The standard boxes from our planter box factory are 12 inches deep, measured from the inside floor to the top rim. When filled to the recommended level, they provide roughly 12 inches of usable soil depth. The short answer is yes—12 inches is enough for many root vegetables, but it is not ideal for every long-rooted variety.

For radishes, scallions, beets, turnips, and compact or round carrot varieties, a 12-inch box gives roots plenty of room. These crops also benefit from loose, stone-free soil, steady moisture, and good drainage. If you plan to grow full-size Nantes or Imperator carrots, long parsnips, or large daikon, choose a deeper 15–18 inch model from our planter box factory instead.

Depth alone does not guarantee success. Root vegetables need soil that is easy to push through, so mix topsoil with compost and a little sand or coco coir if your mix is heavy. Avoid compacting the soil, keep it evenly moist, and add mulch to prevent crusting. Drainage holes and raised feet help protect deep roots from waterlogged conditions.

When comparing planter boxes, measure the inside depth, not the outside height. Also allow 1–2 inches of freeboard so water does not spill over. If you add a drainage layer, do not count it as soil depth; choose a deeper box or use a wicking system. With the right depth and soil, standard 12-inch boxes can produce excellent radishes, beets, turnips, and short carrots, while deep boxes are the better choice for long root crops.