Amethyst Falls American Wisteria

Wisteria frutescens ‘Amethyst Falls’

 The flower buds on Wisteria frutescens ‘Amethyst Falls’ start at the base of the raceme, and individual florets open to reveal their unique papilionaceous flowers. June 2025, UC Davis. Photo: JA Sisneroz

Summary

Wisteria frutescens is native to the American South, growing moist riverine habitats with a native range bounded by Virginia and Florida in the east, and Texas in the West. (Dirr, 1998) This is a relatively uncommon species compared to other Wisteria spp. While this species possesses the same racemes of purple, fragrant flowers associated with Wisteria sp., flowering occurs in late spring rather than early spring. The cultivar ‘Amethyst Falls’ grows in USDA Zones 5-9, with plants reputedly reaching up to 30’ in length. (Missouri BG)

As a genus, Wisteria spp. are classic climbing plants and there was an impetus to include one at the UC Davis trial due to its popularity. However, both of the Asian species commonly found in the trade W. floribunda and W. sinensis are considered invasive in certain parts of the US. Hence the selection of ‘Amethyst Falls’. Plants were obtained as 4” sized material in Spring 2023 and grown in #1 sized containers for several months before being planted in the field. While trials staff did weave stems throughout the trellises, no individual plant managed to cover a trellis by the end of the trial in 2025.

University of California Davis Results & Discussion

Plants pushed out new growth in the spring, with the bright green foliage covered in shiny silver hairs. Flowers began opening in May 2026, with periodic light re-bloom throughout the remainder of the season. In August and September some of the older foliage began to yellow and drop. While the foliage was typically acceptable, and the flowers were attractive, the lack of coverage weighed down overall appearance scores. While a few flowering plants scored overall appearance ratings of 4, most of the plants hovered around the threshold of acceptability scoring 2 or 3.

This was the least favorite plant of participants at the open house, regularly scoring amongst the lowest plants. At both events the mean overall appearance values for all contestants were lower than 3 for two of the three plants rated. Considering that 3 is the minimum level for aesthetic acceptability, this suggests that participants found this plant unappealing. Much like trials staff, participants seemed underwhelmed at the level of growth writing “with time I suspect this will be a great vine, but coverage was poor now” and “maybe they need more time”.  One optimistic participant noted “lacking vigor but that might be a plus” considering the aggressive reputation of other Wisteria sp. (Even Dirr calls the others “bullies”) (p. 1100, 1998). By September a number of participants suggested the plants were struggling and noted they might need water. Comments from two participants really sum up the performance of ‘Amethyst Falls’ - “pretty but a little too timid” and “the wisteria were my least favorite, they don’t look as good as the others.”