Here are three White cultivars that had
10 to 19 days of flowers (as of 06-28-25).

Exotic Perfume - 17 days
Spacecoast White Out - 10 days
Tuscawilla Snowdrift - 16 days

Exotic Perfume - 2 plants (8 fans), 6 inch flowers, 23 inches tall, pretty large flowers, midseason, semi-evergreen, bloomed May 4 to May 24, 17 days with flowers in 2025, 30 days with flowers in 2024 with a rebloom, 19 days with flowers in 2023, planted 07-04-22, Schreiner's

Spacecoast White Out - 1 plant (4 fans), 6.5 inch flowers, 24 inches tall, early, semi-evergreen, bloomed May 20 to Jun 3, 10 days with flowers in 2025, 8 days with flowers in 2024, 11 days with flowers in 2023, 15 days with flowers in 2022, planted 10-22-19, Breck's

Tuscawilla Snowdrift - 4 plants (14 fans), 6.75 inch flowers, 24 inches tall, flowers are huge and ruffled, the largest non-spider flowers I have, midseason late, evergreen, bloomed May 14 to Jun 26, 16 days with flowers in 2025, 5 days with flowers in 2024, gave away lots of fans in 2024, 43 days with flowers in 2023, 4 days with flowers in 2022, planted 03-05-22, Amador Flower Farm