Building your own large outdoor planter saves money and gives you complete control over size, material, and style for your specific space.
Whether you need a tall planter to frame an entryway or a long box for a deck railing, building it yourself is straightforward with the right approach. The key decisions come down to three things: material (wood or cement), drainage, and weather protection. Here’s what you need to know to build a planter that lasts through the seasons.
Wood vs. Concrete Planters: Which Material To Choose
Wood planters are lighter, cheaper, and easier to build, while concrete planters are heavier, more permanent, and better suited for uncovered outdoor spaces. Each has specific build requirements.
Wood planters work well for most settings. Standard construction uses treated lumber or cedar, with 2×2 frame supports and 3-inch exterior screws. The build sequence is: measure your space, create a cut list for the frame and slats, cut all pieces, assemble square frames using a set square to keep joints true, add slats or boards, then drill drainage holes in the base. For drainage, a medium planter needs about six half-inch holes spaced evenly.
Concrete or cement planters suit uncovered, fully exposed locations. The process involves mixing cement, applying it in layers to a mold (letting each layer dry about 24 hours before the next), curing for 24 to 48 hours, then demolding, sanding, and sealing. Jenna Sue Design’s method for fluted cement planters uses flexible trim for the top edge and microcement applied in coats, sanded after 12–24 hours, finished with a matte sealant for outdoor use.
Drainage and Weather Protection Are Non‑Negotiable
Every outdoor planter needs two things: a way for water to escape and a barrier between the soil and the structure. Skipping either guarantees a short lifespan.
Drainage: Drill or space holes in the base according to the planter size. Alternatively, leave gaps between base slats on a wooden planter.
Weather protection: Line wood planters with plastic sheeting or landscape fabric, secured with a staple gun, before adding gravel and soil. For uncovered wood, apply paint, stain, or sealant to protect from moisture. My Creative Days notes that pallet wood specifically needs paint or stain “to protect it from the elements.” For uncovered concrete planters, a matte sealant is essential — Jenna Sue Design states that uncovered outdoor planters “will want to protect the finish with a matte sealant.”
Common Build Mistakes To Avoid
Three errors account for most planter failures: poor drainage, an unlevel base, and wrong plant choices. Avoid these and your build will outlast the season.
- Skipping drainage: Without escape holes, root rot kills plants and water damage rots the planter. Always include drainage, even if covering the bottom with gravel.
- Omitting pilot holes: Driving screws near board edges without pilot holes splits the wood and weakens the joint. Drill them — it takes seconds.
- Choosing plants that don’t match the site: Mom Can Do Anything emphasizes picking plants based on climate, sunlight, and soil conditions. A shade‑loving fern won’t thrive in a full‑sun planter on a south‑facing deck.
If you’d rather skip the build and buy a ready‑made solution that handles the hard part, our tested roundup of large planters for outdoors covers the commercial options that hold up year after year.
Setting Up and Planting Your Finished Planter
Once the structure is built, proper placement and planting determine whether your effort pays off. The planter should sit on a level surface — Claire Douglas Styling and Mom Can Do Anything both emphasize leveling the base for stability. Inside the planter, layer in order: a few inches of gravel or stone for drainage, landscape fabric to keep soil from washing through, then quality potting mix matched to your plants. From House to Home’s method uses Styrofoam pieces inside the frame to reduce soil volume in deep planters, topped with a final soil layer for the root zone.
The soil you use matters: potting mix drains better than garden soil and won’t compact as quickly. For large planters, filling the entire depth with soil gets expensive and heavy — filler material at the bottom (Styrofoam, crushed cans, or large stones) reduces both cost and weight while still allowing drainage.
FAQs
How many drainage holes does a large planter need?
The exact number depends on the planter’s footprint — wider bases need more holes to prevent water from pooling far from any exit point.
Can I leave a wood planter unsealed?
You can, but it won’t last. Untreated wood exposed to rain and sun will rot, warp, or crack within a year or two. Exterior paint, stain, or a clear wood sealant adds years to its life. Lining the interior with plastic also protects the wood from constant soil moisture.
What’s the best wood for an outdoor planter?
Cedar and redwood are naturally rot‑resistant and don’t need chemical treatment, making them good choices for vegetable beds. Pressure‑treated pine is cheaper and durable, though some avoid it for edible plants. Avoid standard pine or fir unless you seal or paint the entire piece.
References & Sources
- B&Q. “How to Build a Wooden Planter” Official DIY guidance covering build steps, pilot holes, and drainage hole sizes.