Alliums start flowering in mid-May and, depending on your variety, continue to do so from to the end of July with their lovely, frozen firework flowers.
Alliums have become very "de jour" because their colours range from steely metallic shades to the deepest, velvety purple and because their perfect circular shape defies belief, even probability.
The magic starts even before the flower buds in their papery sheaths - looking like such a mass of potential as slowly a chink of colour is seen and gradually the enormous flower emerges from its impossibly small bud. These fascinating flowers are enormously attractive in both formal and informal settings, acting as full stops in a border or as a striking army when planted in mass ranks. We are sure it is nothing to do with trendy dot paintings, but recently they have kindled the fire of the contemporary gardener more than almost any other plant. Their compact symmetry hits hard against blowsy, frothy plants, and they are not greedy on space or maintenance. In fact, they almost entirely grow themselves; they just need buying and planting well.
Alliums are members of the onion family you will recognise their leaves peeping through the soil very early in the year - just think of the chives in your herb garden - building ballast to put out these stunning flowers. The leaves can be a bit overwhelming because they can swamp smaller plants growing beneath them. They also fade and wilt in an inelegant way, often before the main flowers have appeared. If you are growing alliums in a border where perfection is required then do strip dead leaves away once they die because they will have done their job of stashing sunny resources back into the bulb. Otherwise, grow them among plants that come later and hide all that foliage. Peonies are perfect.
All alliums prefer full sun and a deep, well drained soil that needs some grit if it is heavy to ensure good drainage. If they like their new home, your alliums will become old friends and return every year. If you planted them deeply enough to start with that is. The taller varieties like a little support when young. And all will form clumps if they establish. You will need to divide these once they become too crowded to flower in their own space. Alliums are fecund self-seeders too, so you may need to thin a few to give each their allotted space. Otherwise, plant up the seedlings and grow them on elsewhere. Or, to prevent self-seeding you need to remove the flower heads before the seeds fully form. Give all bulbs a potash feed in spring to encourage their reappearance the following year, especially if your soil is poor. All alliums are fantastic pollen producers attracting bees and bumblebees from far and wide.
They can of course be grown successfully in pots, but you need to make sure that the pots neither dry out EVER or become waterlogged. In pots, it is probably worth sticking to the shorter growing varieties like Allium aflatunense because they are less likely to collapse on you. Plant them 10-15 cm deep in your pot to try to avoid collapse but bear in mind that all bulbs need at least 5 cm of compost beneath them to do well.
The best known member of the family has to be Allium hollandicum Purple Sensation with its deep violet-purple afro flower that is soft to the touch and lasts for ages. It is also a serious height - 90cm on average - is one of the first on the allium scene and the most tolerant of shade. Awarded the RHS AGM for its attractive seedheads, you need to cherish the flowers even after the colour has leached away. Dry them and spray them with gold for jollying along an autumnal or Christmas arrangement. It was Purple Sensation that was used to such striking effect in Rosemary Verey's laburnum walk at Barnsley House - now a garden classic combo and not dated in any way.
Allium christophii amaze in June (usually and depending on the weather). Being native to Iran and Turkey they like it hot and maybe consequently their floral sphere is lighter and more airy than most with a pale green central bullseye to each metallic star flower. What it lacks in height (60 cm) it makes up for in breadth: its flowers can reach up to 50 cm in diameter. More tolerant of heavier soils than its brethren, Christophii will still multiply and return if there is adequate drainage.
Allium hollandicum Aflatunense is much muddled with its cousin Purple Sensation but in fact it is shorter growing, and quite a different, paler more lilacy colour. Its powder puff of a flower combines well with any of the other alliums and its lilac colouring is softened by the silver halo effect it casts around it. It is as reliable as Purple Sensation but the flowers within the globe are not quite so tightly packed.
Allium nigrum is in fact creamy white and like Purple Sensation is one of the tallest alliums. Its wide grey green leaves will die back as the slightly flattened flower emerges in early June. Each flower comprises many mini-flowers around a prominent pale green ovary. Allium nigrum has been grown since 1762 and is the allium to grow and survive to multiply in rough grass. Then it takes over the floral mantle from Narcissus Cheerfulness, Spring Green tulips and then Camassias and which also all do well in unmown grass before the alliums arrive.
Nectaroscordum allium is known romantically as Sicilian and less romantically as Garlic. The epithet Mediterranean Bells really suits it because the flower is a random scattering of deep pink and green bells that dangle downwards like a parachute. Its effect is more allium-like than pure allium but it does well in shade which is odd considering its Mediterranean roots. Plant it en masse otherwise its subtle colours can fade into the background.
While not NEEDING much around them, alliums do look marvellous with the greens of Alchemilla mollis or Lady's mantle to disguise the allium leaves and to show off the shape and colour of the flowers. Hardy perennial geraniums like Roseanne or are another choice and the later alliums contrast with startlingly good effect with peonies too. The fairy tale colours of honeywort or Cerinthe major purpurascens would be another perfect partner.
If you were to wander round your garden now, you could spot the places that lack this superb and easy to grow addition to your garden. Mark them with a stick and put your order in for all your spring flowering bulbs soon. Planting should take place in autumn, along with your daffs, but there is nothing wrong with planning ahead because that is what gardening is all about, a constant readjustment and improvement year on year on what has gone before.