Allium is a genus from the amaryllis family (Amaryllidaceae) and is commonly named ornamental onion. Initially, Allium was classified within the lily family (Liliaceae), and later inthe onion family (Alliaceae). Currently Allium is placed in the subfamily Allioideae within the amaryllis family. Alliums are mostly found in temperate regions of the Northern Hemisphere. Onion (Allium cepa), garlic (Allium sativum), leek (Allium porrum) and chives (Allium schoenoprasum), amongst others, are well known culinary members of this genus.
The word “allium” is Latin for “garlic”.
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, lilac, purple, yellow, violet and pink flowers, many attract bees and some are fragrant. Alliums are widely used in both fresh and dried bouquets.
The nice thing about ornamental onions is that their flower stems rise well above the leaves, allowing you to fully enjoy the beautiful 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, as long as it is not freezing, 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) high, 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 that once the leaves have died. You can store the bulbs in a dry, dark place at room temperature, and replant them 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 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 plant needs the leaves to collect enough energy into the bulb 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: yes
Hardiness: -13 ºF/-25 ºC
Height: 4-60 inches/10-150 cm
Soil: normal/dry