Purple-blue florets bunch into balls 8 to 12 inches across, held on stalks that can top three feet: this is giant onion (Allium giganteum), an ornamental relative of garlic, onion and chives, grown for flower beds, pots and bouquets. Give it full sun and light soil that drains well — even poor ground will do — and the display is guaranteed.
| Name | Allium giganteum |
|---|---|
| Family | Liliaceae (lily family) |
| Type | perennial |
| Height | 8 to 40 inches (20 to 100 cm) |
| Exposure | full sun |
| Soil | ordinary |
| Flowering | late spring to midsummer |
Easy to grow, it is perfect in flower beds and also in pots or garden boxes to decorate either a terrace or a balcony.
Giant onion is planted in fall more or less 4 to 5 inches (10 to 12 cm) deep in light soil.
A good way to know how deep to plant it is to multiply the height of the bulb by 3. If it is 2 inches (5 cm) tall, plant at a depth of 6 inches (15 cm).
Caring for giant onion is extremely easy, since the needs of this perennial bulb plant are not complicated.
In both pots and in the ground, they will bear nice flowers without asking you to care for them.
Note that giant onion leaves tend to turn yellow before or after the blooming of the large umbels, and so it helps to plant ground-covering perennials around the giant onion plants, to cover the wilted leaves and only let the flower stem stick out.
As for pot-growing giant onion, remember to water regularly because water needs are higher due to the fact that potted plants tend to dry off faster.
All giant onions carry their florets bunched into balls, but the size, the colour and the staying power of that ball depend on the variety. Here is how the named forms in this article differ.
| Variety | Flower colour | Height | What sets it apart |
|---|---|---|---|
| ‘Ambassador’ | Deep purple | Over 3 feet (1 m) flower stalk | Bloom as wide as your hand |
| ‘Mount Everest’ | White | Equally tall | The white-flowered alternative to ‘Ambassador’ |
| ‘Gladiator’ | Pinkish-violet | Tall giant allium | Softer hue than the deep purples |
| ‘Globemaster’ | Huge purple head | Tall giant allium | Sterile hybrid, holds its head for weeks and sows no seedlings |
Whichever you pick, tall stems line the back of a flower bed beautifully and cut well for bouquets.
These are stupendous plants. A few varieties will illustrate how amazing these flowers are:
‘Globemaster’ is a sterile hybrid, so it holds its huge head for weeks and will not scatter seedlings through the bed.
For drying allium stems, timing depends on the look you want: cut at peak bloom to keep more colour, or wait until the florets fade and seedheads firm for sculptural heads.
Giant onion is a perennial that grows quite easily and which will produce very beautiful purple blue flowers that can be up to 8 to 12 inches (20 to 30 cm) across.
Native to Europe and Asia, this ornamental onion belongs to the same genus as the following species: edible garlic, onion, shallot, chives and is in the same family as leek.
Giant onion varieties all boast superb flowers bunched up in balls and the size and color of this ball depends on the variety.
In flower beds or along edges, and also along a wall or simply plunked in the middle of the yard, the ornamental impact of this plant is guaranteed!
It is also used in flower bouquets, because the foliage and the flowers both can be used to make appealing bouquets.
For the taller species you can stake the stem to keep it from folding under the wind. Nice for this is to use bamboo, it is perfectly suited and actually enhances the visual impact of the plant.
