When you want vivid garden colour without a lot of fuss, look no further than cosmos – not the stars in the sky but the colourful flower. Here are some interesting facts and tips to help you grow your own.
Facts about cosmos
Cosmos are native to Mexico and are well suited to lean soils and fluctuating weather.
- These plants have the airy look of a wildflower, standing 0.6 to 1.2 metres (two to four feet) tall.
- They produce a bevy of white, pink, red, yellow or orange daisy-shaped flowers, each with a yellow centre.
- Below the flowers, the leaves are lacy and finely cut, making them a perfect accent for blossoms that linger for weeks.
You can intersperse tall varieties with other tall annuals or perennials in beds, or grow mid-sized cosmos in containers or in gaps in beds where you need a quick flower to fill in empty space.
- Some of the tall varieties may need staking, or you can grow them in close company with stiff, upright flowers such as cleome or tall zinnias, whose stems will keep the cosmos propped up.
- Compact and dwarf varieties require almost no maintenance beyond clipping off spent blossoms.
Choosing your favourite
The most popular cosmos is Cosmos bipinnatus, often called garden cosmos. This species adapts to cool weather, so it’s perfect for our climate, and blooms in white, red and many shades of pink. Some other popular varieties of cosmos include:
- The 0.6-metre-tall (two-foot-tall) Sonata multi-coloured mix, which is tremendously versatile.
- ‘Candy Stripes’ which is a taller variety of cosmos, with white flowers edged in crimson.
- Seashells mix has unique rolled petals, also in a range of light pink to red shades.
- C. sulphureus, often called sulphur cosmos, is a different looking species of cosmos that blooms in bright yellow, orange, red and bicolours.
- The varieties ‘Bright Lights’, ‘Cosmic Orange’ and ‘Lemon Twist’ have a better appetite for hot weather than garden cosmos do.
Boosting the yield
To boost the yield of cosmos in your backyard, simply mix the contents of a packet of seeds with an equal amount of sand. Then, broadcast by hand to grow cosmos as a “wildflower” in your garden.
- Scoop up handfuls of the mixture and toss it with a broad, sweeping gesture onto cultivated, weed-free soil.
- Garden cosmos will germinate in cool soil, so you can sow seeds around the time of your last spring frost.
- Sulphur cosmos is slightly more tender and should be started indoors about six weeks before the last frost date.
- If you are concerned about root damage, transplant the seedlings into individual peat pots to minimize damage at planting time.
Of course, you can start growing cosmos whenever you’d like if you plant seeds in containers. Cosmos take to container life easily and readily produce their signature dainty, colourful blossoms.
Cosmos is a flower that will survive conditions that would kill many other plants.
- Cosmos benefit from soil that is loamy and deeply dug, but they need little, if any, fertilizer, even in poor soil.
- Dry conditions promote strong growth and too much moisture can lead to root and stem rot.
- It is wise to rotate cosmos by planting them in a different location every year to prevent disease.
- If you find chewed flowers, hand-pick beetles in the morning when they are sluggish or spray an insecticide labelled for cosmos containing the botanical insecticide pyrethrum.
Even a small garden patch devoted to cosmos is a beautiful sight, especially when courted by butterflies.