The present subject matter provides a vertical axis washing machine appliance with features for applying steam to articles disposed therein. The washing machine appliance can be configured for filling a sump of the appliance with fluid and activating a pump in order to drain the sump of fluid. After the pump is activated, the washing machine appliance can be configured for submerging a heater in the appliance's sump with fluid and also starting the heater in order to heat the fluid in the sump and generate steam. Related methods are also provided.