(News article for March 16, 2024; edited)

You may have noticed wisteria blooming recently in yards and along roadsides. I find wisteria’s flowers lovely, but Chinese wisteria (Wisteria sinensis) and Japanese wisteria (W. floribunda) are quite aggressive and can overtake trees if not managed. They’re considered invasive by many.

If you choose to grow one of these, make sure you don’t let it spread into unmanaged areas. One option is to plant the vine by itself, in the middle of a mowed area. One can grow Chinese or Japanese wisteria on a trellis, but ensure that the trellis is very strong. Wooden structures may eventually collapse under wisteria’s weight.

It can be difficult to distinguish between Chinese and Japanese wisteria, though there are differences. Leaves of Japanese wisteria emerge earlier than those of Chinese wisteria. Chinese wisteria generally starts blooming before it leafs out. Flower clusters (racemes) of Japanese wisteria tend to be about 8 to 20 inches long, compared with 6 to 12 inches for Chinese wisteria. Japanese wisteria doesn’t generally have as many flowers at one time as Chinese wisteria does but flowers over a longer period. Chinese wisteria vines climb by twining counterclockwise, and Japanese wisteria twines in a clockwise direction.

While Chinese and Japanese wisterias are more common in landscapes, American wisteria (W. frutescens) is a non-invasive alternative that’s native to Louisiana and most of the eastern US. In the wild, it tends to grow on moist or wet sites such as streambanks. Flowering begins later in the spring than on Chinese and Japanese wisterias and continues during the summer. (Unlike the other two, American wisteria flowers primarily on new growth.) Flower clusters reach 4 to 6 inches long and support bees and butterflies. Adequate sun exposure is needed for good flower production. Cultivars include ‘Amethyst Falls’, which has lavender-purple flowers, and the white-flowered ‘Nivea’. American wisteria is considered hardy in USDA Hardiness Zones 5 through 9, so it’s suitable, temperature-wise, for most of Louisiana.

Another alternative to the more invasive wisterias is evergreen wisteria (Wisteriopsis reticulata; AKA Millettia reticulata or Callerya reticulata). This vine is native to Asia but isn’t as aggressive its Chinese and Japanese wisteria cousins. An additional feature is that it’s partially or fully evergreen in Zones 9 and 10. It’s cold hardy enough for Zone 8, too, but likely to lose its leaves in the winter there. Evergreen wisteria blooms in summer and fall, producing purple racemes that reach 6 to 10 inches long.

Evergreen wisteria isn’t considered a true wisteria but is a cousin within the bean or pea family (Fabaceae). Next week, I’ll discuss some other relatives, the indigos and wild or false indigos.

Let me know if you have questions.

Contact Mary Helen Ferguson, Ph.D.

Chinese wisteria (Photo: Larry Allain, U.S. Geological Survey)

American wisteria (Photo: Gena Todia, Wetland Resources Environmental Consulting, Bugwood.org)

Evergreen wisteria (Photo: Maryann Debski, JC Raulston Arboretum photograph collection)