No garden should be without cosmos and its heavenly flowers. After a bit of a slow start with these brightly-coloured blooms, I’ve become a convert, and now I sow them from seed every year to ensure I’ve got plenty of these cheery favourites to brighten up my borders.
Cosmos bipinnatus are half-hardy annuals, which means, like bedding plants, they will grow and flower within one season, and can then be composted when they’re spent in the autumn. Their large, daisy-like flowers are most often seen in shades of pink or pure white, but they can also be found in ‘hot’ red and orange – there’s even a relatively new yellow variety. They are very easy to grow and you can easily buy them as young plants – but you’ll get much more for your money if you sow them from seed any time between March and May. Simply sprinkle onto a tray of moist compost and cover lightly. They’ll benefit from bottom heat, but will also germinate fairly readily if covered with a plastic bag or clear lid and left in a greenhouse or sunny windowsill.
Once their second pair of leaves is showing (the ‘true’ leaves) they can be pricked out into bigger pots and grown on until they’re ready to plant out after the last frosts. Pinching them out (removing the growing tip) makes for bigger and bushier plants with more flowers so this is well worth doing at this point or when they’re about a foot or so tall. Once they’re in the ground and flowering it’s a good idea to deadhead them regularly as removing the spent flowers makes room for more to bloom – and bloom they will! These generous plants will flower non-stop from midsummer until the first frosts, perhaps even later. With last year’s mild autumn, it took a real dip in the temperatures to kill off my cosmos, so I was able to enjoy them well into November.
There’s quite a wide variety of cosmos to choose from, but all are reliable performers so choosing is simply a matter of taste. For a pure hit of colour you can’t go wrong with ‘Sensation’ – a mix of light and dark pinks with some white flowers and well worth growing. There’s also ‘Dazzler’ with large deep red flowers, or ‘Versailles Tetra’, which are slate-pink with a red centre surrounding the bright yellow eye of the bloom. Last year I was quite taken with ‘Daydream’, which is a bit more delicate looking – very pale pink, deepening in colour towards the centre of each petal. However my firm favourite is ‘Purity’, These are quite a tall variety, so best towards the back of a border, with large, brilliant white flowers. They look fantastic with other cottage-garden style plants or in a vase, providing light and texture with their feathery foliage and stunning white blooms.
Cosmos aren’t just for the garden – dwarf varieties are great in pots – try ‘Sonata’ or ‘Apollo’, which are more compact and will suit container planting. For something a bit different, go for ‘Xanthos’ which flowers prolifically and is the first yellow cosmos in a really pretty, soft shade. There are other more unusual varieties of cosmos which come in all shapes and sizes – ‘Cupcake’ is so-called because its fused and upturned petals look, well, like a cupcake! Or there’s ‘Sea Shells’, which has tubular petals, and ‘Double Click’, with a lovely ruffled, fully double flower, in a range of colours from cranberry through to rose.
Cosmos are easy to grow, flower for ages and are great for filling gaps in borders, or as a temporary fix for an empty flower bed – they can even be planted alongside vegetables, to help bring in those useful pollinators, and they’re a stalwart of the cut flower patch too. They’re great dotted around the garden or in a vast swathe of airy, feathery foliage dotted with those brilliant blooms. Cosmos are cosmic for every garden – so get growing!
Chocolate cosmos
Chocolate cosmos is another member of the cosmos family, but not exactly like the others. Why is it called chocolate cosmos? Well, partly because of its rich, dark, red/brown colouring but also because of its scent – if you get up close to the flower you’ll smell its wonderful vanilla-chocolate aroma. Also known as Cosmos astrosanguineus, this plant is perennial, and if you look after its slim tubers (by lifting or covering during the winter) then it will return year after year. It’s not as common as its bright and beautiful cousins, but it’s got a velvety, sultry charm which is hard to resist. These are most often bought as young plants, as seeds are hard to come by and can be tricky to germinate. Chocolate cosmos are much smaller than Cosmos bipinnnatus, with loose, slender stems. I plant mine in a large container with grasses to give some contrast and also to help support the flowers…after all, I want them as close to my nose as possible for that fantastic hit of chocolate!
This article was originally published in The Courier’s Beautiful Homes supplement, Spring 2019
Julianne Robertson 
Well done!
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