The Casual Gardener: Know your ornamental onions

Your borders may be brimming but alliums still tower head and shoulders above the rest

If it’s wow factor you’re after, it’s hard to go past Allium 'Globemaster'

WE HAVE lift off. As mid-summer fast approaches, the ornamental garden has responded accordingly – the billowing foliage of the cranesbill geraniums topped by pink and mauve flowers, bees buzzing around the bright yellow emerging blooms of the Anthemis, while the papery, red oriental poppies burst from buds resembling furry alien eggs.

Punctuating my busy borders are the alliums, their pompom flowers suspended on thin stalks, creating an illusion of floating purple spheres.

Also known as ornamental onions, the family connection to one of our favourite cooking ingredients isn't immediately apparent. However, if you've ever allowed a leek to reach full maturity, the relationship is obvious. Leave it over winter to fatten up and by spring the top of its stalk will bulge with the beginnings of a flower concealed inside. It'll be late spring or early summer by the time the flower finally reveals itself – a tennis ball-size grey-coloured orb.

Not as attractive as one of its ornamental counterparts but the bees love them nonetheless – and they're a great plant for drying.

The colour lacking in the flowers of the leek can be found in its smaller cousin, the chive – a plant I believe is deserving of more culinary and horticultural limelight. Simple to raise from seed, chives best represent the onion family's ability to perpetuate itself. Plant a handful in the spring and by summer you'll have a clump, ready for harvesting and ideal for dividing later in the year.

The chives' purple flowers will also bring colour to the vegetable garden or to a terracotta pot close to the back door or window sill – anywhere near to the kitchen.

But in June it is the much larger alliums that are stealing the show with their globed clusters of tiny flowers grouped closely, yet orderly. It's a short-lived display relative to a cranesbill geranium or the ornamental grasses that provide perfect underplanting. No sooner have the flowers of the allium succeeded in creating a symmetrical sphere than they start to go over, turning green but thankfully maintaining their shape.

The comparative brevity of the colour is a minor quibble, though, as alliums are among the most effective architectural plants and generally great value year after year.

If it's wow factor you're after, it's hard to go past A. ‘Globemaster'. Reaching more than four feet in height, they boast deep violet flowerheads, spanning up to six inches across. Such class does not come cheap, however, and you can expect to pay as much as £5 a bulb when buying in September.

A cheaper option is the smaller and only slightly less impressive A. 'Purple Sensation'. Notably, you'll get around 10 bulbs for the price of one ‘Globemaster' and they are widely available.

At around three feet in height, ‘Purple Sensation' still towers above most of its contemporaries in the border, while the dead seed heads will endure throughout the summer.

A ‘Christophii' – AKA ‘star of Persia' – a plant whose delicate appearance belies a more robust plant is another excellent that dries nicely. Plant all the above in informal groups of odd numbers – three, five or seven, avoiding linear or rigid patterns.

Position in a well-drained sunny border among other herbaceous plants. The other plants will help to mask the alliums' strap-like leaves, which fade by the time the flowers appear in late May and early June.

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