The present invention is directed to a seed metering assembly comprised of a set of stand-alone modular seed metering units. Each seed metering unit is selectively driven by a common drive member, such as a drive shaft. When a seed metering unit is engaged with the drive member, the unit will meter granular material. On the other hand, when the seed metering unit is not engaged with the drive member, the metering unit will not meter granular material. Hence, the present invention provides a seed metering apparatus in which the number of seed metering units can be scaled to match the number of distribution headers of a seeding implement.