Opening from rich violet buds, they bloom early in the season in late spring. Wisteria 'Okayama', Silky Wisteria 'Okayama', Wisteria venusta 'Okayama' Previous Next. long (10-15 cm), of fragrant, pea-like, pale lilac flowers with a large and conspicuous white spot. Strongly scented, award-winning Wisteria brachybotrys 'Okayama' produces masses of hanging sprays, up to 4-6 in.