The ‘Blue Moon’ wisteria, a North American native (Wisteria macrostachya), is valued for its beautiful lavender-blue blooms and cold hardiness. While many wisteria species are known for aggressive growth, ‘Blue Moon’ differs significantly from its Asian counterparts, offering a less ecologically damaging alternative.
Understanding Wisteria Invasiveness
The general concern about wisteria stems primarily from non-native species, specifically Wisteria sinensis (Chinese Wisteria) and Wisteria floribunda (Japanese Wisteria), which are widely considered invasive in many regions of the United States. These Asian species exhibit aggressive growth habits, readily outcompeting native plants and forming dense thickets. Their woody vines twine tightly around host tree trunks and branches, frequently causing damage or death by girdling them. Furthermore, these invasive wisterias spread prolifically through viable seeds, which can be dispersed by water, and by rooting wherever their stems touch the ground.
In contrast, Wisteria frutescens ‘Blue Moon’, a cultivar of an American native, is not considered invasive in North America. It evolved within the continent’s ecosystem, producing fewer viable seeds and having a less aggressive root spread than its Asian relatives. While vigorous, ‘Blue Moon’ is less likely to outcompete native flora, integrating more harmoniously into the landscape.
Blue Moon Wisteria Growth Patterns
‘Blue Moon’ wisteria is a vigorous, deciduous climbing vine known for rapid growth and considerable size. It can reach a height of 15 to 25 feet, with a spread of 4 to 8 feet. Its stems twine around support structures. The plant features dense, deep green leaves, providing a lush backdrop for its striking flowers.
‘Blue Moon’ is exceptionally cold hardy, thriving in USDA Zones 3 to 9. It produces fragrant, lavender-blue, pea-like flowers in pendulous racemes, typically 6 to 12 inches long, appearing in late spring or early summer. Unlike many other wisteria varieties, ‘Blue Moon’ can rebloom multiple times in a single growing season, potentially flowering up to three times until the first frost. This repeat blooming extends its ornamental value.
Managing Blue Moon Wisteria
Despite its non-invasive nature, ‘Blue Moon’ wisteria is a robust grower benefiting from consistent management to maintain its form and encourage abundant blooms. Due to its size and weight, select a secure planting site with a sturdy support structure, such as an arbor, pergola, or strong trellis. Place it away from building foundations. The plant requires full sun exposure, at least six hours daily, for optimal flowering, though it can tolerate some afternoon shade in warmer climates.
Pruning controls the plant’s size, shapes it, and promotes prolific flowering. A two-stage approach is recommended: a dormant season prune in late winter or early spring, removing about half of the prior year’s growth and any dead or tangled stems. A summer prune after the first flush of blooms involves cutting back current year’s green shoots to five or six leaves, encouraging subsequent flower buds. This regular maintenance ensures the vine remains manageable and provides its striking floral display.