Abstract: A seeder for depositing seeds in trays or substrate in a pattern of seed positions. The seeder includes a seed supply; and a conveyor configured to transfer seeds from the seed supply to the trays or substrate and release extracted seeds in the pattern of seed positions into the trays or substrate. A detector includes a light source and a sensor configured to detect seeds at seed holding positions of the conveyor in transfer from the seed supply to the trays or substrate and generate a signal. The light source is obliquely oriented to generate grazing light on or over the conveyor, for seeds to cast detectable shadows on the surface of the conveyor, and the sensor is oriented to detect shadows on the conveyor, cast by seeds at seed holding positions. An associated method and a computer-readable storage medium to carry a program for carrying out the method.