Wisteria a Fine Vine--and Pretty Good Shrub

Few plants add elegance and romance to the landscape like wisteria with its soft foliage and large, drooping clusters of perfumed flowers. Although wisteria is actually a vigorous deciduous vine, it can also be trained as a tree or shrub.

Now’s a good time to plant wisteria. Although most wisteria is currently dormant, plants should start budding in the next few weeks and will bloom in April or May. Some established vines even bloom into the summer months, says Jim Kitano, manager of Kitano Garden Center in La Palma.

There are about 10 species of wisteria, but the type most commonly found here is the Wisteria sinensis, which is native to China.

Varieties of the Chinese wisteria include ‘Alba,’ which has white flower clusters reaching 2 feet; ‘Caroline,’ with dark purple-blue flowers; and ‘Cooke’s Special,’ which has deep purple blooms. The latter variety is popular because it has a long blooming period that starts in spring and goes into summer.

To have luck growing this eye-catching vine, keep the following tips in mind:

* Plant in full sun in an area that gets a minimum of six hours of direct sunlight a day.

* When growing as a vine, choose an area where the plant will be able to spread, because wisteria vines can grow indefinitely, some reaching 120 feet. The vine will need a sturdy structure to grow on, such as an arbor, patio roof or fence.

* To grow as a tree or shrub, buy one that has been trained in this manner or prune and train it. To do so, remove all but one main stem and stake this securely with plastic horticultural tape.

When the plant has reached the height you wish the main branches to emerge from, pinch the plant at that level to force branching and rub off any buds that form below this point.

* Provide good drainage. Wisteria isn’t fussy about soil, but it can’t tolerate wet feet. Check drainage in an area by filling a 2-foot-deep hole with water until it will no longer drain. When you return 24 hours later, it should have completely drained. If there is standing water, choose a more well-draining site.

Before planting, break up hard clay by amending with one-third planter’s mix and digging down 2 1/2 feet.

* Plant wisteria with the graft union an inch or two above ground.

Once growth occurs, water wisteria a couple of times a week when there is no rain. Established plants 3 years or older need a good soaking once a week in warm weather.

* Fertilize three times a year. In spring and summer, use a fertilizer high in nitrogen, which will promote overall growth, such as a 16-16-16. In fall, use a fertilizer higher in phosphorus and potassium such as a 5-20-10. This will encourage strong roots and good flowering.

* To grow wisteria in a container, choose a pot that has at least 20-gallon capacity. Use a high-quality potting soil and water every three to five days, depending on the weather. Feed as you would in-ground plants.

* After a year of growth, prune wisteria when plant finishes blooming in late spring or early summer. Trim to control size and shape.

For more information, consult “Wisterias: A Comprehensive Guide,” which is available for $33 through Wayside Gardens, (800) 845-1124.