A couple months after the strike erupted, Chavez and Huerta, on a suggestion from attorney Stewart Weinberg, initiated a crucial tactic, one that the farmworkers used to remarkable effect: a consumer grape boycott. The union called upon the public to refrain from buying grapes without a union label. Union volunteers were sent out to big cities, where they established boycott centers that organized friendly groups—unions, churches, community organizations—to not buy grapes and to publicize the boycott and pressure stores to remove grapes from their shelves.

This was not a first. The National Farm Labor Union had used the tactic with some success during the DiGiorgio strike. But the grape strike took things to a new level. Combined with the union’s public disavowal of violence, this boycott was better funded, more extensive, more organized, and more effective. For one thing, it included a secondary boycott of stores selling grapes, not simply the primary boycott of the product itself. Although part of the difficulty farmworkers faced in organizing stemmed from their exclusion from the National Labor Relations Act, an advantage of being outside the law was their ability to use secondary boycotts, which had been removed from the NLRA by Taft-Hartley in 1947.