Alliums, or ornamental onions, are hugely popular in gardens throughout Europe. They have been in fashion for years, and with good reason. Alliums bring exuberance to the garden with their fun baubles of colour at a time when the summer garden has not yet reached its peak. They are extremely easy to grow, and their flowers come in a great range of colours, from purple, pink and blue to yellow and white. Plant sizes within the family vary considerably, with tiny species available for rock gardens to the drumstick types with stout upright stems topped with balls of colour.
Native to most of the Northern hemisphere, they are distributed throughout a great number of countries and regions around the world and include the ornamental bulbs as well as many indispensable edible types such as onion, garlic, chives and leeks.
Alliums create excitement in a flower bed and can be planted in many different ways to optimise their impact on a garden. They look fabulous in groups, and can be interplanted with lush foliage plants in a wave that will lead the eye around the garden.
Dot the bulbs among other perennials and forget all about them until early summer when you rediscover where you put them and are rewarded with beautiful nodding firework globes.
The taller family members provide vertical interest and rounded symmetry to mixed areas of planting where other varieties are grown for their massive pompom-like flower heads that are almost the size of melons. If you do decide to buy some bulbs, look for the heaviest and largest ones for the best flowers, and as with other bulbs, plant them at a depth three to four times the diameter of the bulb.
Allium giganteum produces flower balls the size of grapefruits
They are widely available as young plants for immediate effect, but this will be more expensive, so plant bulbs from late September to November. Their root systems will develop over winter and they will flower the following year.
In the wild, Alliums often grow in poor, stony ground and thin soil, so you don’t need to enrich your soil. On the whole, they will thrive in well-drained soils in a sunny position and look glorious in any garden. Whether you prefer a relaxed cottage-garden style or more formal and co-ordinated planting, there will be an Allium to suit you. The single-flowering stem of each bulb lasts for weeks, and their seed heads have added value as they can be dried and used for decoration, or when left in situ look great in the border on a cold and frosty morning. Alliums bring fireworks in the summer and still contribute much appreciated structure to the border throughout winter.
Allium giganteum
This Allium is one of the tallest at 1.2m. It flowers from June and produces flower balls the size of grapefruits that are made up of tiny, purple, star-shaped flowers. As with most of the family, it is best positioned among heavy foliage as its strap leaves die away at flowering time and will need some camouflage.
Allium cristophii
The melon-sized flower of this species has a deep metallic purple colour and sits on strong, thick stems with quite strong foliage. It is fantastic in the border as it is a fast-spreading variety, and reaching a height of 60cm means that it is great right at the front.
Allium x hollandicum ‘Purple Sensation’
Fantastically dependable, this Allium has rich, deep plum flower heads with a 10cm diameter. It is an excellent combination plant. Try planting it with grasses or box for great effect.
Allium ‘Globemaster’
The Globemaster is a good tidy plant with sturdy stems and leaves that persist. It bears one of the largest and densest purple orbs at 20cm and will present you with a second flush of flowers as the first ones fade, extending their effect.
Allium ‘Mount Everest’
Another grapefruit-sized globe, but this time made up of a mass of white flowers on a strong stem. It towers at 1.2m and will complement brightly coloured planting beautifully.
Plant of the week
Sorbus aria Lutescens Whitebeam One of my favourite sights of spring is this Sorbus as its leaves start to unfurl. Tightly pleated, they unfold in accordion fashion to reveal grey-white foliage with white undersides. The overall effect is of a delicate mint ice-cream hue that is quite eye-catching amongst the emerald greens of other fresh spring growth. A small-to-medium deciduous tree, it’s a good choice for a windswept or seaside garden, chalky soils, and is also planted as a street tree due to its tolerance of pollution.
Reader Q&A
My camellia this year is covered in a sooty black substance. What can I do about this? M Roche
This sooty substance is black mould or fungus. It is caused by aphids or scale insects on your plant excreting honeydew, which forms the perfect base for this sooty mould to grow. You can remove this and the offending insects by carefully washing the plant with a soapy water mix. Watch out for returning aphids — check the underside of leaves as well for pests — and keep removing.
Submit your gardening questions to Diarmuid via his Instagram @diarmuidgavin using the hashtag #weekendgarden
