The Eschscholzia californica (California poppy) growing in the Ben Lomond sand hills of Santa Cruz county, California with its striking purple and white-colored leaves, may differ from other populations in the surrounding area. To quantify these differences, populations in coastal, sand hills, and serpentine soils were compared. Phenotypic data were collected from the field in 1998 and 1999. A common garden experiment was also performed. The sand hills population differs from both the coastal and the serpentine populations for the leaf characters examined. Population differentiation occurred among all three sites for at least some of the floral characters examined. The common garden experiment indicates that many of the difference among the populations are heritable, and are not a direct response to soil type.

Key words: Eschscholzia californica , ecotype, leaf color, population differentiation, sand, serpentine