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Growing Cosmos From Seeds in Kingston, Ontario

Simon's background is in biomedical and health science. He also writes about fashion, nature, and photography.


I was first introduced to Cosmos back when I was a teenager. I was visiting my cousins in Eugene, Oregon, and we were on a walk through their neighbourhood. My cousins pointed out these pretty flowers growing in someone's garden. I instantly fell in love with them.

There are two reasons why I wanted to grow Cosmos in our front yard garden. The first reason was to have beautiful flowers to decorate our house. The second reason was to have them as subjects for my photography.

It was in elementary school where I first attempted to grow anything from seeds. Our project was to grow bean plants indoors. That was the first time I ever sow anything and watch it grow. Today, I wanted to try growing Cosmos from seeds.

Cosmos Background

Cosmos originally came from the southwestern United States and Mexico. Now, they are widely available in North America. They come in many different sizes, shapes, and colours. Cosmos are annual plants that love full sun. They can survive in partial shade but with fewer blooms. They can grow from three to six feet in height. The flowers bloom from July to frost, and attract bees, butterflies, and birds to your garden.

Cosmos seeds

Package of Cosmos seeds

Package of Cosmos seeds

The seeds

In late April of this year, I bought a package of Cosmos seeds from Canadian Tire. The company that produced them was McKenzie. They are a Canadian company based in Brandon, Manitoba. The seeds were fairly cheap at $1.89/pack with about 15 seeds. When I opened the package, I found that the seeds were small, elongated and brown. They almost looked like miniature slim, brown bananas. The package labelled them as "Early Sensation Mix," consisting of crimson, rose, pink and white flowers with yellow centres.


I had to do research on when was the best time to sow the seeds. All the websites that had information about sowing Cosmo seeds said to do it after the last day of frost. I had to go to the Old Farmer's Almanac's website to look up the last day of frost for Kingston, Ontario. It turned out that the last day of frost was April 26. Just to be sure that there was a lower chance of frost, I planted the seeds a few days later. I can't remember the exact date that I sowed the seeds. It was either April 30th, May 1st or May 2nd.

I didn't prep or condition the soil that was in the garden. There were small pebbles as well as grass and weed in it. I tired to remove much of the the grass and weeds as I could. Other than that, I didn't do much to the soil.

The instructions on the package said to sow them at a depth of 6mm or 1/4 inch with 2.5cm or 1 inch spacing. Using a trowel, I carved out a very swallow line in the soil, which I estimated to be about 6mm deep. Then I tossed the seeds in and covered them with soil. I gave them some water, and that was the sowing process.

Danger of Frost

A few days after planting the seeds, the weather got colder. We actually had a few days of frost warnings where the temperature dropped close to 0oC. I was worried that my germinating seeds were going to die because of the colder temperatures.

However, and thankfully, they didn't die. After about two weeks, I saw a small Cosmos seedling. I was so ecstatic that the seeds germinated and grew. I knew it was a Cosmos plant because the shell of the seed was still attached to the leaflet. Please see the attached image.

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Cosmos seedling after two weeks

Cosmos seedling with the seed shell still attached

Cosmos seedling with the seed shell still attached

Distinctive Leaves Showing

We received a lot of rain during May. There was even more rain in April. So much so that there was flooding in certain parts of the city. With that much rain, I didn't have to water the seedlings very often. On one or two days in May, I gave them some water as the soil was dry and cracking. That was the most I had to do. The Cosmos seem to grow quite well with little attention given to them.

After nearly a month of growing, I could see the fine distinctive thread-like leaflets growing out of the seedling. Please see the attached image. I also discovered that there were a few other Cosmos seedlings in the garden. This meant that there were more than one seed that germinated. I was so happy to see that I had about four Cosmos plants growing.

Cosmos after nearly a month


Cosmos on June 1st (one month)

Their distinctive fine threadlike leaves can be seen

Their distinctive fine threadlike leaves can be seen

First Flower

I was afraid that these Cosmo plants would not grow big enough to produce flowers this growing season. Surprisingly, they did produce flowers! I'm happy to say after about three months, two plants flowered. They are still small at about 6 to 7 inches tall, but they bloomed. Hopefully, they will get bigger and produce more flowers as the summer progresses.

First Flower in Mid-July

First flower of the season

First flower of the season

Final Bloom

It is now late September. Fall is here now. Soon we will have frost, which will end our growing season.

Two out of the four Cosmos died over the summer. There is really just one healthy plant left. It bloomed a few days ago. This is likely the last flowering of the season (see the photo below). It was a beautiful flower with five petals. I'm sad that the season is ending.

Final Bloom

Bloom in late September

Bloom in late September

Final Words

Out of the 15 or so seeds that I planted only four germinated and grew into small plants. Two of the plants flowered, giving rise to pretty purple flowers. The other two eventually died over the summer. They didn't grow as big as I wanted them to. They only reached about 8 inches. I've seen other gardens where the Cosmos are 3 or 4 feet high. To be fair, I didn't do much to them. I never gave them water or fertilizer. They seemed to survive all right on neglect. Maybe I need to start them much earlier or use fertilizer. That will be something I could do next year. For now, I'm happy with how they turned out even if I only got a small growth.

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