Cosmea, garden cosmos

Cosmea, also known as garden cosmos, with its filigree flowers are among the most beautiful summer flowers. How to plant and care for the summer flowers.

Mar 03, 2021 11:03 am
readtime icon 8 Minutes
Growth type
  • one year old
Growth height (from)
from 50 cm to 120 cm
Growth width (from)
from 0 cm to 0 cm
Growth characteristics
  • upright
Flower color
  • red
  • pink
  • white
Flowering time (month)
  • July to October
Flower shape
  • Uniflorous
Leaf color
  • green
page format
  • fiddly
  • sunny to semi-shade
Soil type
  • sandy to loamy
Soil Moisture
  • moderately dry to fresh
ph value
  • neutral
Lime compatibility
  • lime-tolerant
Nutrient requirements
  • nutrient-rich
  • rich in humus
Decorative or utility value
  • Flower Decoration
  • non-toxic
Winter Hardness
  • frost-sensitive
  • Flowerbeds
  • Bouquets
  • flower meadows
  • Planters
Garden style
  • cottage garden
  • Flower garden
Bee Friendly
bee friendly plant

While many ornamental plants from South America have the proverbial fiery temperament, the Cosmea (Cosmos bipinnatus), also known as cosmea, native to Mexico and Brazil, strikes a quieter note. Its bowl-shaped blossoms are elegant beauties and have earned it the German name "Schmuck Korbchen" (jewel basket). The common Cosmea comes from the sunflower family and belongs to the botanical genus Cosmos, which has almost 30 species.


The fine-feathered foliage, the soft, tall stems and the delicate flowers that appear from July make the garden cosmos appear fragrant and light. The upright and thoroughly branched summer flower plant can reach heights of 19.68 to 47.24 inches, depending on the variety.


The characteristic pinnate leaves of the garden cosmos are quite delicate and up to 5.90 inch long. Many Cosmea varieties are slightly hairy.


The garden cosmos bears up to 3.14 inches large, bowl-shaped flowers with a yellow center. The color of the eight ray florets varies from white to pink to red. Newer varieties of Cosmea have now also produced yellowish and two-tone flowers. Cosmea's flowering begins in July and often lasts until October, with bees and butterflies like to visit the large bowl-shaped flowers.

Garden cosmos “Velouette”
The large ray florets of the “elouette” garden cosmos are striped in red and white.
Location and Soil

Cosmea grows best in a sunny location and in fresh to moist, loose soil. However, it grows in practically any potting soil that is not over-fertilized. When planting in a container, peaty rhododendron soil mixed with sand is ideal. Garden cosmos are not fond of semi-shady locations. They do not flower as abundantly as in a sunny location.

Sowing and Planting

Cultivating cosmos from seeds is child's play. It is sufficient to just place the seeds in the desired location in the beginning of May. However, if you want to see flowers before August, go for planting instead. For this purpose, starting in March, sow seeds in boxes with potting soil. After three to four weeks, prick out the sprouted seedlings of the garden cosmos individually into pots. A pricking wood, with which you can drill the planting holes and carefully pull out the tender seedlings from the seed tray, does a good job. In a bright location and cool temperatures of around 59 degrees Fahrenheit, strong young plants develop that can be planted in beds or planters from May. Maintain a planting distance of about 11.81 inches, because garden cosmos require sufficient space in the bed or pot.

Double-flowered garden cosmos
Double-flowered blossoms give the garden cosmos a fluffy appearance

Cosmos are not very demanding in terms of care, normal garden or potted plant soil are sufficient for them. On reaching maturity, they can cope well with temporary drought. However, you should regularly cut out all withered flowers in order to support a continuous re-flowering, which stops in fall due to frosty nights. Despite the height of 39.37 inches and more, the thin stems prove to be reliably stable and only need a support in particularly exposed locations. Cosmos in balcony boxes or pots require regular watering. In good garden soil, a cosmos does not need any additional fertilization. Cosmos bipinnatus is annual and not winter hardy.

Cosmos in a container
Cosmos also look great in a container. The container should be big enough
Where to plant

The elegant South American plant are very versatile and easy to combine with other plants. The different varieties of cosmos are ideal as filling plants in borders and in flower boxes. A familiar picture would be a cottage garden with blossoming garden cosmos, as their simplicity make them a perfect fit for the rural surroundings. A seed mix of different cosmos varieties is recommended for a colorful bloom. Pretty plant partners are not only zinnias and Dahlias, which are also native to South America, but also asters, common marigolds, delphinium, Phlox and African marigold (Tagetes). Thanks to special color selection, finely composed bed arrangements can also be planned with cosmos. It is worthwhile to search through the range of seeds from reputed providers for special features. A tried and tested group of varieties is “Sonata”, which is available both as a color mix and in individual colors. This cultivation is characterized by a lower growth height of 19.68 to 23.62 inches, which makes it ideal for planting pots and containers.

For a beautiful overall effect, it is best to place repeating groups of three to five cosmos plants. The flowers of the garden cosmos also work well as cut flowers In a bouquet the delicate flowers will last a particularly long time if you cut them while the inner yellow tubular flowers are still closed.

white cosmos in between colorful flowers
White cosmos look particularly classy and elegant when planted between colorful summer flowers

“Innocence” blooms white and is about 39.37 inches tall, so does “Roggli Red” with large, red flowers. “Gloria” has pink flowers with a crimson ring. The two-tone Cosmea variety “Sea Shells Red”, which flowers in purple and light pink, is also quite pretty. With a height of 27.55 inches, it is also suitable for the pot. In any case, it is worthwhile to marvel at the funnel-shaped rolled petals up close. “Double Click Rose Bonbon” produces pompom-like flower balls in a beautiful pink shade. The plants reach heights of 23.62 to 35.43 inches and have sturdy stems. “Picotee” fascinates with a fine magenta border on its white petals. Also at a height of 39.37 inches, it should be planted in an exposed space in the flower bed. “Sunset Yellow” amazes us with a shade of yellow that is unusual for the cosmos. Their flowering time begins a little later, but goes well into October. It grows to around 80 inches tall.

Colorful flower bouquets
Cosmos are wonderful as cut flowers in fine summer bouquets

Annuals usually ensure their survival in fall by self-sowing. Every year they surprise us by growing in different, sometimes extremely inhospitable locations. If you prefer to multiply the plants in a targeted manner, you can collect the ripe nut fruits (so-called achenes) in fall. On them are the oblong, flattened dark brown seeds. They are ready to harvest when they are dark and very dry. A word of caution: Similar to dandelions, the ripe seeds of cosmos easily fall off when touched. So it's best to have a container underneath to collect them. Since cosmos genetically change with each sowing, the same flower color as in the previous year cannot be guaranteed. Single-variety specimens can only be obtained from retailers. Get amazed!

Seeds of the garden cosmos
Let the seeds ripen on the plant until they are dark in color
Diseases and Pests

In very dry weather, cosmos are prone to powdery mildew. Aphids can appear in summer. Snails like to feast on the fine leaves of young plants. Protect the garden cosmos with snail collars, snail pellets or snail fences during budding. If the cosmos develops a lot of leaves but no flowers, the soil is too rich in nutrients or the plant is not getting enough sun. Then the location should be changed.