Trio of Cosmic Yellow Cosmos on a white background.
Cosmos Seeds, Cosmic Yellow
Cosmic Yellow Cosmos arranged on a stone background.
Cosmic Yellow Cosmos in an arrangement surrounded by blooms on blue background.
Close-up macro detail of Cosmic Yellow Cosmos flowers.
Nine Cosmic Yellow Cosmos flowers surrounded by petals on blue background.
Cosmic Yellow Cosmos in a bright shiny yellow metal cup with blooms on light background.
Trio of Cosmic Yellow Cosmos on a white background.
Cosmos Seeds, Cosmic Yellow
Cosmic Yellow Cosmos arranged on a stone background.
Cosmic Yellow Cosmos in an arrangement surrounded by blooms on blue background.
Close-up macro detail of Cosmic Yellow Cosmos flowers.
Nine Cosmic Yellow Cosmos flowers surrounded by petals on blue background.
Cosmic Yellow Cosmos in a bright shiny yellow metal cup with blooms on light background.

Cosmos Seeds,
Cosmic Yellow

52 ReviewsSKU: #FL434Min. seed count: 30
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Description

(Cosmos sulphureus). These care-free buttercup yellow blooms will add a splash of sunshine to the landscape … and for minimal effort! These 1- to 2-foot tall plants are rugged and reliable. Smothered in semi-double to double 2-inch wide blooms. Pollinators will flock to any bed, border, container, or meadow that cosmic yellow grows in.

Growing Tips: Cosmic Yellow cosmos is a heat-loving, drought-tolerant heirloom variety. It thrives in hot, dry conditions and poor to moderate soil. It attracts bees, butterflies, and other beneficial insects while requiring minimal maintenance. Keep the plants deadheaded for continuous blooms.

Plant Details

Botanical Name
Cosmos sulphureus
Life Cycle
Annual
Sun Requirement
6–8 hr.
Days to Germinate
7–14
Days to Maturity
50–60
Planting Depth
⅛–¼ in.
Plant Spacing
10 in.
Ideal Temperature
65–85°F
Frost Hardy
No

When to Grow

Plant Cosmic Yellow cosmos after the last frost, when soil temperatures reach at least 60 F. Alternatively, you can start seeds indoors 3-4 weeks before the last frost. Since it is sensitive to frost, check your local last frost date before direct sowing or transplanting seedlings outdoors. This variety begins to bloom 50-60 days after sowing and will continue flowering until the first frost. Learn more about frost dates by checking out our blog post, 'Our Experts Answer Questions, Share Resources.'

How to Sow and Plant

Sow seeds 1/8-1/4 inch deep in well-draining soil and press them lightly into the surface. Do not bury them too deeply, as cosmos seeds require light to germinate. Space plants about 10 inches apart for good airflow. Germination takes 7-14 days at temperatures between 60-75 F. If starting indoors, be careful to transplant only when the temperatures are consistently warm.

How to Grow

Make sure that the plant receives 6-8 hours of full sun every day. It is drought tolerant once established and should be watered only when the soil is completely dry. Overwatering can weaken the plant and lead to leggy growth. Too much nitrogen will cause excessive foliage growth and fewer flowers, so avoid excessive fertilization. In windy locations, light staking may be needed for support.

How to Save Seeds

  • Cosmos are insect pollinated, and there may be some crossing between varieties in the garden. You can enjoy the mixing or use caging techniques and hand pollination to avoid crossing.
  • Saving seeds from cosmos is easy: simply allow the heads to brown and dry on plants and collect seeds. Store in a cool, dry, dark place over winter.

FAQ

Can Cosmic Yellow cosmos be grown in pots?

Yes, it is an excellent choice for container gardening. Use a well-draining pot and avoid overwatering.

Why are my Cosmic Yellow cosmos plants not flowering?

Too much nitrogen in the soil can encourage excessive leaf growth at the expense of blooms. Make sure that your cosmos receives 6-8 hours of direct sunlight daily and avoid rich fertilizers.

How long does Cosmic Yellow cosmos bloom?

It blooms continuously from midsummer until the first frost. Deadhead the plants regularly to encourage better flowering.

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