Cosmos, Cosmos spp., is a dainty summer-to-frost flower in the Asteraceae family.
Its cousins are the aster, chrysanthemum, coneflower, dahlia, and marigold. Most varieties grow as annuals in Zones 2 to 11, but some are perennial in Zones 9 to 11.
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Low-maintenance, sun-loving cosmos shows well in mixed beds, borders, butterfly gardens, containers, cottage gardens, cutting gardens, mass-planted drifts, and meadows.
Mature dimensions range from one to six feet tall and one to three feet wide.
Our cosmos growing guide provides all you need to know to grow your own.
This article discusses 19 of the best flowering companions to grow with cosmos. They share similar cultural requirements and look attractive when paired in garden settings.
Here’s what’s in store:
19 of the Best Cosmos Companions
Cosmos requires full sun and moderately rich, well-draining soil with a mildly acidic to mildly alkaline pH of 6.0 to 8.0.
Use soil tests to determine your garden soil pH levels. This may vary from one location to another.
The flora you select to grow near your cosmos should have similar needs.
Additional considerations when choosing garden mates are color, shape, and texture. Let’s quickly review each of these before we dig into the roundup!
If you grow pink, purple, or white cosmos, create a cool scheme by pairing it with flora in similar shades.
And if you prefer bright orange, red, or yellow cosmos, complement it with other boldly-hued flowers.
For an eclectic mix, display cool and warm colors throughout your landscape.
Mimic the rounded blossoms of cosmos with other daisy-like blooms, and vary or match the colors as desired.
Punctuate a floral display with spikes of clustered blossoms for vertical interest.
Add tubular forms to draw the eye into individual blooms.
Match cosmos’ delicate quality with other dainty blossoms and airy foliage.
Contrast the ephemeral quality with rigid spikes of blooms and darker, denser leaves.
Mix flora varieties to display various textures, such as papery, feathery, ridged, ruffled, serrated, smooth, and velvety.
Display variegated colors that highlight surface characteristics like veining.
Another essential when choosing companions is the size at maturity.
Consider height and spread as you design garden spaces, such as borders, containers, cutting gardens, drifts, meadows, and mixed beds.
Choose tall varieties for rear anchors, medium for mid-placement specimens, and low-profile for front-of-display ground covers.
For border gardens, varying the heights gives a sense of undulating waves and carries the eye pleasingly forward to each new crest.
And finally, consider bloom times to plan a season-long floral display.
Companion planting is a sensible way to garden.
By choosing varieties with similar sun, soil, and water requirements, you can rest assured that your selections will perform optimally, and you can use a one-size-fits-all watering scheme for easy care.
And now, 19 companions to love.
1. Bachelor’s Button
Bachelor’s button, Centaurea cyanus, is an annual that grows in Zones 2 to 11.
The thistle-like blossoms are predominantly blue but these are also available in pink, purple, red, white, and bicolor combinations.
Note that this species reseeds aggressively and returns as a perennial would. Planting it is prohibited in North Carolina and it is considered invasive in Tennessee, Maryland, and Georgia.
Mature dimensions are 12 to 36 inches tall and 12 to 24 inches wide.
This summer-blooming companion is suited to wildflower meadows or other naturalized planting areas that don’t encroach on farmers’ fields or suburban lawns.
C. cyanus ‘Blue Boy’ is a cultivar with double layers of petals in a rich gentian blue. Mature dimensions are 30 inches tall with a spread of 10 to 12 inches.
‘Blue Boy’ cornflower seed is available in packets of 150 from Burpee.
See our guide to growing cornflowers for more information.
2. Bee Balm
Bee balm, Monarda spp., aka wild bergamot, is a perennial native that blooms during the summer months in Zones 3 to 9.
It sports tubular, curved petals reminiscent of exploding celebratory fireworks.
Colors include lavender, pink, purple, and red. The upright stems reach three to five feet tall with a spread of 18 to 36 inches.
Bee balm is a wonderful meadow or drift companion that readily naturalizes.
Sugar Buzz® ‘Grape Gumball‘ Bee Balm
M. didyma ‘Grape Gumball’ from the Sugar Buzz® series is a cultivated variety with purple blooms that grows 18 to 24 inches tall with a spread of 18 inches.
Sugar Buzz® ‘Grape Gumball’ is available from Nature Hills Nursery in #1 containers.
See our guide to growing bee balm to learn more.
3. Black-Eyed Susan
Black-eyed Susan, Rudbeckia spp., is a US native wildflower. It’s a short-lived perennial in Zones 3 to 9 that blooms from summer to fall.
Petal-like rays surround a prominent black or brown center disk.
Cultivated varieties are available in various colors, including yellow, orange-yellow, orange, red, red and yellow, and yellow and white. The nectar and seed heads attract beneficial pollinators.
Plants have a mounding growth habit and naturalize readily. Mature dimensions are two to three feet tall and 12 to 18 inches wide. Plant en masse in cutting gardens, drifts, and meadows.
R. fulgida var. sullivantii ‘Goldsturm’ is a cultivated variety of native black-eyed Susan suited to Zones 3 to 9.
It has yellow rays around a black center disk and mature dimensions of two to three feet tall and one to two feet wide.
‘Goldsturm’ black-eyed Susan is available from Eden Brothers.
In addition to perennial black-eyed Susans, there are annual and biennial species in the Rudbeckia genus that make suitable companions as well.
Check out our guide to growing black-eyed Susans for more information.
Borage, Borago officinalis, is an annual herb for Zones 2 to 11 with a long history of use in traditional medicine.
Its starry blossoms are blue with white accents, or they may be all white. They bloom in the summer.
Borage self-sows with vigor. It has a clumping growth habit and is suited to naturalized settings like drifts and meadows.
Mature heights are 12 to 36 inches with a spread of nine to 18 inches.
Borage seeds are available from Botanical Interests.
Our borage growing guide has more information.
5. Cardinal Flower
Cardinal flower, Lobelia cardinalis, is a native perennial for Zones 3 to 9 with upright red spikes that bloom from late summer to fall.
It adds heat to mixed groupings and complements orange, red, and yellow companions.
The spikes consist of multiple segmented tubular florets that cluster along the terminal ends of the stems.
The rich color and feather-like form resemble the northern cardinal, fondly known as the redbird.
Other flower colors are available and include pink, purple, and white. Mature dimensions are three to six feet tall and 12 to 24 inches wide.
The scarlet hue and tubular blossoms of L. cardinalis attract pollinators like butterflies and hummingbirds.
This species is suited to naturalized settings like butterfly and cottage gardens.
Cardinal flower plants are available from Burpee.
Learn more in our guide to growing cardinal flowers.
Dahlia, Dahlia spp., is a tuberous bulb that grows as a perennial in Zones 8 to 11 and an annual in other regions.
It blooms from midsummer through fall and boasts a varied palette of forms and hues. Dahlia tubers can also be lifted for replanting the following year in regions with cold winters.
There are single-flowering anemone, collar, or orchid styles and double-flowering ball, cactus, semi-cactus, decorative, peony, and pom pom styles.
A broad selection of colors and multicolor patterns are available in all shades but blue.
Mature dimensions vary by cultivar. Heights are nine to 60 inches with a spread of 12 to 24 inches. Dahlias look lovely in mixed beds, with the tallest in anchor positions.
‘Bishop of Canterbury’ is a semi-double peony-style cultivar with fuchsia to magenta blossoms. It blooms from midsummer through fall. Mature dimensions are three feet tall and 30 inches wide.
‘Bishop of Canterbury’ is available from Eden Brothers in packages of two, four, and eight tubers.
Our guide to growing dahlias has full cultivation details.
Delphinium, Delphinium spp., is a perennial for Zones 3 to 7.
It makes a striking vertical statement with upright blue, pink, violet, or white spikes of densely packed florets at the terminal ends of the stems.
Mature heights are two to six feet with a spread of two to three feet. Bloom time is early to mid summer.
Mass-plant in cutting gardens or scatter in drifts and meadows.
‘Dark Blue White Bee’ Delphinium
D. elatum ‘Dark Blue White Bee’ is a stunning deep blue to deep purple variety with white centers that resemble pollinating bees.
Suited to Zones 3 to 7, this potential companion achieves a mature height of two to three feet and a spread of 12 to 18 inches.
‘Dark Blue White Bee’ delphiniums are available from Nature Hills Nursery in #1 containers.
Learn more in our guide to growing delphiniums.
Dianthus (Dianthus spp.) may be perennial, biennial, or annual, depending on the species, and is suited to cultivation in Zones 3 to 9.
Plants have a clumping growth habit and boast flattened five-petal single or fully double blossoms with deeply fringed edges in shades of lilac, pink, red, white, and bicolor combinations.
They have a rich, spicy fragrance like cinnamon and cloves.
Dwarf varieties make eye-catching container plants, edging, and front-of-bed ground covers. Large cultivars show well as specimens in mixed beds, and mass planted in cutting gardens and naturalistic drifts.
Bloom time is generally in the spring, however, in cooler regions, some cultivars may bloom continuously or periodically from late spring to early fall.
Dianthus ‘Raspberry Surprise’ is suited to Zones 4 to 8. Its fragrant pink blossoms have burgundy center eyes, fully double petals, and a generous two-inch diameter.
Mature heights are 10 to 12 inches with a spread of 12 to 15 inches. Plants bloom in the spring.
‘Raspberry Surprise’ plants are available from Burpee.
You can learn more about dianthus in our growing guide.
Foxglove, Digitalis purpurea, is a biennial for Zones 4 to 9 that grows in year one and blooms from spring to summer in year two when planted from seed.
It has upright stalks with elongated floret clusters at the terminal ends. Please note that foxglove is toxic.
The varied color palette includes cream, pink, purple, red, white, and yellow. The tubular florets face downward and have deep throats that often display contrasting markings.
Mature heights are 18 to 60 inches with a spread of 12 to 18 inches. It’s an excellent back-of-bed anchor.
D. purpurea ‘Pam’s Choice’ is best suited to Zones 5 to 9. It has creamy white florets with throats splotched by rich, velvety burgundy. Plants top out at four feet with a spread of 18 to 30 inches.
‘Pam’s Choice’ is available from Burpee in bundles of four plants.
Learn more about how to grow foxgloves in our guide.
10. Globe Amaranth
Globe amaranth, Gomphrena globosa, is a short-lived perennial in Zones 9 to 11 and an annual elsewhere.
The rounded blossoms consist of stiff, papery, petal-like bracts that resemble a thistle. Colors include lilac, magenta, orange, pink, purple, red, and white.
Bloom time is from summer to frost. Globe amaranth has a mounding growth habit and mature dimensions of six to 48 inches tall and eight to 24 inches wide.
The bobbing heads add movement and whimsy to cottage gardens.
Rio Grande globe amaranth, Gomphrena haageana is a tender perennial species for Zones 9 to 11.
QIS Fiery Sunrise Blend Globe Amaranth
G. haageana QIS® Fiery Sunrise Blend offers a bold collection of oranges, yellows, and reds to complement brightly-hued cosmos for a mixed bed or border that sizzles in the summer sun.
Stems measure 24 to 26 inches tall at maturity.
QIS® Fiery Sunrise Blend seeds are available from Botanical Interests.
Learn more in our guide to growing globe amaranth.
Hollyhock, Alcea rosea, is suited to Zones 3 to 10, where it’s generally a biennial, growing in the first year and blooming in the second when propagated from seed.
It may also be a short-lived perennial. This species has blossoms like a rose of Sharon and brings to mind the fairytale Little Bo Peep’s sunbonnet.
Hollyhock blooms along upright stalks and is available in various colors, including black, burgundy, peach, pink, purple, red, rose, yellow, and white.
Bloom time is summer. Mature dimensions are three to nine feet tall with a spread of two to four feet.
Hollyhock is suited to anchor positions in beds that showcase mid-height and low-profile specimens.
A. rosea ‘Indian Spring’ offers pink, rose, yellow, and white blossoms. Mature heights are five to eight feet tall and plants spread 12 inches wide.
‘Indian Spring’ hollyhock seeds are available from Botanical Interests.
See our guide to growing hollyhocks for more information.
Larkspur, Consolida spp., is an annual in Zones 2 to 11. It has upright spikes laden with terminal floret clusters in shades of blue, purple, pink, and white.
Annual larkspur resembles perennial delphinium, but larkspur has feathery foliage, and the delphinium has lobed, palmate, or hand-like leaves.
Consolida is a spring-to-summer bloomer that measures three to four feet tall and one foot wide. Enjoy it mass-planted in cutting gardens or scattered in drifts and meadows.
C. ajacis Rocket Larkspur Tall Mix offers a sampler of blue, pink, purple, and white flowers that mature to four feet tall and two feet wide. These colors complement cool cosmos shades.
Tall Mix seeds are available from Eden Brothers.
Learn more in our guide to growing larkspur.
Liatris, Liatris spicata, aka gayfeather and blazing star, is a perennial in Zones 3 to 9.
It has upright stalks and a clumping growth habit. Dense, feathery florets cluster tightly at the terminal ends. Typically purple, it may also be lavender, pink, or white.
Liatris blooms from mid- to late summer on stalks reaching heights of two to four feet and 15 to 18 inches wide.
Use it as a dramatic punctuation in borders, drifts, and meadows, and as a specimen in beds.
Blazing star seeds are available from Eden Brothers in a variety of package sizes.
Learn more in our guide to growing liatris.
Petunia, Petunia × hybrida, is a perennial in Zones 9 to 11 and an annual elsewhere. It has open-faced, tubular blossoms with velvety petals and blooms from spring to fall.
Growth habits vary from mounding and upright to spreading and trailing. Grandiflora, floribunda, multiflora, and milliflora types are available.
Colors include blue, coral, magenta, pink, purple, red, white, yellow, and multicolor combinations.
Petunias achieve a mature height of six to 18 inches and spread 18 to 48 inches. They perform well in containers, window boxes, beds, and borders.
Trailing varieties that cascade from containers also make attractive ground covers for edging or front of bed and border placements.
SuperCal® ‘Premium Caramel Yellow’
SuperCal® ‘Premium Caramel Yellow’ is a unique hybrid of Petunia and Calibrachoa, aka million bells.
Abundant small yellow blossoms have rust-colored throat accents. Mature dimensions are 14 to 24 inches with a spread of 14 to 26 inches.
SuperCal® ‘Premium Caramel Yellow’ is available from Burpee in four-plant bundles.
Check our petunia growing guide to learn more.
15. Purple Coneflower
Purple coneflower, Echinacea purpurea, is a native perennial for Zones 3 to 8 with daisy-like flowers. With a long history of use in herbal medicine, it blooms from spring to fall.
The blossoms consist of pinkish-purple rays surrounding a firm, cone-like center disk that is brown to black.
Mature dimensions are two to five feet tall and 18 to 24 inches wide. It is suited to specimen planting in beds and borders, and mass-planting in drifts and meadows.
E. purpurea attracts a host of pollinating insects, such as butterflies. And expect feasting songbirds when the center disks run to seed at season’s end.
Purple coneflower seeds are available from Eden Brothers.
Cultivated varieties, as well as additional Echinacea species, are also available.
They broaden the color palette to include burgundy, lavender, pink, red, salmon, white, and yellow for even more options.
Learn more about growing coneflowers in our guide.
16. Roman Chamomile
Roman chamomile, Chamaemelum nobile, is a perennial with a history of use as an herbal remedy. It grows as a perennial in Zones 4 to 9 and an annual in other regions.
Chamomile resembles a daisy, but the white, petal-like rays are shorter, and the center disk is proportionately larger.
It’s a low-profile, ground-covering plant that blooms from summer to fall. Mature dimensions are three to six inches tall and six to 12 inches wide.
Chamomile is an excellent choice for front of bed and border placements and it may be used as a lawn alternative.
It serves as a worthwhile companion to cosmos as well as other plants by covering the ground and inhibiting weed growth.
Roman chamomile seeds are available from True Leaf Market.
See our guide to growing chamomile for more information.
Stock, Matthiola incana, aka gillyflower, is a perennial in Zones 7 to 10 and an annual in other regions.
It’s a late spring to early summer cottage garden classic in shades of apricot, lavender, pink, purple, red, white, yellow, and multicolor.
The florets are multi-petaled and loosely arranged on upright stalks. Plants may be columnar with one stem or sprays with multiple stems.
Mature dimensions are 12 to 36 inches tall and nine to 18 inches wide.
Stock is a member of the Brassicaceae or cabbage family. Plant it as a specimen in beds and borders where you can conveniently reach it.
Post-bloom, cut the spent flowers and foliage to the crown to prevent them from decaying in the summer heat and emitting a cabbagey odor.
Column Blend stock seeds are available from Botanical Interests.
This single-stem columnar mix supplies a rainbow of double-petal blossoms on 24- to 30-inch stems.
Sunflower, Helianthus annuus, is an annual for Zones 2 to 11 that blooms from spring to early fall. It is generally yellow but flowers may also be red.
The blooms may be as large as saucers. They are daisy-like and consist of rays surrounding a large, flat central disk of tiny blossoms. Heights range from one to 12 feet tall and staking is often required.
It’s helpful to note that the flower heads face east at maturity to take advantage of the sun’s warming rays.
Plant the tallest as back-of-bed anchors or stand-alone specimens. Smaller varieties are suited to mixed bed groupings.
H. annuus ‘Teddy Bear’ is a sunflower with fluffy yellow blooms that resemble pom poms. Mature plants measure two to three feet tall with a 14- to 16-inch spread.
‘Teddy Bear’ sunflower seeds are available from Burpee.
There are also native perennial species with more modest flower sizes that you can consider.
See our guide to growing sunflowers for more information.
Zinnia, Zinnia spp., is an annual for Zones 3 to 10.
It comes in an array of colors and multicolor combinations ranging from hot pink and lime green to red and purple, with double, semi-double, or single ruffled or smooth petals and a visible or obscured center disk.
Dwarf types are six to 12 inches tall, and standard varieties measure up to four feet tall, with a spread of one to two feet.
Plants have a mounding growth habit. Zinnias show well in beds, borders, drifts, and meadows.
‘Amethyst Treasure’ is a hybrid zinnia cultivar with magenta-purple fully-double blooms. The stems are 12 to 18 inches tall, and the plants are 14 to 18 inches wide at maturity.
‘Amethyst Treasure’ seeds are available from Burpee.
Learn more about zinnias in our growing guide.
Plays Well with Others
Cosmos is an amiable garden companion that brings a host of beneficial pollinators to the garden and supports biodiversity.
It is not a heavy feeder, so it doesn’t deprive fellow plants of nutrients, nor is it invasive, so it doesn’t crowd its neighbors.
With 19 exciting flowering options, it’s time to take out your garden planner and sketch a scheme for cosmos and its friends.
Think about color, shape, and texture.
Consider height and plan to place the tallest at the back of beds. Alternate short and tall specimens for undulating borders.
And space generously to accommodate mature dimensions without overcrowding.
Review bloom times and envision the garden from spring to frost with flowering plants to delight you and visitors to your home, including pollinators and other beneficial insects.
Do you grow cosmos? What other plants share the garden with it? Please post your answers in the comments section below.
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