When you order a planter box from our factory, one of the first questions you might ask is: how deep are the planting wells? The answer matters greatly if you hope to grow root vegetables like carrots, radishes, beets, turnips, or parsnips. Unlike shallow-rooted herbs or leafy greens, root crops need sufficient vertical soil space to form full, healthy underground structures. So let’s get straight to the numbers and the practical details.
Our standard planter boxes feature planting wells with a depth of 12 inches (30 cm) for the medium size and 18 inches (46 cm) for the large size. The extra-deep model goes down to 24 inches (61 cm). These measurements refer to the usable soil depth inside the liner or well, not just the outer frame height. We design the wells to be open at the bottom for ground contact, but if you use the optional plug kit, you can convert them into closed-bottom planters with the same internal depth. For closed-bottom use, we add a drainage layer of 1.5 inches, which slightly reduces the soil area — meaning your actual growing depth is about 10.5 inches, 16.5 inches, or 22.5 inches, respectively.
Can you grow root vegetables in these depths? Yes, with some guidance. Short and round varieties such as ‘Paris Market’ carrots, ‘Cherry Belle’ radishes, and ‘Detroit Dark Red’ beets will thrive in the 12-inch wells, as they only need 6 to 10 inches. Intermediate carrots like ‘Danvers’ and ‘Nantes’ grow beautifully in the 18-inch option, which is also ideal for turnips and kohlrabi. For long daikon radishes, large parsnips, and main-crop storage carrots, choose the 24-inch model to avoid any root bending or forking. If you plan to grow very long taproot varieties like ‘Imperator’ carrots, even 24 inches may not be enough — those need 30 to 36 inches of loose soil. In that case, we recommend our custom deep planter line, which can be specified up to 36 inches deep.
Beyond depth, what else should you know about our planting wells? First, the walls are slightly tapered — about 2 degrees — which makes it easier to remove root vegetables without snapping them. Second, the interior is coated with a food-safe, non-toxic sealant that resists moisture and prevents soil nutrients from leeching into the frame material. Third, we offer an optional mesh bottom that stops burrowing pests while still allowing drainage. Fourth, the soil volume per well is generous: a 12 by 12 by 12 inch well holds roughly 1.1 cubic feet of soil, while an 18 by 18 by 18 inch well holds about 3.4 cubic feet. That volume gives roots plenty of loose material to push through, provided you fill it with well-aerated potting mix rather than heavy garden soil.
One thing we always tell customers: depth is not the only factor. Root vegetables dislike compacted soil. Even with a deep well, if you pack the soil tightly or water too aggressively, roots will struggle. We recommend a loose mix of compost, coconut coir, and perlite in a 2:1:1 ratio. Also, maintain consistent moisture, as alternating dry and wet conditions causes cracking and woody texture. Our planter boxes come with a drip irrigation channel along the rim that allows slow, even watering, which helps prevent the soil surface from crusting over.
Let me also address a common misconception. Some people assume that a tall outer frame always means deep wells. That is not the case in many mass-produced planters, which often have false bottoms or decorative skirts. In our factory, the frame height equals the well depth — there is no spacer, no false bottom, and no wasted space. You can verify this by measuring the inside vertical distance from the rim to the floor grid. We publish these specs on every product page, and we invite you to measure the wells upon delivery to confirm the depth.
To sum up: our planter box factory offers planting wells of 12, 18, or 24 inches as standard, with custom depths up to 36 inches. If you want to grow root vegetables, choose the depth based on the mature size of the crop. Short roots fit in 12 inches, medium roots in 18 inches, and long roots in 24 inches or more. With the right depth and proper soil care, you will be pulling out straight, crisp, beautiful root vegetables from your planter box all season long.
