Growing Cosmos from Seed

Cosmos are colorful flowers to enjoy for just a season, but a worthy visitor to any garden. Get tips for growing this popular annual from seed.
gby1306_2a_cosmos_big_bloom

gby1306_2a_cosmos_big_bloom

Related To:

If you're a gardener who thinks annuals aren't worth the effort because they're relatively short-lived, here's a flower that's out of this world. Derived from the Greek word meaning "beautiful," cosmos are as dainty as they are durable and are also one of the easiest plants to grow from seed.

Once upon a time, back when gardeners planted seeds, nurtured seedlings and watched them grow into stunning beauties, cosmos swayed proudly in gardens across the land. Then along came the era of instant gratification with already-blooming flowers and container gardens, and things that don't transplant well — like cosmos — fell from flowering favor.

But in true fairy tale fashion, where patience is a virtue and old things become new again, cosmos are enjoying a renaissance among seed-sowing gardeners. A prolific bloomer, cosmos transplants can grow much too large in tiny nursery pots and become root-bound. The easiest, cheapest and perhaps most satisfying solution is to plant a seed and watch it grow.

Before planting, read the seed packet directions carefully. There are a couple of sowing methods. The first, slide a one-by-one stick or ruler across the soil to form a shallow trench and plants according to the instructions. Then pinch the soil over the seeds and applies lightly press it firmly in the ground. Finally, give the seeds a gentle drink of water.More relaxed gardeners can use the second, less fussy, planting method. Just shake, scatter and sow. Rub soil between your fingers over the seeds to cover them evenly.

Cosmos are adaptable to almost any kind of soil, but they do need moisture to germinate. In dry, hot climates, place a shade cloth over the bed until the seedlings begin to sprout. This happens in roughly five to 10 days after planting.

Cosmos bloom continuously until the first frost. With its distinguished forms and vibrant colors, it's no wonder why so many gardeners are over the moon for these flowers in their landscaping, even those with small yards.

Cosmos will only grow to about 21 to 22 inches, and they're perfect as part of your landscaping or container gardening. While compact Cosmos sulphureus are great for container gardening, Cosmos bipinnatus reaches six feet or higher with a tendency to topple over.

To keep your cosmos in bloom, keep them trimmed. Take a branch with many finished flowers, go a third of the way down the plant and cut. Pruning is an easy way to prompt new growth and tidy up the plant. Afterward, fertilize, water and await a whole new crop.

As generous reseeders, you can either save the seed for next year's garden (remove the dried flower heads to get the seeds) or let nature scatter the seeds for you.

Keep Reading

Next Up

Growing Petunias

When it comes to sun and soil, petunias can't get enough of the good stuff.

Lantana Care: Growing and Pruning Lantana

Add easy-care beauty to your yard by growing lantana—you won’t be disappointed.

Growing Stewartia

Enjoy the blooms of this “false camellia” all summer long.

Growing Cut Flowers

Extend the enjoyment of your garden to the indoors.

Growing Carnations

Try your hand at growing these floral favorites.

Growing Mums

Learn tips for planting and growing beautiful, healthy garden mums.

Balloon Flower Growing Tips

This hardy perennial is a prized medicinal plant in the Far East.

Growing Phlox

Learn how to grow this perennial charmer for your summer garden.

Planting and Growing Yarrow

Learn what you need to know about growing yarrow.

How To Choose, Plant And Grow Annuals

Add a burst of seasonal color to your garden with easy-to-grow annuals.

1,000+ Photos

Browse beautiful photos of our favorite outdoor spaces: decks, patios, porches and more.

On TV

Tiny House Hunters

6:30am | 5:30c

Flea Market Flip

8:30am | 7:30c

Flea Market Flip

9:30am | 8:30c

Flea Market Flip

10:30am | 9:30c

Flea Market Flip

11:30am | 10:30c

Fixer Upper

12pm | 11c

Fixer Upper

1pm | 12c

Fixer Upper

2pm | 1c

Fixer Upper

3pm | 2c

Fixer Upper

4pm | 3c

Fixer Upper

5pm | 4c

Fixer Upper

6pm | 5c

Fixer Upper

7pm | 6c
On Tonight
On Tonight

Fixer Upper

8pm | 7c

Good Bones

9pm | 8c

House Hunters

10:30pm | 9:30c

House Hunters

11pm | 10c

House Hunters

11:30pm | 10:30c

Good Bones

12am | 11c

House Hunters

1:30am | 12:30c

House Hunters

2:30am | 1:30c

Fixer Upper

3am | 2c

Follow Us Everywhere

Join the party! Don't miss HGTV in your favorite social media feeds.