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An array of cosmos, with bright pink and white flowers.
Do you dream of creating a romantic wildflower garden? Cosmos will help make that dream a reality. There’s nothing like the sight of these beautiful, daisy-like blooms swaying in the breeze on their slender stems. And the good news is that cosmos is simple to grow and makes an exquisite cut flower, too.

 

What you need to know about cosmos

Name: cosmos, garden cosmos, Mexican aster, Cosmos bipinnatus, sulfur cosmos (Cosmos sulphureus).

Height: 20cm-120cm.

Plant type: mostly annual.

Climate: warm and cool temperate, subtropical, tropical and arid.

Soil: moist, well-drained soil enriched with compost.

Position: full sun.

Foliage: lime green or grey green, finely divided, fern-like.

Flowers: masses of daisy-like or cup-shaped blooms appear from summer to autumn in vibrant and soft shades of white, pink, carmine, red, yellow, and orange. Hybrids may be bicoloured with single, semi-double or double flowers with entire or fused petals.

Feeding: liquid feed regularly with a fertiliser that’s specially formulated for flowering plants.

Watering: water regularly.

Appearance and characteristics of cosmos

Cosmos is the quintessential cottage garden flower. It produces masses of charming, daisy-like, or cup-shaped blooms on slender, upright stems. The foliage is airy and fern-like, adding to its wildflower appeal. Traditionally, it grows to 100-120cm tall, but shorter forms are available.

Cosmos varieties feature a wide range of flower shapes and colours. The species form has a single bloom, but hybrids may have single, semi-double or double flowers with entire or fused petals. They can also be bicoloured.

Close up of a cosmos, a bright pink flower with curved petals.

Is cosmos edible?

The young leaves and flowers of Cosmos sulphureus are edible, provided they have been organically grown. Other cosmos flowers are not considered edible – while they’re not toxic, the taste is not pleasant.

Uses for cosmos

Cosmos is a magnet for pollinators, so is an ideal choice if you’re looking to encourage bees and butterflies into the garden. Mass plant cosmos in garden beds, along borders, or in pots for a dramatic display. Cut flowers regularly and arrange in vases or bouquets.

How to grow cosmos

In most climates, you can sow cosmos seed in spring (once the chance of frost has passed) and in early summer. Sow in trays if soil is still cold or directly into garden beds enriched with compost, lightly cover with soil, and keep moist. Germination can take seven to 21 days. Thin out seedlings, allowing 30-50cm between plants, depending on their expected eventual height. Once seedlings have formed three pairs of leaves, pinch out the growing tip to encourage bushy plants that will produce more flowers. Staking is required for tall plants, (greater than 60cm) especially in windy locations – use thin stakes and garden twine.

Caring for cosmos

Deadhead the spent blooms regularly to promote new buds. Plants will often continue to flower well into autumn or until the first frost. To deadhead, cut the stem just above the foliage.

A field of yellow cosmos flowers in bloom.

How often should you water and feed cosmos?

Keep plants well-watered as they grow, especially during dry conditions. Spread a layer of organic mulch over the soil to help conserve moisture.

Liquid feed fortnightly with a fertiliser that’s specially formulated for flowering plants.

When do cosmos flower?

Cosmos usually takes 10 to 14 weeks from seed to flower. To harvest cut flowers, pick when the petals are starting to open but not fully flattened. Place in a vase and change water daily.

Diseases and pests that affect cosmos

Slugs and snails love tender young seedlings. Use physical barriers or slug and snail bait to help keep them away. Aphids and spider mites are also common pests and can be controlled with organic sprays.

How to propagate cosmos

Species cosmos will readily self-seed and flower the following year. Hybrids may seed, but they’re unlikely to produce the same desirable traits as their parent plants.

If you like this then try

Billy buttons: a cute perennial with pompom yellow flowers on tall, slender stems.

Cuphea: this hardy groundcover is covered with tiny white or pink-purple blooms throughout the year.

Angelonia: a floriferous annual or perennial with spikes of purple, red, pink, blue or white flowers.

Start planting today

Check out our huge range of flowering plants now and get your garden growing!

 

Photo credit: Getty Images

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