While they are related to such better-known plants as shallots, onions and garlic, flowering onions serve ornamental purposes. ‘Ambassador’ is one of the showiest; it adds great purple color and height to the late-spring bulb garden. It is one of the last of the large alliums to flower. How deep to plant allium bulbs is information that is usually provided on the packaging. But if it is not, the general rule of thumb is to plant bulbs two to three times the height of the bulb. For example, if a bulb measures two inches from nose to base, it needs to be planted four to six inches deep. Allium bulbs are large, so they are planted more deeply than daffodils or tulips. Deeply water bulbs at planting time, and thereafter let nature take care of the moisture.
Light
For optimal flowering, grow ‘Ambassador’ allium in full sun.
Soil
Grow ‘Ambassador’ allium in well-drained, sandy soil. Bulb rot can occur in overly moist soil. In terms of soil pH, alliums prefer a somewhat acidic soil but tolerates a neutral pH.
Water
Alliums prefer dry to medium moisture; it is a relatively drought-tolerant perennial.
Fertilizer
Fertilize allium bulbs in fall and spring with any well-balanced fertilizer.
Pruning
When alliums have finished flowering, you can remove the spent flower heads or leave them in place as an ornamental feature. As is the best practice for all spring bulbs, leave the foliage alone after blooming is finished. No matter how bad the foliage looks, resist the temptation to remove it until it has completely died down naturally. Alliums bulbs need their foliage to produce energy for next year’s flowers. Once the foliage has turned brown and has died down completely, use a gentle tug to remove it.
Propagating Ambassador Allium
To propagate overcrowded alliums, dig and divide the bulbs after the foliage has died back in late summer Separate the bulbs and replant them at the proper depth (two to three times the height of the bulb).
Bloom
When grown in USDA hardiness zone 5, the ‘Ambassador’ allium will begin blooming the third week in May and continue blooming until the second week in June. The plant becomes dormant in summer. Even after flowering has ended, an attractive dried seed head remains behind to offer visual interest in early summer.
Landscape Uses for Ambassador Allium
Juxtapose ‘Ambassador’ allium with a yellow, late-blooming tulip to create a sharp color contrast. It is also a good companion plant for rose bushes. Its tall stature makes it a logical choice for the back of a flower border. Such placement offers a bonus: the unsightly leaves of early summer will be hidden, as will the gap left behind when the plant goes dormant and disappears in mid-summer.
Common Pests
You might have to kill off slugs and snails to be able to successfully grow ‘Ambassador’ allium. Leaf miners can also be a problem. But unlike with crocus bulbs, for example, you will not have to worry about rodents digging up and eating the bulbs. Alliums are deer-resistant.
What Makes Ambassador Allium Special
You will hear some specialized terms when reading about flowering onions (although they are not unique to the Allium genus). Two of the terms are umbel and scape. “Umbel” and “umbrella” ultimately derive from the same Latin word. This fact makes it easier for beginners to remember that an umbel is a flower head composed of numerous short flower stalks fanning out from a central point (rather like the ribs of an umbrella). Meanwhile, a scape is a long, bare stalk that supports a flower (as opposed to a flower stalk that bears leaves somewhere between the ground and the flower). The ‘Ambassador’ cultivar stands out in two ways:
It bears a big umbel (often seven inches across) that is perfectly round and densely packed with tiny, star-shaped, light-purple flowers. While not the biggest of allium flower heads among the flowering onions (that of Allium schubertii, for example, is bigger), its size combined with its density makes it an impressive sight. It is one of the tallest flowering onions (the tallest examples may stand 46 inches tall). In fact, due to the height of its scape, some refer to it as a giant allium. This scape is very sturdy, making it good for floral arrangements.
