Cosmos: profile, propagation & toxicity

Cosmos features basket-shaped flowerheads that fit perfectly into a cottage garden.

Cosmos (Cosmos) is a summer flower that comes in many different colours. Their numerous delicate and colourful flowers add a summery, cheerful atmosphere to any garden. In addition, the flower offers bees and butterflies plenty of pollen and nectar.

Cosmos: origin and characteristics

Originally from America, Cosmos belongs to the composite family (Asteraceae). The genus Cosmos includes about 48 different species and some varieties that have evolved from them. In our special article we have compiled the most beautiful cosmos species and varieties. Today, the cosmos is widespread all over the world and has established itself as a beautiful summer flower, especially in this country. It and enjoys great popularity across Europe. Cosmos can grow up to 1.50m tall and the double pinnate flowers grow from its long stems. In the species Cosmos bipinnatus, which is common in Europe, Cosmos means beauty and bipinnatus leafy. Its delicate flowers are pink to purple or completely white with a diameter of about 10 cm. There are now even varieties in shades of yellow and orange that belong to the species Cosmos sulphureus. Cosmo flowers not only bring summer flair to the garden, but are also edible and embellish any summer salad.

Tip: cosmos is also a decorative cut flower. The best time to cut is early in the morning. Just make sure the flowers are not yet fully open.

Is cosmos perennial?

Most cosmos species are annuals – only a few are perennials, such as the black and red flowering Cosmos atrosanguineus. These perennial species can form root tubers similar to dahlias and can therefore overwinter.

When does the cosmos flower?

A member of the composite flower family, the ornamental cosmos has its flowering season between July and October. At this time you can see countless colourful flowers on branched stems up to 120cm high among the sparse greenery. The flowering period can be extended by regular pruning.

Tip: cosmos are so-called short-day plants that only come into flower at a certain day length. They need a short period of light and a long period of darkness to flower.

Are cosmos bee friendly?

Although the cosmos is not part of the native flora, the delicate flowers offer plenty of pollen and nectar, especially for bees and butterflies. With its nectar and pollen supply, the Cosmos delights many insects well into autumn.

Is the cosmos hardy?

Cosmos belongs to winter hardiness zone 8 to 11 and is usually not hardy. Originally from tropical areas, ornamental cosmos are very sensitive to low temperatures. Even below 15 °C, they lose their beautiful and edible flowers.

Perennial cosmos can be overwintered by digging up the root tubers in the autumn and storing them frost-free at a temperature of about 5 °C. Potted plants can be cut back before the onset of winter and placed in a frost-free room. The cosmos does not need care in winter, it just must not dry out.

Propagating cosmos

The cosmos can be wonderfully propagated by the self-harvested seeds. The ideal time is in September after flowering. Cosmos seeds are hard to miss – these are narrow, spindle-shaped and dark in colour. Store the newly harvested cosmos seeds in a cool, dry and dark place until sowing in spring. If you do not get around to sowing the seeds in spring, they will keep for between 2 and 3 years if stored correctly.

Tip: when propagating from seed, the flower colour will be a surprise, as they are not varietal. To integrate a specific colour into your garden, we recommend buying appropriate seeds in the shops.

Are cosmos poisonous?

The cosmos is not only non-toxic for humans and animals, it is even edible and can add a refined touch to various dishes, such as salads. This makes the plant perfect for a family garden.