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All About Allium

Every year around this time our Horticulturists encounter one question above all others: “What is THAT?” Of our most perennially popular plants, the genus Allium stands out as a public favorite in the Fort Point Channel Parks. We currently have nine unique varieties of these marvelous bulbs, all varying in size, shape, or color. After a hugely successful bulb planting last fall, we have been quite pleased to see some of these varieties in the parks for the first time, along with a number of other new bulb additions. You may notice a familiar savory smell if you happen past one of the broken stalks of these plants, commonly known as ‘Ornamental Onions’.

Within the genus Allium are not only the globe-shaped flowers that we have come to adore, but also many staples of our culinary tastes: onions, garlic, chives, leeks, scallions, and shallots. Most of our Allium bulbs have an inflorescence (or cluster of flowers) called an ‘umbel’, which is defined by a number of flower stalks of equal length emerging from a fixed point, which in this case is at the top of the stem or ‘scape’. This form gives these bulbs a dramatic architecture that is extremely unique in the landscape. Not only have we observed the value of our Allium varieties in terms of aesthetics, but they also have proved to be excellent attractors of pollinators! Here is a guide to our many Allium, see how many you can spot in the parks!

The Star of Persia (Allium christophii) has an open umbel, with many flower stalks comprising a very large and loosely-formed globe. These flowers are muted purple with a silvery sheen.

The Star of Persia (Allium christophii)

Allium ‘Firmament’ produces a dark silvery-purple flower with an almost flat bottom. This half-globe is about the size of a baseball atop a two foot tall scape.

Allium ‘Firmament’

Allium giganteum is one of the tallest ornamental onions, and has a similarly dense purple umbel as ‘Globemaster’ but is only half as large.

Allium giganteum

Allium ‘Globemaster’ is one of the most popular hybrids in cultivation. These don’t grow as tall as other Allium, but produce large dense lilac-purple flowers up to 10 inches in diameter.

Allium ‘Globemaster’

Black Garlic (Allium nigrum) produces a somewhat flat umbel of dense white flowers, and grows up to two and a half feet tall. This unique species not only attracts plant enthusiasts, but it also seems to be popular with Eastern Tiger Swallowtail butterflies!

Black Garlic (Allium nigrum)

Allium schubertii is one of the most unique ornamental onions, with huge fireworks of flowers sitting on very short scapes. This bulb’s rosy star-shaped flowers are attached to stalks of unequal length, giving it a loose form with a very large diameter.

Allium schubertii

The Three-cornered Leek (Allium triquetrum) is our earliest blooming Allium, and a bit different from the rest of its showy globe-flowered relatives. This understated bulb has drooping white flowers that sit atop a single scape.

The Three-cornered Leek (Allium triquetrum)

Allium ‘White Giant’ grows up to five feet tall and has white flowers in a globe approximately 6 inches in diameter. This stunning variety blooms in late spring and is unfortunately finished this season, so if you didn’t get a chance to catch it this year make sure to mark your calendars for next year.

Allium ‘White Giant’

The last ornamental onion of the bunch is the Drumstick Allium (Allium sphaerocephalon), which won’t bloom for another couple of weeks. This Allium has a small egg-shaped flower head that starts off green and changes to wine-red over time. We just observed its first bud break today!

Drumstick Allium (Allium sphaerocephalon)