Allium Bulbs

Alliums flower from late spring to early summer, bridging the gap between tulips and summer perennials. The bulbs suit sunny perennial borders, gravel gardens and large pots and are popular with bees and bumblebees. They are planted in autumn, from September to November, as long as the ground is not frozen.

Buy alliums: varieties and growth habits

Ornamental onions (Allium) form a large genus with very different heights. Large globe varieties such as 'Goliath' (Allium giganteum) bear football-sized violet flowers on tall stems and make an impact at the back of the border. 'Mount Everest' flowers white, a calm variety for pale planting schemes and as a cut flower. The round-headed leek 'Sphaerocephalon' forms small, egg-shaped, wine-red heads that pop up loosely among grasses and perennials. 'Summer Beauty' flowers later in summer with pinkish-lilac globes and has long-lasting foliage, and 'Forelock' stands out with its two-tone, tufted flower head. If you are looking for the classic 'Globemaster', the large violet globe varieties give a similar effect.

Planting time and position in Switzerland

Plant allium bulbs in autumn; on the Swiss Plateau ideally from mid-September to the end of October, and at higher altitudes a little earlier, before the ground freezes. Alliums need a spot in full sun and free-draining soil. Waterlogging is the most common cause of bulb losses, so a drainage layer of gravel or sand is worthwhile in heavy clay soils. The plants are hardy in Switzerland and survive frosts of minus 15 degrees and more without protection.

Planting and care

As a rule of thumb, plant to a depth of two to three times the bulb diameter, usually about 10 to 15 centimetres. Set small varieties in groups around 10 centimetres apart and large globe varieties 20 to 30 centimetres apart. Water once after planting; after that, natural rainfall is usually enough. The foliage of many species is already yellowing at flowering time; leave it anyway until it has died back so that the bulb can build up strength for next year. The seed heads can be left standing as decoration into autumn.

Combining alliums

Because the foliage becomes unsightly early, alliums are best combined with perennials that hide their base: hardy geraniums, lady's mantle, catmint or salvia. In gravel gardens they go well with grasses and foxtail lilies. Dried flower heads last a long time in a vase. All parts of the plant can irritate skin and eyes and are not suitable for dogs and cats; gloves are sensible when planting. For bees and bumblebees, alliums are a valuable source of food in early summer.