Alliums are often overlooked as one of the best bulbs for constant color throughout the seasons. Part of the problem is their common name: ornamental onion, which conjures up images of supermarket onions in shades of lime green or red. Alliums actually come in oval, spherical, or globular flower shapes, blooming in magnificent colors atop tall stems.
Because good perennial-garden designs are often made up of contrasting shapes, alliums’ rounded blooms make them great components for interesting garden combinations (not to mention that deer generally avoid them—to escape onion breath). Pair them with spikes or other large-leaved perennials to hide any decaying foliage.
It’s easy to think of alliums simply as colorful summer plants, but these easy-to-grow bulbs have options that will keep the blooms coming right up to the first frost. You’ll find outstanding choices here that will make you reconsider alliums as your new seasonal companions.
Hardiness: Alliums can be grown in Zones 3 to 9, depending upon the species and cultivar.
Alliums aren’t too picky: In most cases, alliums grow in average garden soil and need full sun and good drainage. The drainage is critical because so many of the bulbs are huge and will rot with too much moisture.
Aside from that, they are easy to grow and come back year after year with almost no maintenance. Occasionally, they need dividing after a few years, when you start to notice a decrease in flower production (usually this pertains to those with small bulbs). One of the best things about alliums is that most animals, especially deer, find the taste unappealing and won’t nibble on the leaves.
Plant them in fall: Alliums go in while leaves are falling. Average planting depth should be about three times the diameter of the bulb. I have planted alliums late in fall right up to Thanksgiving. Just be sure the ground hasn’t frozen yet so that the bulbs have time to take root.
Video: How to Plant Alliums
Spring is for more than just daffodils and tulips
In late spring, ‘Jeannine’ golden onion (USDA Hardiness Zones 3–9) emerges, growing a scant foot tall. It has two stems of individual, star-shaped, golden yellow flowers forming a circular floret. I love ‘Jeannine’ for the ease with which its soft, straplike, blue-green leaves tuck between the wonderful blue flowers of late spring to early summer. To get any kind of display, plant at least a dozen bulbs. ‘Jeannine’ multiplies continuously and, in a few years, will put on quite a show. If you love large drifts of golden daffodils, you will be equally impressed with this small golden treasure.
After viewing this average-size garden gem, moving on to something that looks like a giant lollipop on a stick is a shocker. Giant onion (Zones 5–9) is all that its name implies, peeking out in late spring and growing up tall and bold. The 4-inch-diameter flower is a pretty shade of lilac, but the large leaves are troublesome, turning yellow even before full flowering is complete. If this plant is not placed in the back of a border, it will need a hardy perennial to cover its dying foliage. Giant onion’s flowers are long blooming and are excellent to use as cut flowers. When planting, leave plenty of room for these large bulbs to grow.
In late spring, the short, squat Turkestan onion (Zones 5–9) flowers. This is my kind of plant, standing a mere 1 foot tall. The thick leaves on this onion are a showy gray-green mottled with shades of purple and a sort of reddish edge. The long-blooming flower is a pale silver-lavender. Even after flowering, do not remove the spent flower because it dries well. During a previous year, I spray-painted one to make a fairy wand for my daughter’s Halloween costume. For those who dare to be different, try spray painting them in your garden; it creates a funky effect. Plant Turkestan onion in groups of three or five for maximum impact. It looks great with ‘Caradonna’ blue sage (Salvia nemorosa ‘Caradonna’, Zones 5–9) in the background—a dramatic combo.
A handsome plant that has been grown since Victorian times is tumbleweed onion (Zones 4–9). The flowers are rose purple and begin to form on short stems. The infertile flowers shoot out, giving the effect of fireworks. Tumbleweed onion has an open, airy look rather than a compact head. The leaves go fast after flowering, but the seed head will look good for a while. It will eventually drop off and begin to roll around the garden, just like a tumbleweed in the Old West.
Waterwise bulbs keep summer rolling
Summer-flowering alliums display quite a bit of diversity. Nodding onion (Zones 4–8) is a northeastern native bulb. Light pink and dainty, it gets its common name because its flowers hang down. Nodding onion starts flowering in early summer and has a long bloom period. Because this allium stands only 18 inches tall, it easily tucks in between spring- and summer-flowering perennials. For those who have never grown this bulb, be aware that it always nods. This does not mean it needs water.
One of the colors that people love in perennial borders is blue. Blue globe onion (Zones 4–10) is an exceptional combination of dark and light blues melded together. The spherelike flowers reach 24 inches tall and work well for cut arrangements. Pair this variety with ‘Becky’ Shasta daisy (Leucanthemum × superbum ‘Becky’, Zones 5–8) or ‘Silver Moon’ Stokes’ aster (Stokesia laevis ‘Silver Moon’, Zones 5–9), both of which have daisylike white flowers that are a great color contrast. This bulb loves to grow hot and dry, so avoid sprinkler systems that keep the soil moist.
Another allium with the wow factor is stars of Persia (Zones 5–8). It has a 10-inch-diameter globe of striking light amethyst with silver shadings and green eyes. It is a large bulb, so leave space to optimize its full potential. The leaves are covered with white hairs—hence, it’s other common name: downy onion. It’s a great dried flower, but don’t plant it in the front of the border, unless deteriorating foliage turns you on. It’s tall and needs full sun, so place it behind any plant 10 inches or shorter.
Round out the growing season with these colorful oddballs
One of my favorite summer bulbs is black onion (Zones 5–8). The star-shaped flowers are white, but the centers are dark black to dark green, providing great contrast. Some designers don’t like the often-washed-out appearance of white flowers, but the black centers of this allium are strong enough that even picky gardeners will like it. Its striking 4- to 6-inch-diameter flowers bloom for several weeks, but even afterward, the seed heads look fine for a while (for those of you nondeadheading enthusiasts). Pair this with some of the chocolate-colored heucheras (Heuchera spp. and cvs., Zones 3–8) or any other dark-leaved plant for some subtle color echoing.
Drumstick allium (Zones 4–9)—I assume “drumstick” refers to a drumstick on a chicken rather than the kind used to play drums—is a great summer favorite of mine. I love this egg-shaped flower, which tends to naturalize in my garden. When other full-sun flowers fade, this beauty maintains its hot color. The crimson-purple flowers are very compact. Because they flower in midsummer, when golden daisies are rampant, you have an easy, no-fail combo. I like the extended bloom time of about three to four weeks, but once again, the foliage begins to turn yellow while the flowers still look great.
If you haven’t seen ‘Hair’ allium (Zones 4–8), it looks like it put its roots in an electric socket. Each stem produces several thin, tentacle-like green flowers from a purple base. Pair ‘Hair’ with anything that you think is rather boring because this bulb will catch your attention (even if you are not partial to such a weird plant).
Circle onion (Zones 4–9) is a very cool plant. The blue-green leaves give a corkscrew effect—hence, its nickname. Circle onion’s flower is a deeper pink than the species and, with its showier foliage, is more desirable. Try it in rock gardens or the front of the border; the curly onion looks most dramatic in Japanese-style gardens.
Fall is for flowers, and alliums are no exception. ‘Ozawa’ Japanese onion (Zones 4–9) starts to bloom in September, when most plants are winding down (but it sometimes goes to frost in my cold Zone 6). The good news is that, because it blooms so late, the shiny, narrow foliage never looks bad. The starlike purple flowers give the illusion of being large on such a small plant. Combine it with any of the white asters or mums available at this time of year.
If this article, with all of its offerings of colorful alliums from spring to fall, has not made you into an “alliophile,” then I just have to remind you: If you want to keep deer out, this is the bulb for you. Your garden will be beautiful and deer-free all season.
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