How to Grow Cosmos: The Whimsical Flower That Never Gives Up!
It isn’t hard to learn how to grow cosmos! These whimsical flowers can grow in almost any soil, grow like weeds, and they are great for beginners. Not to mention the many varieties, you are sure to find cosmos you will fall in love with.Ho
How to Grow Cosmos Summary:
- Soil: Break up your soil and get rid of any weeds or grass. If needed add a layer of compost.
- Plant the seed ¼ inch deep and put 2-3 seeds in each hole. Space your planting 8-12 inches apart. I plant mine 9 inches apart because I like a full look.
- Water: Keep the ground damp, but not pooling water until the seedling comes up.
- Continued Care: Water regularly, especially when they are young and establishing roots. Once about a foot tall Deep water once a week at the base of the plant. Water 2-3 times a week during hot summer spells.
For more detail, my favorite variety, and common questions read below!
1. Choose the Right Location
Cosmos need full sun to thrive, so select a spot that gets at least 6-8 hours of direct sunlight a day. They prefer warm, well-draining soil.
2. Prepare the Soil
Prepare your soil by clearing any grass or weeds. Then loosen your soil with your hands or shovel.
Cosmos are not too fussy about soil quality, but they grow best in well-draining soil. You can improve your soil by mixing in some compost if your soil is dense and hard. If your soil is sandy or very loose, adding some compost will help retain moisture and provide nutrients.
3. Growing Cosmos From Seeds
- When to Plant: Plant cosmo seeds after the last frost in spring when your night temperatures are no lower than 32 degrees. Your last frost date can be found with a simple google search.
- Direct Sowing: Plant the seed ¼ inch deep and put 2-3 seeds in each hole. I like to use the back of a sharpie for the perfect hole. Plant seeds 8-12 inches apart.
- Water: Keep the ground damp, but not pooling water until the seedling comes up.
- Start Indoors: You can start cosmos indoors under grow lights 4 weeks before your last frost date to get a head start on the growing season.
4. Watering
Cosmos need regular watering, especially when they are young and establishing roots. However, they do not like to sit in waterlogged soil. Water the base of the plant to avoid wetting the foliage, which can lead to fungal diseases. Deep watering once or twice a week is typically enough, but in hot weather, they may need more frequent watering such as every other day or every day.
5. End of Season Care
Cosmos are annuals. At the end of the season, you can collect seeds from the flowers to plant the following year. Simply let the flowers dry on the plant, and when the flower heads are completely dead and dry, collect the seeds from the center of the flower and store them in a cool, dry place. FREE SEEDS!
Show Stopper Cosmo Varieties:
Cupcake white- These cosmos have a beautiful pleated edge and have petals that look like cupcake liners!
Double Click Rose Bon Bon- These are my favorite cosmos with many ruffly petals and the perfect pink color.
Sea Shell- These cosmo petals really do look like seashells, and come in a range of pink and white colors.
Candy Stripe- These cosmos have a beautiful outline to the petals. So pretty!
Frizzy Rose Picotee- These white and pink flowers have almost feather looking petals on the inside.
Cosmo Garden Ideas
Cosmo can be so fun because they grow so tall you can use them like a wall by…
- Plant them on a fence line for privacy
- As a backdrop for pictures or up against your home
- Planted as a hedge
Common Questions
How do I keep Cosmos blooming all summer?
Keep cutting the flowers! Even if you let some flowers die on the plant, cut them off for the plant to put more energy into growing more flowers and not grow seeds.
How tall do cosmos grow?
Depending on the variety cosmos can grow 1-6 feet tall! If you want shorter cosmos get the container or dwarf variety.
Do cosmos come back every year?
No, cosmos are annuals. You will need to replant every spring.
What temperature will kill cosmos?
Cosmos are frost sensitive. When night temps are below 32 degrees they will die.
Do Cosmos need full sun?
Yes, Cosmos need 6-8 hours of full sun.
What month do you plant Cosmo seeds?
Plant cosmo seeds after the last frost in spring when your night temperatures are no lower than 32 degrees. Usually anytime April-July, but check your weather and last frost date to be sure.
What happens if you plant Cosmos too close together?
If planted to close the plant will not grow as large.
Where can I buy Cosmo seeds?
Anywhere you can buy seeds you can get Cosmo, but my favorite places to get unique varieties are
Johnny’s Select Seeds
TrueLeaf market
Botanical Interest
Baker Creek Rare Seeds
If you want to know the other flowers to grow for an abundant cut flower garden click HERE!
As always,
Grow flower to heal your soul,
Beth
