How To Plant And Grow Gorgeous Cosmos Flowers
Cosmos are easy-to-grow cut flowers that overflow with soft, billowy petals.
With their romantic shades of pink, white, and red, these vibrant annuals are a sight to behold in any cut flower garden.
These lovely bloomers are a true cut-and-come-again flower, and they are drought-resistant once established!
My children and I sprinkle cosmos seeds into the garden every spring. In a few months, we are rewarded with rows of gorgeous flowers and colorful bouquets.
Let me show you how to grow these irresistible cut flowers!
About
Here are a few important facts about cosmos:
- Grows in zones 2-11
- Primarily grown as an annual
- Latin name: Cosmos bipinnatus
- Germination time: 7-21 days
- Originated from Mexico
- Meaning: Represent harmony, peace and love
- Colors: white, pink, red, orange, yellow and black
Feature these stunning annuals in cottage-style flower beds, cutting gardens, containers, and informal flower beds
How To Grow Cosmos For Cut Flowers
Cosmos are easy-to-grow cut flowers that will bloom prolifically.
Don’t be shy when harvesting the flowers for indoor display. Cutting the flowers with a long stem will encourage the plant to branch out laterally, growing more blooms.
The cosmos plant will become more robust and vigorous as you harvest. Plan on cutting flowers for vase display at least once per week.
This bushier plant will produce hundreds of flowers up until the first frost of fall.
Keep reading to learn about the best light, fertilizer and soil for these gorgeous bloomers.
Direct Sowing Cosmos
Sew cosmos by seed after all danger of frost has passed in moderately fertile to poor soil. (Make sure to choose a well-draining, sunny location).
First prepare the soil by loosening it with a rake, removing any large clumps or rocks. Sew the seeds about 3 inches apart. Gently water.
Once seedlings emerge, thin so the plants are 12-18 inches apart.
Dwarf varieties grow just 12 inches tall and can thrive in pots and containers.
Light
Cosmos flowers need plenty of ample sunlight and can handle heat. Choose a location with at least 6 hours of sunlight per day, preferably more if available.
If not given enough light, these plants will develop long, leggy stems as they stretch for the sun. They will also produce fewer flower blooms.
Water
When it comes to watering, think deep and infrequent, not often and shallow!
Give cosmos flowers a deep soak once or twice a week. In scorching weather, increase watering to support the plant.
Soil type may affect how frequently you need to water. Heavy clay soils will hold water, while sandier soils allow moisture to escape more quickly.
Always aim your water wand at the plant’s roots, especially when it is a young seedling. Use a gentle flower of water so you do not displace the soil and expose the plant’s roots.
Cosmos will wilt a bit when thirsty; this is their silent way of saying, “Hey! I’m thirsty!”. Just give them a deep drink and they should perk right back up.
Soil
Cosmos can tolerate in various soil types, but loose, sandy soil is their favorite. (Because of this, they make a great companion plant for lavender).
The most essential feature in this plant’s soil is how well it drains: they must have soil that drains quickly. Avoid soggy, damp soil at all costs.
Use compost to increase drainage and break up heavy clay soils.
Fertilizer
Cosmos plants do not need fertilizer! Overfertilization can cause problems for your plant.
Too many nutrients will cause this plant to have weak stems and sparse flower buds. If too much nitrogen is present in the fertilizer/soil, the plant foliage will grow aggressively, and the blooms will suffer.
Pinching
When the plant is young, you can pinch out the center growth tip to encourage a bushier plant with lots more flowers.
To do this, find the center stalk that is growing and pinch or cut it at the first set of leaves.
You will be rewarded with a bushier, healthier plant loaded with flowers.
Deadheading For More Blooms
When properly deadheaded, these cutting flowers will bloom abundantly all summer long and well into the fall months. (They will bloom right up until frosts hit!).
To deadhead:
- Follow the spent bloom down to it’s first set of leaves.
- Use sharp scissors to cut the flower close to this set of leaves.
- Do not remove the flower head alone; the plant will not branch out and produce more buds.
Vase Life
Cosmos have a relatively short vase life, from 4-7 days. To prolong the life of the cut flowers, harvest the blooms when they are swollen buds- just about to open.
Many new flower gardeners make the mistake of harvesting their flowers when the bud is fully open- this robs you of several days of bloom time!
Make sure to give your flowers water with flower food and set them in a cool place out of direct sunlight.
Pests + Diseases
Cosmos are relatively hardy and low-maintenance. That being said, they can fall prey to a few pests and diseases:
Thrips and aphids are the most common plants that prey on the leaves of these beautiful flowers.
Thrips will appear as tiny black dots lining the leaves of the plant. You can easily remove these pests with a spray hose.
Aphids are sap suckers and will suck the life from your plant, distorting the leaves. Consistent use of neem oil will keep aphids at bay.
You can also deter these pesky bugs by planting flowers that naturally repel insects, like marigolds and chrysanthemums.
