Double-edged sword of springtime vines

Wisteria: Gardeners love its graceful clusters of fragrant flowers, but lament its invasiveness.

March 25, 2001|By Ary Bruno | Ary Bruno,SPECIAL TO THE SUN

Certain plants inspire ambivalence in the horticultural heart. Like Jekyll and Hyde or the two-faced Roman god Janus, they exhibit a split personality that both endears them to and exasperates the gardener.

For example, I have Wisteria sinensis planted at the southwest corner of my front porch. It is 7 years old and has been blooming for three years.

On the plus side, this is a lovely, graceful, vining plant. It is awesome in springtime as it leafs out and flowers with large, fragrant racemes of purple-blue blossoms.

It provides nice shade in a hard-to-manage site at the edge of a driveway. Additionally it has withstood repeated droughts and Baltimore summer humidity well.

On the other hand, this is not a plant to underestimate: it will invade gutters and roof shingles with passionate abandon, snarl around telephone and electrical wires with glee, and send up deep-rooted suckers several feet away from the mother-plant. Peter Valder, author of Wisteria (Timberpress, 2000) and a retired botany professor from the University of Sydney, Australia, is quick with sympathy for my plight.

"Yes, wisteria is easy to grow, as you have discovered. With the Chinese and Japanese kinds it's largely a matter of being ready with the secateurs and fighting them back," he laughs.

"I became interested in wisterias because they didn't need any attention other than pruning and nothing ever seemed to go wrong with them. So I read up on them and began importing them from all over the world."

Best known and most available are W. sinensis originating in China, and W. floribunda from Japan. Both will climb merrily up to 40 feet, and are available with either purple or white flowers. W. floribunda also has a pink cultivar, "Plena.' Besides these, there are other species available which the gardener should consider.

One is our own native wisteria, W. frutescens. This is a less invasive plant (20 to 30 feet), highly adapted to our climate, which flowers later in the season on the ends of the current year's growth after the leaves have appeared.

While offered most often in white, a new cultivar `Amethyst Falls' has vivid, lavender-blue falls. It has the added attraction of flowering the first year.

W. macrostachya, or Kentucky wisteria, once considered a separate species, is now listed as a variety of W. frutescens. `Clara Mack' is a reblooming cultivar with showy white flowers.

For those who become seriously enamored, there are also more exotic species to seek out (though not necessarily more beautiful). W. brevidentata, W. praecox and W. villosa, from China; and W. brachybotrys and W. ventusa from Japan are some to try.

Valder says that when he first started he "read up and began importing them from all over the world.

"During this time I spent a fortune buying wisteria with different names only to find out when they eventually flowered that they were all (pretty much) the same."

All wisterias grow and flower best in full sun, and in a moist, well-drained soil. While wisterias will grow reluctantly in shady, dry ground, do not expect the grand floral show for which it is famous.

Valder recommends using the shorter racemed types against a wall, while the varieties with longer flower clusters do better where their flowers can hang free and be admired, such as on a pergola. In Japan it is considered especially desirable and artistic to grow the vines up a sturdy pine tree.

If space is a concern, or you don't enjoy the task of rooting out errant suckers, try growing wisteria in a container, or even as a bonsai. Plastic or concrete barriers like those used for running bamboo are also effective.

Wisteria is a fast grower, and will cover unsightly walls or views within a season or two. However, it does need very strong support.

When buying plants, Valder's advice is "to get plants on their own roots, even though they may take slightly longer to flower."

The reason for this, he says, is that "with grafted plants the scion can easily get swamped by suckers from the rootstock."

As for encouraging plants to bloom, the key lies in pruning and not giving too much fertilizer.

Nitrogen fertilizers tend to stimulate vegetative growth rather than flower buds. In fact, counsels Valder, it is better to avoid fertilizer at all "unless the plant looks starved."

He cautions, too, about pruning. "If you prune heavily in autumn or winter you'll cut off most of the branches that have set buds. However, I have found that keeping the plants carefully pruned in summer ensures a good (flower) bud set."

To do this he recommends shortening back the long growths that appear after flowering to two or three leaves, and then shortening back any long shoots which grow subsequently.

Of course, once you get the hang of them, you may not want to stop. Like Valder you may find yourself wondering where to put them. His solution?

"Eventually, as we had all given up tennis, we planted most of them on the fences of the tennis court and made it into a wisteria garden."

SOURCES

Wayside Gardens

1 Garden Lane

Hodges, SC 29695-0001

800-845-1124

www.waysidegardens.com

White Flower Farm

P.O. Box 50

Litchfield, CT 06759-0050

800-503-9624

www.whiteflowerfarm.com

Myseasons.com

800-806-1972

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