Allium is a genus from the amaryllis family (Amaryllidaceae) and is commonly named ornamental onion. Formerly the Allium was classified as belonging to the Liliaceae family and later to the Alliaceae family. Currently the Allium is placed in the subfamily Allioideae within the amaryllis family. Alliums occur mostly in temperate regions of the Northern Hemisphere. Onion, garlic, leek and chives, amongst others, are well known culinary members of this genus.
There are many species, so you should be able to find one to your liking. There are early and late flowering species. They are available in different heights (4-60 inches (10 cm to 1.5 m)) and with a different need for sunlight. There are species with white, purple, yellow, violet and pink flowers, many attract bees and some are fragrant. Alliums make excellent cut flowers for fresh and dried bouquets.
The nice thing about ornamental onions is that their scapes rise far above the leaves so that you can fully enjoy the flowers. The flower stalks are sturdy and usually do not need support.
It is best the plant the bulbs late in the year, between October and December, if it does not freeze, in well-drained soil. Most Alliums prefer a sunny spot. Plant the bulbs with the pointy side up and two to three times as deep as the height of the bulb. So if the bulb is 2 inches (5 cm) heigh, you should plant it 4 to 6 inches (10 to 15 cm) deep. You can leave the bulbs in the ground. They will return the next year.
If you want to dig up the bulbs, you can do so if the leaves have withered and died. You can store the bulbs in a dry, dark place at room temperature and plant them in the ground again between October and December. It is best to plant them in a different location to prevent the possible transfer of diseases.
Something that is less attractive about the Allium is the foliage. The leaves start to wither even before the ornamental onion starts to bloom. It is best to leave the leaves on the plant until they have fully died. The Allium needs the leaves to collect enough energy to produce flowers the next year. You can plant other plants around the Allium to hide the ugly leaves.
Many ornamental onions spread through seed. If you do not want that, you should cut away the flowers stems before the seeds ripen.
Some Alliums may also spread through little new bulbs and rhizomes. The ornamental onion can produce small bulbs next to the old one in the ground, but they may also produce bulbils at the top of the flowering stem.
It may take a few years before seedlings and the new bulbs will bloom.
Attracts bees: yes
Characteristic: newly emerging every year
Deer resistant: yes
Exposure: sun/ part shade
Flower color: various
Flowering time: April – July
Foliage color: green
Fragrant flower: no
Hardiness: -13 ºF (-25 ºC)
Height: 4-60 inches (10-150 cm)