Cosmos is a lovely non-toxic flower

Rate this item
(1 Vote)

Sonata Mix Cosmos. Picture courtesy Ball Horticultural CompanySonata Mix Cosmos. Picture courtesy Ball Horticultural CompanyCosmos is a lovely non-toxic flower which is recommended for children’s gardens and safe around cats and dogs.

Cosmos are beautiful summer flowering annuals native to Mexico, where most of the species occur, as well as the United States, as far north as the Olympic Peninsula in Washington; and Central and South America, as far south as Paraguay.

One species, the commonly called “Mexican Aster” (Cosmos bipinnatus) escaped gardens and naturalized itself across much of the eastern United States and eastern Canada, growing abundantly on disturbed land besides roads, and in fields and waste areas. It is also widespread over the high eastern plains of South Africa, where it was introduced via contaminated horse feed imported from Argentina during the Anglo-Boer War. In South Africa they flower religiously around Easter time, transforming open fields and roadways with their masses of flowers, and the flowering can continue until the first frosts.


Spanish priests grew cosmos in their mission gardens in Mexico, and it was their perfect, evenly placed petals which led them to christen the flower "Cosmos," the Greek word for harmony or ordered universe. Although there are 20 known species of cosmos, two annual species, the commonly called Yellow Cosmos (Cosmos sulphurous) and the Mexican cosmos (Cosmos bipinnatus) are most familiar to home gardeners, and easy to tell apart.

The Mexican cosmos is a tall, bushy annual growing between 1 and 2m high, with very finely divided mid-green leaves, and large pink or white flowers with a central disc of tightly clustered, usually yellow, inner disc florets. Plant breeders have been hard at work, and today this cosmos comes in many named selections which include single, semi-double or fully double blooms in a variety of awesome colours ranging from lilac to deep carmine, scarlet red, and even Cosmos 'Antiquity' Picture courtesy Ball StraathofCosmos 'Antiquity' Picture courtesy Ball Straathofpeachy-pink and pale yellow. These new hybrids flower very profusely and for much longer, and exciting new dwarf varieties are also available which are extremely compact, and because they only grow 30 to 50cm tall, are suitable for even the smallest gardens and grow beautifully in pots - even if you only have a sunny balcony, you can grow at least one!

Cosmos bipinnatus 'Antiquity' is a good example of a new and beautiful dwarf variety of cosmos with rich burgundy coloured flowers that change to antique bronze and salmon with age. This little gem may only grow about 38cm tall, but makes up for its lack in stature with its masses of flowers.  It is also a tough garden performer that tolerates poor soil, heat and humidity.

Cosmos sulphureus 'Bright Lights' is also known as Sulphur Cosmos and Yellow Cosmos. It is freely available and remains popular, not only for its ease of growth, but also for its lacy foliage and profusion of brilliant flowers in shades of orange, yellow, and flame-red, blooming from early summer until the first frosts. It loves full sun, tolerates humidity and grows quickly to a height of 90cm, and like other cosmos, thrives on poor soils.

 Sonata Carmine Cosmos. Picture courtesy Ball Horticultural Company Sonata Carmine Cosmos. Picture courtesy Ball Horticultural CompanyIn the Garden:

Because cosmos is non-toxic and so easy to grow, it is recommended for children’s gardens. It is also safe around dogs and cats.

Modern cosmos hybrids are compact, easy-to-grow and very free-flowering. They also last well in a vase, and the more you pick them, the more they will bloom, attracting butterflies, bees and other beneficial insect pollinators to the garden.

The taller varieties make a wonderful background plant for the flower garden and are marvellous in wild meadow and cottage gardens. Dwarf strains are perfectly charming if planted as borders and thrive in containers, making them perfect for brightening up patios, balconies and courtyard gardens.

Modern cosmos hybrids are compact, easy to grow and very free-flowering, but to flower well they require full sun and moderately fertile soil which drains well - if the soil is too rich and fertile they will not perform as well. This makes them ideal to grow in many of the drier summer rainfall regions of the country where the soils are less than perfect. In the winter rainfall regions, they will require regular summer watering, and in very humid regions they are susceptible to fungal diseases, although newer hybrids will tolerate more humidity.

Potted plants and seedling trays are available from garden centres, which can be planted out at any time, making them very handy for small gardens and containers, but gardeners on a budget prefer to sow the seeds directly where they are to grow, in late spring. Germination should take place within 4 to 7 days in ideal soil temperatures between 18 and 21°C. Lightly cover the seeds with soil, and thin out the small seedlings to space them correctly - check the plant label or seed packet. Cosmos grows quickly, and modern hybrids can start blooming within 10 to 12 weeks after sowing, but in some climates, cosmos sown in spring may not come into full bloom until the days become shorter in late summer.
Sonata Pink Cosmos. Picture courtesy Ball Horticultural CompanySonata Pink Cosmos. Picture courtesy Ball Horticultural CompanyBesides moderate watering during dry spells cosmos will need no further attention or feeding, besides keeping the beds free of weeds. Cutting flowers for the vase, and deadheading spent flowers regularly will prolong flowering, but at the end of the season leave a few seed heads to ripen and self-seed, or collect and store for next season.

Problems, Pests & Diseases:

If grown correctly cosmos suffer from no serious insect or disease problems, but may occasionally be attacked by aphids or red spider mites, which can be treated with insecticide soaps or other appropriate insecticides.

During moist, warm weather, and in humid regions, they can be susceptible to powdery mildew and other fungal diseases.