What's inside
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A slatted porch planter gives mums and seasonal flowers room for a plastic nursery pot while keeping the pot itself out of sight. This design is a rectangular cedar frame with open sides, a slatted bottom and a removable liner. It is a manageable weekend project for a beginner with a saw and drill. Build the box to fit the pots you actually plan to use; a few minutes of measuring prevents a planter that looks right but won’t hold them.
Contents
Choose a size and layout
Measure the nursery pot at its widest point, including the rim. Add about 1 inch of clearance on each side so you can lift it out. For two common 10-inch mums, for example, a planter with inside dimensions near 22 inches long, 12 inches wide and 12 inches deep usually works. Check your pots before cutting: sizes vary, and two pots may need extra room for their rims.
The planter described here has outside dimensions of roughly 25 by 15 by 14 inches, using 1-by-4 cedar boards and 2-by-2 corner posts. Board dimensions are nominal: a “1-by-4” is typically about ¾ by 3½ inches. Adjust the cut list if your lumber differs.
Materials and tools
Use exterior-rated cedar, redwood or treated lumber. Cedar is easy to cut and naturally resists decay; treated lumber is often cheaper but can be heavier and less pleasant to work with. Avoid boards with large splits or pronounced twist, which make neat slat spacing difficult. You’ll need exterior screws, a saw, drill and driver, tape measure, square, and clamps if available. A cedar 1-by-4 board search can help you check local availability and pricing, though a nearby lumberyard may have straighter stock.
For drainage and separation from the soil, use a removable nursery pot or a plastic liner with drainage holes. A plastic planter liner is useful if you want to plant directly in the box, but it must drain freely. Don’t use an intact plastic sheet that holds water against the wood.
| Material | Best fit | Trade-off |
|---|---|---|
| Cedar or redwood | Lightweight porch planter with visible wood grain | Costs more than basic treated lumber; quality varies by board |
| Pressure-treated lumber | Low-cost build where hidden, durable framing matters | Heavier, may be damp when purchased, and can be harder to cut cleanly |
| Plastic nursery pots | Seasonal flowers you’ll swap out | Fast and tidy, but pot rims may show unless the box is sized carefully |
| Drilled liner | Planting directly in the box | Needs drainage holes and regular checks for standing water |
Cut the parts
For the approximate outside size above, cut four 2-by-2 corner posts at 14 inches. Cut four 1-by-4 boards at 25 inches for the long sides, and four at 12 inches for the short sides. These make two courses on each side, with about a ½-inch gap between courses. For the bottom, cut four 1-by-4 slats at 12 inches. Dry-fit the parts before assembly; if your boards are actually 3½ inches wide, two courses plus a ½-inch gap make a side about 7½ inches tall, not 14 inches. The posts extend above and below that box as corner legs, and the finished depth depends on the layout you choose.
For a deeper planter, add another side course and lengthen the posts. Keep the bottom slats close enough that a pot cannot sag through; a gap of ¼ to ½ inch is adequate for drainage. Sand cut edges lightly to remove splinters.
Assemble the box
Work on a flat surface. Attach one long side board to two posts, with the board ends flush to the outside faces of the posts. Predrill near the ends to reduce splitting, especially in cedar, and use two exterior screws at each end. Fit the second long board above it, leaving a consistent gap. Repeat for the other long side.
Join the sides with the short boards, screwing through each end into the corner posts. Check for square by measuring both diagonals; if they match, the frame is square. Correct a racked frame before adding the bottom. A common failure is driving screws too close to the board edge, which splits the wood or leaves a weak connection. Keep holes centered and at least ¾ inch from the end when the board allows.
Lay the four bottom slats across the frame, spaced evenly. They should rest on the lower side boards or on small interior cleats. Fasten each slat at both ends, leaving drainage gaps. If the planter will hold heavy wet soil rather than nursery pots, add a center support beneath the slats. A pot-and-water load can be surprisingly heavy; don’t rely on widely spaced slats to carry saturated soil.
Finish and drainage
Set the planter on feet, pavers or another surface that lets water escape and air reach the bottom. A box sitting flat on a damp porch can trap water and shorten its life. If using a liner, poke several ½-inch drainage holes through its bottom and confirm they drain into the gaps between slats. Don’t fill the liner with gravel as a substitute for drainage holes; water can still collect above it.
For a natural look, leave cedar unfinished and expect it to weather gray. If you want to preserve its color, apply an exterior finish labeled for outdoor wood and follow its recoat schedule. Keep finishes off plant roots and allow the coating to cure fully before adding flowers. An exterior wood sealant is optional, not a fix for poor drainage or constant contact with wet soil.
Add flowers and maintain the planter
For seasonal displays, leave flowers in their nursery pots and set them inside the box. This makes watering, deadheading and swapping out spent plants easier, and keeps damp potting mix from sitting against the wood. Check that each pot is stable and that its rim sits below the top edge for a clean appearance. Water until excess drains, then make sure it can escape instead of pooling in the planter.
Once a season, lift out the pots and clear leaves from the bottom gaps. Tighten loose screws and replace any slat that has split or softened. If the planter rocks, check the porch surface before adding shims; a rocking box can spill water and stress its joints. With drainage, modest loads and occasional checks, the slatted box should serve through many rounds of mums and other seasonal flowers.