GROW GIANT PARSNIPS - Gerald Stratford grows giant parsnips in PVC tubes. We're talking 2 feet long, straight as an arrow. Here's why it works. Parsnips are taproots. They send one main root straight down hunting for water. In a normal bed, that root hits rocks or packed clay within a few inches and either forks, twists, or quits. The PVC tube removes every obstacle. Loose soil all the way down, steady moisture, zero resistance. The root follows the tube like a highway and focuses all its energy