Alliums burst into glorious spheres of bloom in late spring, as jaunty and debonair as the season. Fall is the time to plant them by the dozens.

Alliums are flashy blooms by any measure. Their globe-shaped flower heads, covered with an uncountable number of tiny star-shaped blossoms, have tremendous impact in a garden.

"They really add an exclamation point," says Christian Harper, a horticulturist at Olbrich Botanical Gardens in Madison, Wisconsin, who has been planting alliums in Olbrich's flowerbeds for more than 20 years. "There is just something about those globes from a distance," he says, "they appear to be floating, and they really pop."

The allium family of ornamental onions is dominated by great big blooms. Mail-order specialists offer the widest variety, with a dozen or more different types in some catalogs. Garden shops often have a good selection of several different alliums, usually including Globemaster, the biggest of them all, which has 10-inch purple globes of sparkling flowers on stems up to three feet tall. Globemaster's flowers last for a couple of glorious weeks in the garden. After they bloom, the sturdy flower heads remain decorative for months -- at this point, they're tawny, not purple, but there's simply nothing else in the garden world quite like these big round balls, and they hold their own while the roses and daylilies come along.

Besides Globemaster, there are purple alliums with somewhat smaller orbs of blooms, white-flowering alliums, alliums with looser heads of pink flowers, and sunny yellow alliums only about 10 inches tall. Garden designers prize them all for their great beauty and for their ability to bridge the season. Like a burst of fireworks at the end of spring, alliums lead the parade of summer flowers like a tall drum major at the head of a marching band. The earliest-blooming types loom above spring's last tulips, and the latest to bloom open with the roses.

Have fun with them. "I have a favorite, and it is Allium schubertii," says Barbara Katz, a garden designer in Washington, D.C. "It's like a constellation." Allium schubertii is an atypical allium, growing on stems only about 18 inches tall. The globe of blooms, on the other hand, is about 12 inches in diameter. Individual flower stems are of several different lengths: The effect is distinctly starlike, twinkling madly.

Katz also plants "a ton of Purple Sensation" alliums in her own and clients' gardens. The dark purple blooms stand about 30 inches tall. "I mix it with hostas, and it looks like the hostas are flowering," Katz says. "I plant it around hydrangeas. It's fun."

Katz and other designers purposely plant alliums among perennial flowers and shrubs because the strappy allium foliage is usually fading when its flowers come into bloom. A lively garden covers up the tired leaves, so you can admire the spectacular flowers all the better.

Purple Sensation allium is well-known for more than its great flowers: Among tall purple alliums, it is the greatest bargain. You can buy 25 bulbs for less than $20. Globemaster bulbs often cost $5 or more apiece. Ambassador, a tall purple allium with flower heads about six inches in diameter, is another expensive one, with bulbs at about $6 apiece.

They're all worth the investment. Alliums are known for their ability to persist in a garden for years. "They're easy and long-living, almost like perennial plants," says Jacqueline van der Kloet, a Dutch garden designer whose deft hand with flower bulbs and perennials has led to international garden projects, including some at Battery Park in New York City and Millennium Park in Chicago. (Both are collaborations with the naturalistic Dutch garden designer Piet Oudolf.)

Van der Kloet included Purple Sensation and the drumstick allium, A. sphaerocephalon in her bulb plantings at the Lurie garden in Chicago. She especially loves the smaller alliums, including the white-blooming bride's onion (A. neapolitanum), which is sometimes used in bridal bouquets. Good plants to include with all alliums are "plants that are rather modest," she says, "so the alliums will add just that touch of extra that makes the combination perfect." She suggests planting them with ornamental grasses, gaura, lavenders, catmint and cranesbill geraniums.

To take full advantage of the whole allium season, plant species and varieties that will bloom over a long time. Plant them in clusters of three or five bulbs, scattered here and there in flower beds. Planted this way, "it really looks like quite a lot is going on," says Christian Curless of Colorblends, a mail-order bulb specialty company that offers 11 different alliums in its catalog. Curless says that he, like many garden designers, "think of alliums as a little bit 'in-between season' plants," but it's time to change that. They create a season all their own, and share it graciously.

SIDEBAR

ALLIUMS IN ORDER

Fall is the time to plant alliums. If you plant both early- and late-blooming varieties, the season will last for weeks, from late spring through early summer. Some are so inexpensive that you can plant them by the dozen. More expensive alliums tend to be the largest-flowering types: Try three or five together, and prepare to stand back and watch the show when they bloom. Deer and rabbits do not like them. Here are some suggestions from bulb experts.

-- Christian Curless, of Colorblends, the mail-order bulb specialists, says the earliest allium in his catalog is Purple Sensation, which blooms "on the heels of tulips." Next up is Gladiator, which grows 40 inches tall, followed by the white-flowering Mount Everest, then Globemaster. "Nothing else in our catalog blooms as long as Globemaster," he says. The flowers are sterile, which may explain the long duration of bloom. Ambassador is one of the latest tall alliums to bloom. Its season overlaps with pink Knock Out roses.

-- Barbara Katz, a garden designer and owner of London Landscapes in the Washington, D.C., metro area, loves Allium schubertii, Purple Sensation and Gladiator. Globemaster, she says, "is almost over the top." She also recommends White Giant, with white globes of bloom, and drumstick allium, A. spaerocephalon, which blooms in early summer. Katz plants alliums in odd-numbered groups in a garden, buying a dozen or so bulbs. "With 25 alliums, you can make a very strong statement," she says.

-- Dutch designer Jacqueline van der Kloet, who has introduced fresh bulb combinations to the traditional world of Keukenhoff in Holland and to great public gardens around the world, likes Allium zebdanense, a tiny allium that blooms in very early spring, and the bridal onion, A. neapolitanum, which blooms in early May in her own garden. Her favorites to grow in mixed perennial gardens are Allium christophii, A. schubertii, A. atropurpureum and the drumstick allium. She also likes the new allium Summer Drummer, which grows up to seven feet tall and blooms in summer, with two-tone purple-and-white flowers on a round flower head the size of a big baseball.

SOURCES

-- Colorblends, www.colorblends.com

-- Brent and Becky's Bulbs, www.brentandbeckysbulbs.com

-- Van Engelen, www.vanengelen.com

(For editorial questions, please contact Clint Hooker at chooker@amuniversal.com.)

LATE BLOOMERS AND REBLOOMERS: THE GARDEN IN FALL

The changing season comes with a promise of splashy colors -- not just in the tree foliage, but in the garden, too. In a well-diversified garden, annuals, perennials and shrubs keep working long into fall and make this the garden's most refreshing season.

Garden shops traditionally stock up with chrysanthemums and pansies in the fall. They're typically in bloom or in bud when you buy them, and they keep right on blooming through cool autumn days. The selection is impressive, but these plants do not have exclusive rights to fall color: reblooming and late-blooming annuals, perennials and shrubs can be the backbone of a fall garden.

"Reblooming is more than a buzzword among breeders," says Natalia Hamill, a brand manager for Bailey's nursery, which developed the Endless Summer series of non-stop-blooming hydrangeas. "It's one of the first questions people ask," Hamill says. "The retail buyer wants to know: does it re-bloom? This is a goal for any spring or summer blooming plant."

Breeders have responded to the demand with plants that look great in summer's heat but really sparkle in the cooler, shorter days after Labor Day. It's a pleasure to be in the garden during this season -- summer's lushness lingers on, while the heat fades away.

Professionals actually use two terms to describe plants that keep blooming. Rebloomers are plants, such as many roses, that produce wave after wave of bloom from late spring through frost. Knock Out roses are the best-known reblooming shrub roses, but there are many other disease-resistant roses that look great all season long and keep blooming through the fall, including two dozen roses in Bailey's Easy Elegance series. Reblooming plants produce their flowers exclusively on each year's new growth.

Remontant plants are those that bloom both on the previous year's growth and on new growth, Hamill says. In the world of hydrangeas, remontant types are the hottest thing on the market. The buds that open early in the summer have wintered in the garden; in late summer and fall, more flowers are produced on new growth. For gardeners, the terminology is less important than the flowers themselves. Bloom Struck, the latest hydrangea in the Endless Summer series, is an especially prolific plant: It continues to produce flowers until the end of October, even in Minnesota.

Clipping off the spent blooms of annual flowers all summer long will encourage them to keep blooming through fall. Cosmos and zinnias come to mind, but marigolds are hearty rebloomers, whose cheerful yellow-and-orange palette suits the fall season perfectly. They're often available at garden shops in fall, alongside mums and pansies, in case you neglected to plant them in the spring.

Cutting spent blooms to encourage a new flush of flowers also works with some shrubs, such as crape myrtles, Hamill says. "Cut them back after they bloom in summer, and they will rebloom in September and October," she says. The new Bloomerang lilac will throw up flowers through the fall if you cut off old blooms, with either hedge shears or hand pruners, and they add a fine color to the fall palette. Butterfly bushes also continue to bloom if you keep them trimmed.

Hamill loves reblooming and remontant plants, but she doesn't rely on them alone. Ornamental grasses are at their exuberant best in fall. Asters and sedums come into bloom, attracting butterflies to the garden. Of course, there are the chrysanthemums and pansies. Trees and shrubs with red berries are bright spots in any garden, and they also attract migrating birds. "You really want layers of plants," Hamill says, "with foliage, flowers, seed heads, pretty textures."

Among foliage plants, the handsome leaves of ninebark Amber Jubilee or Coppertina will bring the fiery colors of the maples down to eye level; the large, quilted foliage of oak-leaf hydrangeas turns from green to a rich burgundy in fall. Tiger Eyes sumac, known for its attention-grabbing chartreuse foliage all summer long, turns an intense, dramatic orange in fall before the leaves drop, exposing striking straight stems that cast long shadows in the winter garden.

If summer flowerpots are getting tired, early fall is a great time to replant; garden shops are usually well-stocked right after Labor Day. "It's time to spruce up anything that looks bedraggled," says Chris Brown, greenhouse manager at White Oak Gardens in Cincinnati. The garden shop sells ornamental grasses, anemones and asters for flower beds or for fall pots. Like many gardens shops, White Oak Gardens also stocks a good supply of trees and shrubs, and fall is the ideal time to plant them. For serious gardeners, "it's a shot in the arm," Brown says.

There's no reason to slow down: Fall is a great time to plant, and a beautiful time of year to be in the garden, says Tom Hilgeman, the shop's general manager. Hydrangea paniculata, whose creamy panicles of blooms fade to a rich, deep blush, is one of his favorite fall plants. He also recommends shrub roses and spireas for fall gardens. Shrubs you plant in the fall will not grow much before winter sets in; but water them well, and they'll send roots down and settle in. Next spring, they'll be ready to grow -- and to keep on looking good all the way through to the end of fall.

(For editorial questions, please contact Clint Hooker at chooker@amuniversal.com.)

Butterflies are a wonderful part of a healthy garden. They -- and innumerable other insects that pollinate plants -- are also ecologically and economically vital, but they are on the decline.

Gardeners can help offset the loss by planting flowers that sustain butterflies and other pollinators. A garden designed with pollinators in mind is as beautiful as any other, and perhaps even more so.

Butterflies, moths, bees, beetles, hummingbirds and even bats all are pollinators. Their health and welfare are critical to a healthy and diverse ecosystem, and to the production of one in every three bites of food we take, according to the National Pollinator Garden Network. The organization has just launched an ambitious campaign, the Million Pollinator Garden Challenge, to encourage the planting of pollinator-friendly landscapes to invigorate pollinator populations. The goal is to register one million pollinator gardens, large and small, old and new, across the country.

"If you have four acres, that would be wonderful," says Matthew Shepherd, communications director for the Xerces Society, the wildlife conservation and protection organization. "But if you have an urban plot, a community garden, or a spot on the balcony of your 10th-floor condo, you can plant flowers," he says. "You can do that anywhere."

Monarch butterflies are perhaps all pollinators' most widely recognized ambassador, and they are among the most endangered. Millions of acres of the natural habitat of this flashy orange-and-black butterfly have been lost to development and to the use of agricultural herbicides. The Monarch Watch program, which encourages gardeners to plant milkweed (the leaves of these plants are the only food monarch caterpillars eat) has raised considerable public awareness; the program is among the 25 partners in the Million Pollinator Garden Challenge.

Perhaps the most prominent pollinator garden in the world is the Butterfly Habitat Garden at the Smithsonian's National Museum of Natural History on the Mall in Washington, D.C. The garden was established in 1995, and next year, it will have a new name: the Pollinator Garden. "It's time to tell the broader message," says James Gagliardi, lead horticulturist with Smithsonian Gardens at the Natural History Museum. "A lot of people are fearful or just don't like insect activity," he says. "But it's very positive. Flowers and fruits are not going to be around without these pollinators."

A gardener's role in all this is easy: Plant flowers. The blooms you already love are likely to be among those preferred by butterflies and other pollinators.

Native plants rub shoulders with non-natives in the Butterfly Habitat Garden. Gagliardi grows native perennials such as goldenrod, which blooms in the fall, and mountain mint, which has silvery leaves and tiny pink flowers, and attracts an abundance of pollinators. He also grows bright annuals, among them zinnias, which are a magnet for butterflies, and Mexican sunflower, a tall plant covered with bright orange flowers -- and pollinators -- in late summer and fall.

Big sweeps of colorful flowers blooming through the summer are important, but the most effective and successful pollinator gardens have blooms throughout the season, from earliest spring until a hard frost. Trees, shrubs and vines also fit into the picture.

"Just by planting one tree, you can really make a difference," says Peggy Anne Montgomery of American Beauties Native Plants, another partner in the Million Pollinator Garden Challenge. A mighty oak would be great, she says, but so are many small trees, such as serviceberry, "a lovely small tree that supplies nectar and berries, and has great fall color."

Montgomery relies as much as possible on native plants, with which North American pollinators are likely to have well-established ecological relationships. She recommends long-blooming native perennial coneflowers, phlox and ironweed. Include butterfly milkweed and ornamental grasses in your pollinator garden, too, she says, creating layered plantings that look rich and full, help hold each other up through summer wind and rain, and provide shelter for insects during the winter.

Renee Shepherd, owner of the seed company Renee's Garden, says that annual flowers grown from seed are every gardener's gateway plants to a colorful and easy pollinator-friendly garden. Annual sunflowers, cosmos, zinnias, cleome and alyssum all attract butterflies and other pollinators. Herbs should be part of the mix, she says: Plant plenty of them, let them bloom and see how many pollinators they attract. Shepherd likes cilantro, arugula, basil and chives both for their taste and because they attract so many pollinators. She practices succession planting, so she always has fresh herbs for the kitchen and blooming herbs outside for the pollinators.

Of course, pollinators find their way to vegetable gardens, too. Beans, squash, tomatoes and cucumbers all attract pollinators, but you'll have more pollinators -- and more impressive harvests -- in a vegetable garden that includes flowers. "The more diversity you have, the more pollinators," Shepherd says.

Above all, a pollinator garden is no place for pesticides. "We don't use them" in the Butterfly Habitat Garden, Gagliardi says. "Our garden is very healthy and very balanced, too." Visitors might notice holes in the leaves of a few plants, or they may discover curious striped caterpillars on the fennel or dill, "but if you want butterflies, you have to have food sources, and there are going to be holes in the leaves," Gagliardi says. Instead of fretting over insect damage, get to know the insects. In a pollinator garden, you'll have plenty to discover. Together with the flowers, these pretty pollinators put on quite a show.

SOURCES:

-- The Million Pollinator Garden Challenge, launched this summer by the National Pollinator Garden Network, is a campaign to register one million public and private gardens and landscapes that support pollinators. To get your garden on the map: millionpollinatorgardens.org.

-- The Butterfly Habitat Garden at the Smithsonian's National Museum of Natural History beautifully demonstrates the relationships between plants and butterflies and other pollinators. The garden is open every day, year round. Tours are available. For more information and a description of the garden's habitats, a butterfly list and tips on gardening for pollinators: gardens.si.edu.

-- The Xerces Society is a conservation organization dedicated to research, outreach and education. The society is a partner in the Million Pollinator Garden Challenge. Pollinator Conservation resources on the Xerces Society's website include excellent regional lists for pollinator plants. xerces.org

-- Renee's Garden sells heirloom and new varieties of vegetable and flower seeds, emphasizing easy-to-grow, delicious and beautiful crops and flowers. The company is committed to organic gardening and good gardening practices. reneesgarden.com

-- American Beauties Native Plants has introduced a wide variety of native plants at garden shops through a branded-plant program, making many previously hard-to-obtain natives accessible to gardeners. The company's website includes several easy plans and plant lists for pollinator-friendly gardens. abnativeplants.com

(For editorial questions, please contact Clint Hooker at chooker@amuniversal.com.)