after a certain amount of time.
For instance, Zinnias are a tender annual that should be sown indoors in early April and transplanted outside in May, or direct sown outside in mid-late May (Michigan, growing zone 6b). If I lived in California (growing zone 10), I would start sowing Zinnias indoors in late January, and transplant them into the ground late February- Mid April.
Making a plant plan
I didn’t plant anything my first year gardening (last year) because I was waiting to see which perennials had already been planted. Now that I know what lies beneath the soil, I can plan out what I want my garden to look like, and which flowers (annuals) I want to plant. I spent most of the last summer logging when each flower bloomed so I could create a garden plan with overlapping blooms.
This year’s sowing plan:
Zinnias indoor the week of April 19th, transplant May 24th
Cosmos indoor April 3rd, transplant May 15th
Nasturtium direct sow May 24th
Sunflowers direct sow May 24th
Dusty Miller indoor March 21st, transplant May 24th
Morning Glory direct sow May 15th
Asters inside March 22nd, transplant May 2nd
Calendula inside March 22nd, transplant May 2nd
Nigella Damascena direct sow May 19th
Bachelor’s Button inside March 21st, transplant May 2nd
I can’t wait to plant these annuals from seed and share the growth progress! I’ll have more pictures and updates come spring, so stay tuned!
This year I purchased my seeds from Eden Brothers and Botanical Interest