Wooden planter boxes offer an attractive, accessible way to bring gardening to patios, balconies, or any small space. Their raised nature allows for easier access and control over the growing environment compared to traditional in-ground planting. Successfully growing plants in these containers requires specific preparation and proper medium selection to ensure both the plants and the wood structure thrive long-term. This guide offers a step-by-step approach to preparing your wooden planter and establishing a healthy planting environment.
Preparing the Planter Box
The longevity of a wooden planter box depends on preventing constant moisture contact with the wood, making adequate drainage necessary for nearly all plants. If your box lacks holes, drill several holes approximately one-half inch in diameter across the base, spaced a few inches apart. This allows excess water to escape freely, preventing saturated conditions and root rot.
To protect the wood from soil moisture, the inside of the box should be lined. Use heavy-duty plastic sheeting or landscape fabric, secured to the interior walls using a staple gun. Ensure the liner does not extend over the top rim. If using plastic, pierce the liner directly over the drainage holes to maintain the water exit route.
For non-edible plantings, applying a plant-safe, non-toxic wood preservative or sealant (up to the liner line) can extend the box’s life. If growing edibles, choose naturally rot-resistant wood like cedar or redwood, or use a food-safe preservative like boron salts. Ensure the interior liner creates a barrier between the treated wood and the growing medium. This preparation ensures the wooden structure remains sound for many growing seasons.
Selecting and Layering the Growing Medium
For container gardening, the choice of growing medium determines plant health. Use a high-quality potting mix, also known as potting soil or container mix, which is a soilless blend designed specifically for pots. Avoid using dense garden soil or topsoil, as these materials compact quickly in a confined space. This compaction restricts air circulation and drainage necessary for healthy root growth.
A proper potting mix is lightweight and contains ingredients like peat moss, coir, pine bark, and aeration elements such as perlite or vermiculite. This composition ensures the balance of moisture retention and rapid drainage that container plants require. When filling the box, fill it entirely with the potting mix, as adding a layer of gravel or broken pottery at the bottom does not improve drainage.
This misconception is due to the “perched water table,” where water is held in the finest-textured material (the potting mix) until the capillary tension is broken. Adding a coarse layer like gravel raises the height of this saturated water layer, effectively reducing the usable, aerated soil depth for the plant roots. Therefore, fill the box entirely with the quality potting mix, leaving a small “lip” of one to two inches below the rim. This empty space prevents soil and water from washing out during irrigation.
Planting and Initial Watering
Once the container is filled with the appropriate medium, planting can begin. Carefully remove plants from their nursery containers, being mindful of the root ball. If the roots are tightly circling the soil mass, gently loosen them with your fingers or make several shallow vertical cuts down the sides of the root ball to encourage outward growth into the new potting mix.
Position the plants so the top of the root ball sits at the same level as the surrounding potting mix. The planting depth is correct when the plant’s crown—the point where the stem meets the roots—is not buried below the surface. Ensure adequate space is left between each plant to allow for their mature size, promoting air circulation and preventing competition for resources.
After placing all the plants, gently backfill any remaining gaps with potting mix and lightly tamp the soil surface to secure them. Conclude the process with a thorough initial watering—a single, deep soaking to settle the medium around the roots and eliminate air pockets. Water until it freely drains from the holes at the bottom of the planter, confirming the entire soil column is uniformly moistened for immediate establishment.