On average, plantar warts and palmer warts are small, about the size of a pencil eraser. But some warts grow bigger. Sometimes plantar warts can grow in clusters; those are called mosaic warts. Sometimes corns or calluses are mistaken for a palmer or plantar wart. In some warts, little black dots appear, leading people to call them "seed" warts. Actually the black dots are little blood vessels that have grown up into the wart. Warts don’t really have “seeds.” Plantar warts usually don't stick up above the skin as much as warts on the hand, partly because of the pressure of walking and its flattening effect.