Allium Luna

Allium Luna puts everything into one rounded head of small starry flowers, held clear on a single bare stem. That head sits above strappy basal leaves which fade as the flower opens, which is the plant's one design problem and the key to placing it. The head does not stop working when the colour goes: it dries in place to a sculptural seed head that holds its shape for months. It is grown in borders, repeated through mass plantings, and cut for the vase.

Sun, sharp drainage and the summer rest

Alliums are onion relatives and they want what onions want. Full sun is not negotiable, and water needs sit low to moderate: enough through the growing and flowering period, then much less once the leaves begin to fade. Drainage matters more than soil richness, so work coarse sand or gravel through heavy ground, or raise the bed. Plant in groups of five or more rather than singly, spaced so each head has clear air around it, and site them behind low perennials or a fine grass so the fading foliage is hidden. Growth is moderate, so a clump takes a season or two to look furnished. The failure mode is simple and it catches east coast gardeners every year: a wet, humid summer over dormant bulbs rots them in the ground. If your summer rain is heavy and your soil is heavy too, grow them in a raised bed or a deep pot of gritty mix where you control what the bulbs are sitting in. Lift and divide only when a clump stops flowering freely, and replant straight away into fresh gritty soil.

Allium against the tufted natives

Two other clump formers here look similar on a plan and behave nothing like it. Morning iris holds a tidy evergreen fan of leaves all year and flowers blue in short daily bursts through spring, so it earns its space out of flower as well as in it. Spear grass is pure texture, a tight native tussock for banks and revegetation. Allium Luna is the one to choose if you want a cut flower and a seed head you can leave standing into autumn, and the one to avoid if you need that patch of bed to look furnished at ground level all year. Where there is room for only one clump former in a hot, freely drained bed, the morning iris is the lower risk buy.

Deadheading, or not, and what to feed

Resist deadheading. Leave the spent heads standing so they dry on the stem, and cut them only when they finally break down or when you want them indoors. Let the basal leaves yellow off naturally rather than tidying them away, because that is when the bulb is putting away next season's flower. Feed as growth starts in late winter with a fertiliser high in potash and low in nitrogen, since soft nitrogen driven growth gives you leaf, floppy stems and fewer heads. Nothing more is needed once flowering finishes, and the bulbs prefer to be left dry and undisturbed until they come away again. One caution if you are cutting stems for the house: like every onion relative, the bulbs and foliage are toxic to dogs and cats, so keep cut stems and trimmings where a curious animal cannot reach them.

Choosing a size

This plant is supplied in one size, 140mm, at $16.95 per plant. The size shown is the pot it arrives in, which is the rootball, not the height of the plant. Not sure which to choose? Read our guide to when to plant in Australia.