This summer I went all in with Allium giganteum, and what a show it was! Last years bulbs returned, and the ones I planted in autumn completed the border. This border is only on its third year, so in the beginning of June it still has gaps in the planting. (Yet what are gaps except an opportunity to fill it up with more spring bulbs next autumn!) The giant onions are originally from central and southwestern Asia, but have been cultivated in many countries and are widely used in borders.
Once again I have gone for a simple colour scheme of pale pink through to mauve, purple and blue. I tend to fill my borders with favourite plants such as columbines (Aquilegia vulgaris), Armenian geranium (Geranium psilostemon) and Johnsons blue (Geranium x johnsonii), Lady's mantle (Alchemilla mollis), Great Burnett (Sanguisorba officials) and Catnip (Nepeta × faassenii) which all flower around the same time. Later in the season the border changes, with more blue, yellow and orange elements added to the scheme.
The giant onion bulbs are planted in autumn in free-draining soil in a sunny location. They are draught tolerant and don't need much feeding, but the bulbs are easily damaged so it is best to grow them in a place where they are not disturbed. That said, once the leaves have died down you can lift them without problem if they need dividing. Like most bulbs, they dislike waterlogged soil or exposed locations. I lost quite a few alliums from last year in an other border where it evidently was too wet, so that is a misstake I won't make again. Otherwise they are very easy plants to grow, and given the right conditions they put on a great show and survive the cold winters quite happily. Because the leaves are quite large they can become unsightly after the flowering period, and therefore it is great to hide them amongst leafy perennials.
On a hot summer we water the surrounding perennials but not so much the alliums, as they prefer dryer rather than soggy conditions. The globes consist of lots of tiny flowers and once the flowering is over the seed-heads are a decorative element in themselves so I usually leave them standing until autumn. This also means that I can see where they are located and I avoid disturbing the bulbs as I fill up any gaps with more spring bulbs around them. Bees and butterflies love the nectar rich flowers and as they last for many weeks it is a great plant for the environmentally concerned gardener to grow!
