As the organic food sector has grownand changed to become more mainstream, large-scaleconventional growers have entered into organicproduction. While it is increasingly clear that notall organic farms are self-sufficient small scaleunits that practice poly-cultural agronomy and sell inlocal marketing venues, there still exists apresumption that there are clear lines between thesmall scale ``movement'' farmers who followagro-ecological agronomic ideals and the relativelylarger and partly conventional newcomers who do not.This paper addresses a specific empirical issue, whichis the extent to which California organic farmerspractice the techniques of ecological farming. Itillustrates that while there are some distinctdifferences in practices between larger and/orpart-conventional (i.e., mixed) growers and smallerand/or all-organic growers, it also shows that inalmost all cases, practices fall quite short ofagro-ecological ideals. By examining in more depth howgrowers follow particular agro-ecological principles,the paper also demonstrates that key variations arerelated to variables separate from scale. Some ofthese variables are geographic, ranging frombiophysical and climatic opportunities andconstraints, to regional norms and institutionalsupport. Mostly, however, variation is related to cropspecificities and the availability of efficacioustechnologies to deal with crop-specific problems. Thisso-called technology barrier crucially depends on howorganic is defined, and thus suggests the importanceof organic rules and regulations in shaping thepractices of organic production.