How to Grow and Care for Ambassador Allium

Big, Showy Flower for Your Spring Bulb Garden

Ambassador allium plants with light purple globe-shaped flower heads on tall stems

Th Spruce / Adrienne Legault

There are many types of alliums (also known as flowering onions), which grow to varying heights and flower head sizes. The 'Ambassador' allium is valued for being tall and for bearing large, six-inch globe-shaped flower heads, and its leaves are strap-like.

While they are related to such better-known plants as 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.

Botanical Name Allium 'Ambassador'
Common Name Ambassador allium, Ambassador flowering onion
Plant Type Bulb plant
Mature Size 46 inches tall
Sun Exposure Full sun
Soil Type Friable, evenly moist, and well-drained
Soil pH Slightly acidic to neutral
Bloom Time May to June
Flower Color Light purple
USDA Hardiness Zones 5 to 8
Native Area Northern Hemisphere
Toxicity Toxic to dogs and cats

Ambassador Allium Care

Plant spring-flowering alliums in the fall. The colder your climate, the earlier in autumn you should plant them. Thus gardeners living in USDA hardiness zone 5 should plant in October, while, at the opposite end of the spectrum, you should wait until December to plant the bulbs if you live in zone 8.

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.

Ambassador allium plant on tall stem with globe-shaped flowering heads with light purple petals closeup

Th Spruce / Adrienne Legault

Ambassador allium flowering head with light purple petals closeup

Th Spruce / Adrienne Legault

Ambassador allium flowering head with light purple star-shaped petals closeup

Th Spruce / Adrienne Legault

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.