Abstract: A high-speed transplanter is described for mechanical transplanting of seedlings in grow blocks formed into easily handled modules. The transplanter includes cutting blades for separating the modules into files, delivery tubes for downwardly moving the files into spaced-apart positions above furrows, wheels for pulling off individual blocks and placing them at zero ground speed within the furrows, and an assembly for detecting dud blocks (having no seedling) and advancing a file by an extra block length to provide a seedling block for the wheels. This system depends on the probability that finding two non-germinated seeds in consecutively linear sequence is much lower than the percentage of non-germinated seeds within a pattern of randomly distributed seeds.