Cosmos are bright, open-faced flowers that attract bees, butterflies and beneficial predatory insects into the garden. Colours range from yellow and orange to white, pink, purple and a rich deep chocolate. As well as brightening up the garden they make good cut flowers for decoration indoors. Cosmos are annual plants that flower, set seed and die all in one season. Depending upon variety you can get them growing from just below knee height to shoulder height on the average adult. Cosmos are particularly handy for the vegetable garden as they have slender stems and ferny foliage that does not overpower plants close by. They can be popped randomly around beds or planted in groups for more visual effect.
Companions Plant with dahlias, cleome, echinacea. sun flowers.
Sow or plant in early spring and summer countrywide.
Cosmos grows well in full sun as well as partial shade. They can easily be planted between rows and in amongst your vegetables.
Cosmos will grow well in most garden soils. They do prefer a reasonably rich, most soil that has adequate drainage and does not get too water-logged. If your soil is sticky then dig in coarse sand or fine pumice to help improve drainage.
In early spring, sow seeds a finger-tip deep in trays or punnets filled with seed compost or directly into the garden. If sowing directly into the garden thin seedlings so that plants end up with around a hand’s length between them.
When your seedlings are about a finger’s length in height pinch out the tips to encourage strong, bushy plants as opposed to lanky leaning specimens. When the weather has settled and is reliably warm and sunny, plant seedlings at an average spacing of a hand’s length apart. I usually dot them around the vegetable garden on the fringes.
Water young seedlings in dry periods. Once they are established and starting to grow you shouldn’t need to continue with watering unless weather is persistently dry and young plants show signs of wilting. If plants grow well they may need staking for support in windy areas.
Flowers can be cut for use indoors. To keep plants going, once the first flush of flowers has passed, cut away the top third to stimulate production of more flower buds. Taller growing varieties may need staking or planting between and behind tall plants – such as runner beans, sunflowers, cleome – for support.
As an annual, cosmos will die at the onset of winter. Allowing cosmos to flower and self-seed means you’ll be rewarded with a range of plants in all sorts of unexpected places next spring and summer. When you spot small seedlings in the spring you can simply lift them with soil around their roots and re-position them where you want them. Alternatively, pick off the clusters of elongated seeds before they start to fall and store in a dry place until next spring when you can sow where you want them.