Allocation models for annual plants predict that reproductive yield is maximized by an instantaneous switch from vegetative to reproductive growth. The switch is timed so that final reproductive yield is equal to the vegetative mass at the time of the switch, provided vegetative and reproductive growth efficiencies are equal. Measured allocation patterns for Plantago erecta and Clarkia rubicunda show a gradual shift from vegetative to reproductive growth in both species. This graded pattern results in a 5.5% decrease in reproductive yield for Plantago relative to the theoretical maximum. The timing of that graded pattern appears optimal.