Here are some sources for pitahaya fruit and plants. White-fleshed varieties are usually called dragon fruit. At Vietnamese stores and nurseries, you might need to ask for thanh long.
* Bien Hoa Farm. Dragon fruit plants and fruits. Open weekends, 8 a.m. to 5 p.m. 275 Stewart Canyon Road, Fallbrook; (760) 728-8768.
* Dalat Farm. Dragon fruit plants and fruits, in limited supply. Open Monday through Friday, 8 a.m. to 6 p.m. 11130 E. Riverside Drive, Ontario (between Haven and Milliken avenues, under the power lines).
* Melissa's World Variety Produce. Dragon fruit by mail-order. (800) 588-0151.
* Mimosa Nursery (Anaheim). Dragon fruit plants in 7-gallon pots, $49. Open daily, 8 a.m. to 5 p.m. 2700 W. Crescent Ave, Anaheim. (714) 828-0780.