How to Grow Cosmos Flowers

Cosmos are a summer-blooming annual native to Mexico. They are colorful daisy-like flowers with yellow button centers that grow 2 to 4 inches in diameter. Cosmos flowers are available in various colors, making this popular, easy-care flowering plant a garden favorite.

Are cosmos easy to grow?

Cosmos flowers are super easy to grow. They tolerate poor soil, are bothered by few pests, and self-sow in the garden.

What bloom colors are available?

The plant’s name comes from the Greek word “kosmos,” meaning beautiful. Cosmos cultivars include single, double, and semi-double flowers in a wide array of colors, including:

• White
• Red
• Pink
• Yellow
• Orange
• Red
• Deep Brown-Red (Chocolate)
• Bicolor

What planting zones are best for cosmos?

• Common Cosmos (Cosmos bipinnatus) grow best in planting zones 2 to 11.
• Chocolate Cosmos (Cosmos atrosanguineus) grow best in planting zones 7 to 9.

This also depends on the particular variety you wish to grow. Check the seed packet for planting zone recommendations.

Do cosmos attract butterflies, bees, and other beneficial insects?

Yes. If you love butterflies, cosmos flowers will attract butterflies, bees, and moths to the garden.

Cosmos Flower Care

Soil Requirements – Cosmos will happily grow in poor soil, but average well-draining soil is best. Avoid planting cosmos in rich, fertile soil. Cosmos prefers neutral to alkaline soil pH levels.

Sun Requirements – Cosmos prefer a spot where it can receive full sun – at least six hours per day.

Moisture Needs – This summer bloomer prefers evenly moist soil but will happily grow in dry soil. Cosmos is perfect for arid locations, as it is considered drought-tolerant.

Fertilization – Feed plants with compost or an all-purpose fertilizer, once during mid-summer. Adding fertilizer too often will lessen the number of flowers.

Pests and Disease – Cosmos have no significant diseases or insect problems but keep an eye out for:

• Aphids
• Stem canker
• Powdery mildew
• Gray mold

Does cosmos grow well in planters?

Cosmos grow equally well in garden beds or containers. Plant cosmos seeds or seedlings in a 3-gallon or larger container.

How long do cosmos flowers bloom?

Cosmos blooms from early summer to frost. During the heat of late summer, you may notice less blooming. Trimming spent flowers can increase bloom time.

When should I plant cosmos?

Sow cosmos seeds in the garden just before the last spring frost date or start seeds indoors 6 to 8 weeks before the last spring frost date. Transfer seedlings outdoors after the last spring frost.

Grow cosmos in a sheltered location, away from strong winds.

Does Cosmos self-seed?

Yes. While pruning spent flowers, leave some spent flowers on the plants to self-seed. The spent flowers will dry and distribute seeds throughout the garden, thus creating new plants next spring.

Where should I grow Cosmos?

Cosmos is a showy, blooming annual plant with fern-like foliage. Cosmos usually grow from 2 to 4 feet in height, depending on the variety.

This summer bloomer is beautiful when grown in:

• Mixed beds and borders
• Cutting gardens
• Cottage gardens
• Naturalized gardens

Taller cosmos cultivars look best in the back of the garden and pair well with phlox, foxgloves, delphiniums, poppies, cleome, and daisies.

In addition, dwarf cosmos cultivars pair well with zinnias, morning glory, Johnny-jump-ups, pansies, and alchemilla.

Enjoying Cosmos Flowers

Trim cosmos flowers when the blooms have just opened. Then, remove the lower leaves from stems and place flowers in a vase filled with water. Your bouquet should last a week or more.

Did you know? Chocolate Cosmos flowers smell just like chocolate! Create a chocolate-themed garden by planting chocolate cosmos, black salsify, and chocolate mint. Add cocoa bean mulch for more chocolate aroma.