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Cosmos, colors and light: planting, care and blooming

cosmos flower

Cosmos is a very cute little annual plant, very trendy nowadays.

Key Cosmos facts:

Name – Cosmos
Family – Asteraceae
Type – annual

Height – 8 inches (20 cm) to 5 feet (1.5 meters) depending on the variety
Exposure – full sun

Soil: ordinary, rather light and well drained  –  Flowering: end of spring → mid-fall

A very easy plant to succeed in growing, the blooming is abundant and its decorative effect is guaranteed.

Sowing Cosmos

In spring, right from the middle of the month of April, choose a full sun location to sow your cosmos.

If you live in areas that are farther up North, best sow starting from the month of May.

cosmos plantingIn summer, it is always possible to plant your cosmos plants purchased in a nursery pot, but the most common technique is to sow them directly from seed.

  • After having sown the seeds, water regularly to ensure that the soil remains damp.
  • Once seedlings have sprouted well, you may thin them to give breathing space to your young plants. This means removing those sprouts which are too weak and too crowded together.

Just like the aster, ordinary soil mixed with a bit of soil mix is perfect.

  • Avoid compact and heavy soils that would retain water instead of releasing it to the plant.
  • To nicely cover a surface, plant around 8 or 9 flowers to a square yard (1 m²).

Care and pruning of cosmos

Caring for cosmos flowersEasy to grow, cosmos only asks for very little care.

For long stemmed varieties, feel free to stake them to avoid having them double over in case of wind.

Deadheading will help renew blooms. It also makes the flowers seem perpetually fresh!

  • Note: if you want seeds, let a few flowers mature and dry out.

All there is to know about cosmos

A plant for flower beds, edges or rocky land, cosmos is spectacular from spring to fall thanks to its generous blooming which constantly renews itself.

An easy annual, there are many different varieties and species which makes for just as many shapes and colors.

As for pests and diseases, Cosmos is rather something of a paradox:

  • It attracts aphids away from other plants, thus protecting them. This makes it easier to use as a decoy to eradicate early aphid colonies.
  • Conversely, it repels certain butterfly pests, like large white, from laying eggs in the area. But it still shares its nectar to them willingly.

Common varieties of cosmos

Cosmos varietiesThese can be divided into three large groups, for the most common flowers

  • Cosmos bipinnatus – the most common one, with white, pink or red flowers.
  • Cosmos sulphureus – the hues from these vary from yellow to orange.
  • and finally, Cosmos caudatus – a more wispy variety native to South America

Not a very hardy plant, cosmos cannot withstand temperatures below freezing. This goes for all varieties. It explains why it must be grown as an annual in cold climates.

  • In warm climates, cosmos will grow to a bushy 4 feet tall (1.30 m), and has a lifespan of about 8 months.

Cosmos, beautiful edible flowers

From the three groups mentioned above, only two are traditionally regarded as edible: Cosmos sulphureus and Cosmos caudatus.

  • Pick young leaves and flowers and add them to chop suey.
  • Sprinkle a few petals to decorate a colorful salad bowl!

The most common Cosmos family, Cosmos bipinnatus, is not considered edible. Since it isn’t toxic in any manner though, it’s still very safe to grow around children and pets.

Smart tip about cosmos

Cosmos is one of the favorite flowers of bees and other beneficial insects.

Images: Pixabay: Annca, Ilona, Hartono Subagio, Sonja Kalee
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  • gina wrote on 4 August 2021 at 17 h 01 min

    Leave some of the flowers that have gone to seed on the plant to attract birds who land on the plant and eat the seeds directly from the withering flowers! Don’t deadhead all the flowers.

  • suvro wrote on 26 March 2019 at 15 h 37 min

    I just love Cosmos! They grew so well in California… just add water. I figured Houston, TX, with it’s tropical climate might not work. But I’m gonna give them a try.

    And edible? After all these years loving this flower, I didn’t know it was edible either. Definitely gonna get some going in the Spring, here… Around the middle of January… LOL.

    • Gaspard Lorthiois wrote on 26 March 2019 at 20 h 11 min

      It’s true that Cosmos is edible! Petals are best. Not really tasty but beautiful to top a fresh salad mix! A word of caution, however: the most common type of cosmos isn’t really edible. It’s the other two, Cosmos sulphureus and Cosmos caudatus that can be eaten when young.