A giant awakens

You may not know it, but there’s an astonishing plant in the San Gabriel Valley -- a Chinese wisteria of grand proportions and virtually unflagging fortitude.

The Sierra Madre Wistaria Vine (we’ll get to the name spelling later), widely acknowledged as the largest flowering plant on the planet, was planted in 1894 from a one-gallon can, purchased for three bits at a Monrovia nursery. The little whip grew to gargantuan size, devouring one house in the process and outliving many admirers. Today, its gnarled branches wander and weave across two private properties. Each year, more than a million lavender blossoms open in concert along the stems and proclaim the arrival of spring.

This legendary wisteria is certainly the largest, but it’s not the oldest of its kind. That honor may belong to a 1,300-year-old Japanese wisteria at a shrine in Murata, Japan.

Wisteria is a familiar and much beloved plant, revered for longevity and as an object of great beauty in and out of flower. Its popularity in the West burgeoned during the late 19th and early 20th centuries, when Art Nouveau and all things Asian were the rage. Claude Monet draped wisteria across his Japanese footbridge and immortalized its snowy cascades on canvas. Louis Comfort Tiffany and, some years later, Frank Lloyd Wright fused images of purple wisteria into elegant panels of leaded glass.

Wisteria blossoms are winged and pea-like, bunched in long pendulous clusters. Their evocative fragrance, strongest in Japanese wisteria, is sweet but never cloying -- alluring and fresh, like the sweet pea, its legume-family cousin. The color range is similar, too, in subdued shades of blue, purple, pink and white.

The individual flowers of Chinese wisteria (Wisteria sinensis), like the one in Sierra Madre, open all at once on still-leafless vines for a heart-stopping show. Foliage and flowers of Japanese wisteria (Wisteria floribunda) emerge together, with buds breaking gradually over a longer period.

In autumn, the long graceful leaflets turn golden, then drop to unveil the vine’s rough and burly structure. Wisteria is a liana, or woody climber, whose grip grows tighter with increasing bulk.

Those lovely pointed leaflets, numbering 13 to 19 on Japanese wisteria and usually 11 on Chinese, have another neat trick. Triggered by circadian rhythms, they fold in the evening, bending as if to sleep, and open again in the morning.

It’s hard to identify a leafless wisteria, but this fun fact may help: Japanese wisterias twine in a clockwise direction and Chinese grow counterclockwise. Though true, there are other kinds of wisteria, so it’s not a foolproof test. .

Speaking of biological clocks, wisterias bloom on their own schedules, varying slightly from year to year. When the time is right, fat velvety buds expand and elongate. And on the perfect day, when the plant thinks it’s “spring enough,” the rounded blossoms burst into the light.

Our warm spell should coax the Sierra Madre Wistaria Vine into bloom, and just in time. For one day a year, the homeowners open their gates to the public during the community’s annual Wistaria Festival and Village Celebration, which takes place Sunday.

If, after visiting the Sierra Madre giant, you want to re-create the vision at home, consider yourself forewarned: You need only one. Build a strong support system. And don’t baby it.

Though tough as can be, wisterias are high-maintenance. How does this beanstalk grow? “Rampant” and “enthusiastic” come to mind. “Indeterminate” too. So far-reaching is its grasp, Sunset’s “Western Garden Book” makes no commitment as to ultimate size. In short, pruning is mandatory.

Genetically programmed to head for other ZIP codes, wisterias need little encouragement. Soil with decent drainage is their sole requirement. They flourish in light shade but flower more generously in spots with full sun. Regular irrigation helps young plants expand, but mature vines are quite drought-tolerant.

Like other legumes, wisterias pull nitrogen from the environment and store it in little root nodules for easy access when needed. So, there’s no feeding required. Excess nitrogen makes them grow even faster, often at the expense of flowering.

Some wisterias are reluctant bloomers. Seedlings may wait 10 to 20 years before their first show. To avoid this problem, limit your selection to named cultivars that are propagated from cuttings.

Improper pruning can also prevent flowering. Winter pruning is tricky but recommended. Just watch where you cut, making sure to retain the large furry flower buds that promise spring color. The second and easiest time to prune is immediately after flowering.

Large flat seedpods follow the flowers. Left on the vine, dried pods cause an audible ruckus as they crack and expel their beans. It’s best to remove the pods early, to avoid the buckshot and to keep the poisonous seeds away from pets and children. (All parts of wisteria are toxic.)

Do you lust for wisteria but lack space for a climber? If so, purchase or train your own tree-form wisteria, a small weeping “standard.” Meticulous pruning is needed to maintain a compact umbrella, but the resulting effect is dramatic. Standards perform well in the ground and in large pots.

Even shorter on space? Wisteria is a popular subject for bonsai culture. As manipulated miniatures in shallow containers, they are styled to display their elegant flower clusters.

Wondering which wisteria to plant? The ultimate reference, “Wisterias,” by Peter Valder ($32.95, Timber Press), tempts us with many species and 60 cultivars. If fragrance is important, choose a Japanese wisteria. W. floribunda ‘Macrobotrys’ is coveted for it 3-foot-long pale purple flower clusters, but it’s hard to find. Easier quests include W. f. ‘Texas Purple,’ which blooms at an early age, and W. f. ‘Rosea,’ a strongly perfumed pink.

Chinese wisteria, with stouter clusters of lightly scented flowers, is most common here, and much too common in the southeastern U.S., where it’s a noxious weed (another good reason to remove those seed pods). Popular garden varieties include: W. sinensis ‘Texas White,’ and W. s. ‘Amethyst,’ a fairly fragrant purple.

Now, if all of those fancy words haven’t worn you out, consider the name Wisteria. Or was that “wistaria,” as the folks in Sierra Madre choose to call it? Here’s the scoop: The plant was named by Harvard’s British-born botanist Thomas Nuttall, to honor Philadelphia anatomy professor and Jefferson crony Dr. Casper Wistar. But when the official moniker was recorded, Wisteria was spelled with an E instead of an A. In scientific nomenclature, to avoid confusion, the first given name sticks. So everybody’s right: The correct botanical name is Wisteria, and wistaria is sometimes used as a common name.

And there’s one more word for this well-known climber: extraordinary.