7 Tips for growing cosmos from seed successfully

This spring and summer i am going to make gardening my whole personality. I am definitely in my garden girl era. I have gardened for the last 10 years but this year feels different. I feel like i am so filled with knowledge and i want to start sharing that with you 🌷

Proof of the tomatoes with snow outside!

Back in November i ordered two different types of cosmos seeds, the Apricotta and Apricot Lemonade variety. I also got sent some seashell cosmos mix for free and they are currently germinating in a Costco croissant container in my sunniest windowsill.

I like to experiment with different seeds and try new ways of growing. Over the winter as a homeschool experiment, my children and i grew tomatoes and it worked! So many people told us it wouldn’t but, we had a winter full of fresh tomatoes. It was great!

I always like to say that gardening is 30% method and 70% energy ✨

There is something that is so magical about growing something from seed and if you are looking for a flower that is easy and rewarding, cosmos, should be at the top of your list.

Cosmos are loved for their soft, romantic petals, and cottage garden like charm. They are so pretty. They thrive in warm sunshine, attract pollinators, and bloom for months with little care. They are one of the simplest flowers to grow from seed, making them perfect for beginners.

Here are 7 simple tips to help you grow cosmos from seed successfully this season.

Start with quality cosmos seeds

The first step to success is to choose high quality seeds. Cosmos seeds are easy to recognize, they are long, thin, and pointed.

Pictured above are the ones i ordered from a shop on Etsy, the packaging is beautiful. You can shop them here.

Some popular cosmos varieties you may want to try include:

• Cosmos bipinnatus - classic pink, white, and magenta blooms.

• Cosmos sensation mix - Tall with large flowers.

• Cosmos cupcake variety - Unique petals that form a delicate cup shape.

• Cosmos sulphureus - Vibrant orange and yellow flowers.

Cosmos are annual flowers, which means they grow, bloom, produce seeds, and complete their life cycle in one season. However, they often self seed, meaning you may find new plants popping up in your garden next year.

Plant cosmos seeds at the right time

Timing plays an important role in growing cosmos successfully.

Cosmos are warm season flowers that love sunshine and warm soil. They don’t tolerate frost well, so soil needs to be planted after the last frost in your gardening zone.

If you live in a cooler climate like me, cosmos seeds are usually best planted directly outside after last frost, or late May to June.

You can also start them indoors 5 - 7 weeks before the last frost, but cosmos grow so quickly you might prefer to direct sow. Once the temperatures warm up, seedlings will grow really quickly.

Choose a sunny location

Cosmos really thrive in lot’s of sunlight.

For the healthiest blooms, plant cosmos in areas that receives at least 6 - 8 hours of direct sunlight per day. The more sun they get, the stronger and more abundant blooms will be. If planted in too much shade, plants may grow tall and weak with few flowers.

Don’t over enrich the soil

The tip that surprises people the most is cosmos actually prefer poor soil. Don’t run out and grab the best quality soil!

While most flowers thrive in rich compost filled beds, cosmos grow best in light, well draining soil that is not overly fertile.

If the soil is too rich, the plants may grow:

• fewer flowers

• Lots of leaves

Cosmos are naturally adapted to thrive in average garden soil. This makes them low maintenance and perfect for beginners.

Simply loosen the soil before planting, remove weeds, and lightly rake the surface.

Direct sow seeds for the best results

Although i have some cosmos seeds germinating in a Costco croissant container, cosmos seeds actually prefer and do better when they are directly sown into the ground.

Here is a simple method:

1. Loosen the soil in your chosen area.

2. Scatter the seeds lightly across the surface.

3. Cover the seeds with about a quarter of in of soil.

4. Water gently.

Seeds usually germinate with 7 - 10 days when the temperatures are warm. Once seedlings appear, thin them so that plants are spaced about 12 to 18 inches apart. This gives them room to grow tall and full.

Many gardeners love scattering cosmos seeds along garden beds for that cottage garden look.

Water lightly but consistently

Young cosmos seedlings need moisture to sprout.

After planting seeds:

• Keep soil lightly moist until germination.

• Avoid soaking the soil.

• Water gently to avoid disturbing seeds.

For my seedlings, i will be lightly misting every other day. Once plants mature, cosmos are surprisingly drought tolerant. Over watering can lead to weaker plants.

Deadhead for endless summer blooms

One of the best things about growing cosmos is their long blooming season. With little care, they bloom from early summer until the first frost.

To encourage more flowers regularly deadhead the plants. Deadheading means removing faded flowers before they produce seed.

This signals the plant to create more blooms instead of seed heads. Simply snip off the faded flower just above the next set of leaves. This will give you continuous blooms all summer long!