Wisteria macrostachya 'Blue Moon' (Kentucky Wisteria)

'Blue Moon' is the most cold-hardy wisteria in cultivation, and it adds something the Asian species cannot: reliable reblooming. Established plants typically produce two to three flushes of fragrant, lavender-blue flower clusters per growing season, with the main show in late spring followed by additional waves through summer. The racemes are shorter than Japanese wisteria but the repeat bloom more than compensates, and the plant behaves more politely in the garden, with a less aggressive spread.

Give 'Blue Moon' a strong structure to climb. It will eventually cover an arbor, pergola, or sturdy fence with vigor, and the weight of a mature plant is substantial. Full sun is essential for maximum flowering. Plants may take two to three years after planting to settle in and begin blooming well, so patience in the early years pays off in abundance later.

Prune twice a year for best results: once after the main bloom in early summer and again in late winter, cutting sideshoots back to two or three buds. Unlike its Asian relatives, 'Blue Moon' is far less likely to become invasive, which makes it a more responsible choice for Pacific Northwest gardens. The fragrance on a warm summer day is one of the finer garden experiences.