Cosmos is a flowering warm-season annual commonly grown from seed. A staple of cottage-style borders, cosmos produce cheerful daisy-like flowers from summer into fall. Even beginner gardeners will enjoy success with this easy to grow flower.
Though individual flowers last just several days, the buds are produced in clusters along the stems for long-lasting color in beds, borders, containers, or cut flower arrangements. Here’s how to grow and use cosmos plants in your yard.
Cosmos is a warm season annual that is grown from seed or starts. Chocolate cosmos is a tender perennial grown from tubers or seed.
Most cosmos are annual in all zones. Chocolate cosmos is a tender perennial hardy in USDA zones 7-11.
Daisy-like flowers 2 to 5 inches wide have single, double, semi-double, or fluted petals encircling a yellow or brown center. The blooms occur in colors of white, pink, magenta, burgundy, yellow, orange, apricot, or chocolate, with some bicolored or multi-colored. Petals can be rounded, ruffled, or fringed.
Cosmos are one of the most beloved annual flowers for gardens, and for good reason. Their bright and cheery daisy-like blooms on tall, slender stems create clouds of color from early summer well into fall. Plus, cosmos are extremely easy to grow right in garden beds and require minimal care. Read on to learn insider tips for planting cosmos in beds to enjoy their beauty all season long.
Why Grow Cosmos in Beds?
There are many great benefits to incorporating vibrant cosmos into flower beds around your yard and gardens
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Provide continuous pops of color from midsummer into fall with their exceptionally long bloom period. The flowers just keep coming once they get going!
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Attract beneficial pollinators like bees, butterflies, and hummingbirds. Cosmos are a fantastic nectar source for pollinators.
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Available in many heights and flower colors to fit any garden design need. Pick dwarf, mid-size, or tall varieties.
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Extremely unfussy and durable annuals. Cosmos tolerate heat drought poor soils, and other stresses but still thrive and bloom.
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Gorgeous cut flowers to create fresh-picked bouquets for indoors. A vase of cosmos instantly brightens up a room.
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They readily self-sow so may come back year after year with zero extra effort on your end.
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Tall cosmos add nice vertical interest against fences, trellises, pergolas and as backdrops when allowed to grow upwards.
Plan Your Cosmos Bed
Taking the time to properly prepare will set your cosmos bed up for success. Follow these planning tips:
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Sun Exposure – Select a location receiving at least 6 hours of direct sun daily. Cosmos thrive in full sun.
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Soil Conditions – They perform well in average soil and even poor soils, but ensure adequate drainage. Lightly amend dense clay or sandy soils with compost.
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Spacing – Allow 10-12 inches between dwarf cosmos varieties. Give taller types 18-24 inches of space to spread out.
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Supports – Add trellises, cages, stakes and other supports for taller cosmos to climb up and prevent flopping over later on.
When to Plant Cosmos
Cosmos can be directly seeded into garden beds during either spring or fall:
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Spring – The most popular planting time. Sow seeds directly outside after the final spring frost date passes for your zone.
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Fall – To get a jump start on next year’s blooms, sow seeds in autumn after the first few light frosts hit. This winter sows them.
For both cases, wait until soil has warmed to at least 60-65°F before sowing since cooler soils hinder germination. Use a soil thermometer to check.
How to Direct Sow Cosmos in Beds
One of the easiest flowers you can grow, cosmos seeds simply get scattered right on top of the soil. Just follow this planting process:
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Prep beds by raking smooth, removing weeds/debris, and mixing in compost if needed.
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Sow seeds by scattering evenly over soil surface and pressing down lightly. Cover extra small seeds with 1/4 inch layer of fine soil or compost.
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Gently water after planting to moisten soil. Mist occasionally until seedlings emerge.
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Thin young plants to proper spacing distances once the first true leaves appear.
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Provide 1 inch of water weekly if rain is lacking. Avoid overhead watering that wets foliage.
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Apply 1-2 inch organic mulch layer around plants to retain moisture and reduce weeds.
And that’s really all there is to it! Cosmos are so ridiculously easy and carefree to grow from seed. Now just wait patiently for those colorful blooms to start appearing in around 8-10 weeks.
Growing and Maintaining Cosmos All Season
Here are some care tips to keep your cosmos bed looking its best over the growing season:
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Pinch or cut back young plants by 1/3 when 8-12 inches tall to encourage bushy, compact growth habit.
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Insert stakes or plant cages early on for taller varieties to avoid toppling from rain and wind later in season.
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Deadhead spent blooms regularly to extend flowering. Pinch off old flowers just above new buds.
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Provide supplemental watering if rainfall totals 1 inch per week. Water at base of plants, not from overhead.
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Carefully weed around cosmos when young and refresh mulch midseason with 2-3 inch layer.
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Apply light fertilizer, if any at all. Too much nitrogen results in leafy growth instead of flowers.
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In hot climates, cosmos may appreciate a bit of afternoon shade to protect from intense sun exposure.
Which Cosmos Varieties to Select
Many cosmos cultivars exist, including:
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Picotee – White petals with pink or crimson ring around edge. Very striking!
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Sea Shells – Unique tubular ray florets in white, pink or red.
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Purity – Classic, snowy white blooms that pair nicely with darker flowers.
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Sonata Mix – Excellent dwarf cosmos type ideal for containers. Long blooming.
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Chocolate – Rich maroon flowers with a delicious vanilla-chocolate scent.
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Sensation Mix – A diverse blend of bright colored blooms on tall plants.
Tips for Using Cosmos in Garden Designs
Cosmos offer endless possibilities for garden designs thanks to their range of heights and colors:
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Use short varieties like Sonata Mix in container plantings, herb gardens, and border fronts.
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Allow taller cosmos to grow against fences, trellises, and as backdrops to highlight their height.
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Underplant cosmos with shade tolerant annuals like impatiens that share similar watering needs.
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Mass single color cosmos together for high visual impact.
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Allow cosmos to self-seed and enjoy their spontaneous appearance each year.
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Combine cosmos with other pollinator-friendly blooms like zinnias, marigolds, salvias, and more.
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Mix and match hues for a vibrant, rainbow-colored flower bed or border.
Caring for Cosmos All Season Long
Proper care throughout the seasons will keep your cosmos working their magic in garden beds:
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Spring – Sow seeds or plant transplants after final frost. Pinch young plants to encourage bushy form.
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Summer – Water during dry periods, stake tall varieties and deadhead spent blooms. Enjoy the show!
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Fall – Allow some flowers to go to seed for self-sowing next year. Pull plants after heavy frost.
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Winter – Scatter reserved seeds in garden beds in early spring to perpetuate flowers.
Harvesting Cosmos Flowers and Seeds
One of the best benefits of growing cosmos is getting to harvest all those beautiful blooms:
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Snip fresh flowers for bouquets by cutting stems when blooms are partially open using clean, sharp pruners.
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Start by cutting stems a bit longer than needed, then trim to desired size for arranging.
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Remove any leaves that would sit below the water line in the vase.
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Change water and re-cut stems every 2-3 days to extend vase life up to 10 days.
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Deadheading spent blooms also counts as harvesting flowers and promotes more blooms!
Are Cosmos the Right Flower for Your Garden Beds?
If you are searching for a tough, prolific and low maintenance annual flower that pollinators adore, then cosmos should absolutely be on your must-grow list! These vibrant daisy-like blooms are ideal for beds, borders, containers, and cutting. Just sprinkle those cosmos seeds over prepared soil this spring and you’ll be rewarded with armloads of beautiful blossoms until cold weather arrives. Cosmos are a true warm-season garden staple.
Benefits and other attributes:
Cosmos flowers are attractive to butterflies and other insect pollinators, while the seed heads are a food source for songbirds and other wildlife. Cosmos may reseed themselves in the next growing season, though some hybrids may not come true from seed.
AnnualsDiscover the right annual plants for your garden.
Candy Stripe cosmos flower. Photo by: Janet Loughrey
Cosmos is a flowering warm-season annual commonly grown from seed. A staple of cottage-style borders, cosmos produce cheerful daisy-like flowers from summer into fall. Even beginner gardeners will enjoy success with this easy to grow flower.
Though individual flowers last just several days, the buds are produced in clusters along the stems for long-lasting color in beds, borders, containers, or cut flower arrangements. Here’s how to grow and use cosmos plants in your yard.
On this page:
Cosmos is a warm season annual that is grown from seed or starts. Chocolate cosmos is a tender perennial grown from tubers or seed.
Most cosmos are annual in all zones. Chocolate cosmos is a tender perennial hardy in USDA zones 7-11.
Upright or mounding branching habit
1 to 5 feet tall, 1 to 3 feet wide
Green foliage can be ferny, deeply dissected, or lance-shaped, depending on the species.
Daisy-like flowers 2 to 5 inches wide have single, double, semi-double, or fluted petals encircling a yellow or brown center. The blooms occur in colors of white, pink, magenta, burgundy, yellow, orange, apricot, or chocolate, with some bicolored or multi-colored. Petals can be rounded, ruffled, or fringed.
Best Companion Planting Flowers for the Vegetable Garden
FAQ
Are cosmos good for the garden?
It attracts butterflies and is easily used as an attractive border or backdrop plant. Cosmos is simple and easy to grow from seed sown in the spring, readily reseeds itself, and tolerates a wide range of soil types.
What not to plant next to cosmos?
Companion Planting with Cosmos
Cosmos don’t attract many pests – except aphids. Sometimes cosmos are put to work in the garden by drawing aphids away from other plants, a method known as decoy planting. For example, plant cosmos away from your prized roses.
Where should cosmos be planted in the garden?
Cosmos flower best when planted in full sun and in free-draining, average garden soil. Plants in shade will also struggle to flower.
Can you plant cosmos next to tomatoes?
Plants recommended for companion planting with tomatoes include amaranth, asparagus, basil, bean, borage, calendula (pot marigold), carrots, celery, chive, cleome, cosmos, cucumber, garlic, lemon balm, lettuce, marigold, mint, nasturtium, onion, parsley, peas, sage, stinging nettle, sow thistle, and squash.
Are Cosmos easy to grow?
Yes cosmos are easy to grow. ‘Cosmos is one of the easiest flowers to grow from seed that is directly sown in the garden bed,’ advise the experts at American Meadows. ‘As they grow, stake cosmos if necessary, and water them regularly,’ says Sarah Raven. Cosmos suffer from few pest problems.
How do you use Cosmos in a garden?
Versatile: Cosmos can be used in a variety of ways, from adding color to a mixed border or flower bed to filling in gaps in a garden to providing a backdrop for other plants. Long-lasting blooms: The flowers typically bloom from summer to fall, providing a long-lasting source of color and interest in the garden.
How much sun does a cosmos plant need?
Be sure that your cosmos garden beds receive full sun. These plants will bloom best where they can receive at least 6-8 hours of direct light each day. Though they can tolerate less, too much shade may result in tall or leggy stems as well as poor flower production. A tender annual, cosmos cannot tolerate cool temperatures.
What is a cosmos plant?
Cosmos bipinnatus: Also known as the Mexican aster or garden cosmos, this is the most commonly grown species. Plants typically grow to a height of 2-5 feet (60 to 180 cm) and produce large, daisy-like flowers in a variety of colors, including pink, white, red, orange, and yellow.
Will Cosmos grow if left outside?
Cosmos is an annual. If left outside in frosty temperatures, they will die. However, at the end of the growing season, if you allow the dead flower heads to drop their seeds, cosmos seeds will go dormant and sprout when the soil warms up again in the spring.
Why should you grow Cosmos in your garden or landscape?
There are several reasons why you should consider growing cosmos in your garden or landscape: Beautiful and colorful flowers: Cosmos flowers are known for their striking colors and attractive appearance. They add a vibrant touch to any garden or landscape.