As you might know by now, I mostly grow vegetables. A lot of them! But I also adore flowers. My seedbox is like a large palette with plenty of colorful options I can use to decorate my kitchen garden. I just love watching the flowers bloom. Garden cosmos (like in the picture above) might be the most beautiful flowers I know of!
Can You Winter Sow Cosmos? A Guide to Getting an Early Start on Beautiful Blooms
Cosmos is a beloved flowering annual that brings vibrant pops of color to summer gardens with its bright, cheery blooms While you can directly sow cosmos seeds in the garden after the last spring frost, starting them ahead of time using winter sowing allows the plants to get a head start on growing This means you can enjoy cosmos flowers much earlier in the season.
Winter sowing, also called winter seed sowing, is an easy and low-cost way to germinate seeds like cosmos during the colder months. With just a few basic supplies, proper timing, and the right conditions, winter sowing cosmos can provide an abundance of blooms in your garden by mid-summer.
What is Winter Sowing?
Winter sowing refers to the process of sowing seeds outdoors during the winter months. It takes advantage of natural winter conditions to naturally stratify seeds and promote earlier spring germination.
The basic winter sowing method involves sowing seeds in containers that are left outside throughout winter. The containers protect the seeds from animals and severe cold while still exposing them to the moist, cold conditions that naturally occur in winter.
This cold moist stratification helps break seed dormancy, resulting in earlier and often higher germination rates once warmer spring weather arrives. It’s an easy, passive way to get a head start on the growing season.
Why Winter Sow Cosmos?
There are a few key reasons why winter sowing is a great technique for cosmos
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Cosmos seeds require cold stratification to break dormancy and germinate well. The cold, wet conditions of winter provide ideal natural stratification.
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Winter sowing gives cosmos seeds a head start on growing, allowing earlier blooms by mid-summer.
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It’s an easy, low-cost way to start cosmos without the need for grow lights or a greenhouse.
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Winter sowed cosmos transplants are hardened off and acclimatized for planting out.
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You can get larger quantities of transplants to create a bigger impact of color in the garden.
Tips for Successful Winter Sowing of Cosmos
Follow these tips for best results winter sowing cosmos:
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Choose appropriate cosmos varieties for your growing zone. Look for early bloomers.
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Start the winter sowing process in late winter or early spring based on your climate.
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Use containers with drainage holes and seed starting or multipurpose potting mix.
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Sow seeds shallowly, 1⁄8 inch deep and lightly cover with soil.
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Water minimally over winter, taking care not to saturate or drown seeds.
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Provide protection from extreme cold but still expose to chilly temps.
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Allow natural stratification for 8-12 weeks for optimal germination.
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Harden off and transplant after all danger of frost has passed.
Step-by-Step Guide to Winter Sowing Cosmos
Follow these simple steps for successfully winter sowing cosmos:
Gather Needed Supplies
- Seed starting mix or multipurpose potting soil
- Containers with drainage holes – yogurt cups, plastic pots, etc.
- Cosmos seeds
- Small scoop, spoon or stick for planting seeds
- Clear plastic dome lids or plastic wrap
- Spray bottle for watering
- Optional: Straw, bubble wrap for insulation
Prepare the Containers
- Fill containers nearly to the top with moistened seed starting mix.
- Gently firm the mix without packing it down too much.
Sow the Seeds
- Sow 2-3 cosmos seeds per cell, 1⁄8 inch deep.
- Gently press seeds into the mix and cover lightly with more mix.
Water Sparingly
- Mist soil lightly until moist but not saturated.
- Place dome lids to retain moisture.
Shelter Outdoors
- Set containers in a sheltered, sunny spot like a porch or cold frame.
- Insulate with straw or bubble wrap in extreme cold if needed.
Allow Natural Stratification
- Leave containers undisturbed for 8-12 weeks for natural winter conditions to stratify seeds.
Transplant Seedlings
- Carefully transplant seedlings after hardening off for 7-10 days when frost danger has passed.
Enjoy Early Blooms!
- Water and care for transplants and enjoy earlier cosmos blooms!
The extra time winter sowing provides lets the plants establish and grow stronger for better blooms that you’ll enjoy all season long. It’s an easy way to get a head start on growing cosmos from seed.
Other Flowers to Winter Sow
In addition to cosmos, here are some other flowering annuals and perennials that do well with winter sowing:
- Snapdragons
- Poppies
- Calendula
- Bachelor’s buttons
- Sweet peas
- Marigolds
- Zinnias
- Petunias
- Lavender
- Salvia
- Daisies
The key is choosing cold-hardy varieties suited to your climate. Check seed packets for suitable planting times and directions. With the right flowers, winter sowing makes starting a cutting garden or flower border easy.
Get an Early Start with Winter Sown Cosmos
By exposing seeds to natural winter conditions, winter sowing cosmos and other flowers allows for earlier spring germination and healthier, more vigorous plants. This means you’ll be rewarded with earlier and longer-lasting blooms.
If you’re eager to get a jump on the growing season, winter sowing is an effective way to start cosmos and other annuals from seed. The extra time pays off with robust transplants and gorgeous blooms you’ll enjoy all season!
Winter-sow to save time
I try to give myself a head start in spring by preparing all the seeds I can sow outdoors in winter. It might seem illogical or possibly impossible to do, but you can actually start sowing flowers in winter. A good benchmark to remember is that most of the flowers that self-sow have hardy seeds that can survive in (or on top of) the soil during winter. Those of you who know your gardens might be aware of which flowers these are. If you dont know for sure, you could always look at the back of the seed packets and pick the seeds that you can sow in around October-December.
Where should I sow?
OUTSIDE – Scatter the seeds in, for example, your flower beds and put a little soil on top. The plants start to grow and bloom in spring.
CULTIVATION BOX OUTSIDE – Sow the seeds sparsely in a marked space in your cultivation box. Cover with a lid or fabric, or leave it as it is. Move the plants outside when they have grown large enough. The sowings in the cultivation box arent as well protected as the seeds in the polytunnel or miniature greenhouse and they will start growing later in spring.
BEDS IN THE POLYTUNNEL/GREENHOUSE – Use the same method as when you want to sow outside. Sow the seeds in a limited and well-marked space in one of the beds in your polytunnel or greenhouse. The seeds grow quicker here than outside and you can move the plants outside when its warm enough.
POT/TROUGH – Sow the seeds sparsely in a pot filled with soil in winter, and leave the pot outdoors (preferably in a shady spot.) The soil will get watered by the rain and the seeds start to grow. Just make sure that the pot doesnt get too wet since this might affect the soil and seeds in a negative way.
POT/TROUGH IN A PLASTIC CONTAINER – Follow the steps above but put the pots in a plastic container with holes in the bottom and the lid, in a shady spot outdoors. The plastic container turns into a miniature greenhouse that will protect the seeds in spring and give you an earlier harvest than the two other options above.
When Im sowing flowers this way, I always count on that the results will be slightly less satisfying than when I do more controlled sowings in troughs and then replant them later. The flowers I choose to grow now are generally the varieties I have plenty of seeds for at home. I gathered some of them by myself or bought seed packets that contain hundreds of seeds in each packet.
How to Winter Sow Cosmos | Perennial Garden
FAQ
Are cosmos good for winter sowing?
If the packet says “sow after danger of frost has passed” this is your time to winter sow these seeds. Examples include beans, black-eyed susan vine, cardinal vine, cosmos, cucumbers, parsley, zinnia and many more.
Can you just scatter cosmos seeds?
Cosmos are some of the easiest and most productive flowers to grow. They don’t need to be started inside, you can simply scatter the seeds, keep them damp, then watch them explode!
How late can I plant cosmos seeds?
| Plant name | Zone | Start seeds outdoors (spring/fall) |
|---|---|---|
| Cosmos | 9a | Jan. 15-Feb. 15; Sept. 15-Oct. 30 |
| Cosmos | 9b | Jan. 15-Feb. 15; Sept. 15-Oct. 30 |
| Cosmos | 10a | Jan. 15-March 15; Sept. 15-Oct. 30 |
| Cosmos | 10b | Jan. 15-March 15; Sept. 15-Oct. 30 |
Can you winter sow zinnias?
Technically, yes, you can winter sow zinnias, but it’s not advised. These are warm-weather plants. They need warm soil to germinate, and they don’t require cold stratification.