How to Build a DIY Planter Box

Tags: patio, deck

Family assembling wooden planter box in backyard

Planter boxes for flowers and other plants are great ways to accent your patio, porch, deck, yard and other outdoor spaces. They complement existing landscape features to help make everything in your yard work together as an attractive and relaxing place.

Before You Begin

There are as many shapes and sizes of planters as there are plants. They can be large enough for small trees and small enough for a windowsill herb or flower garden. Use window planters, trellises and rectangular planter boxes to add beautiful accents to your outdoor décor.

Put some thought into where you'd like to put your planter and how it will work with your existing design; then decide what kind of plants you want.

Now, roll up your sleeves and let's get started.

Build a Rectangular Planter Box

This kind of planter is practical for most types of plantings. Because it will be outdoors you must use wood and materials that can withstand the elements. Cedar, redwood and treated lumber are good choices because they are naturally weather resistant. As long as the wood is treated with some kind of waterproofing your planter should last for years.

Step 1: Start Cutting

Use a circular saw to cut 2x4s into eight 20" L pieces, six 18" L pieces and sixteen 17" L pieces. Cut 2x2s into four 18" L pieces. Next, use a miter saw to cut two 21-1/2" L pieces and two 24-1/2" L pieces with the ends cut at a 45-degree angle.

Always wear goggles or safety glasses when working with a saw.

Step 2: Assemble the Sides

Put two of the 18" L 2x4s and four of the 17" L 2x4s directly beside each other on the ground, making sure the top edges of the boards are flush with each other. The 18" pieces should be on each side of the four 17" pieces. Lay one of the 20" L 2x2s on top of the 2x4s on its short side (perpendicular), centered, and make it flush with the top edge. Using a power screwdriver, drive wood screws through the 2x2 into all of the 2x4s.

Put another 2x2 on the bottom edge of the 2x4s and repeat the same process, so that there is a top and bottom 2x2 piece.

Repeat this process three more times, until you have four sides.

Step 3: Connect the Sides

Place the edge of one of the sides against the inside face of another side piece. Make the edges flush and use a square to fix the corner at 90 degrees. Drill four screws through the outside face into the edge of the other. Drive two more screws through the other side's face into the 2x2s on the back of the first side.

Do this for the other two sides. Make sure that the 2x2s are on the inside. You should now have a rectangular box with four legs.

Step 4: Assemble the Bottom and Top

Bottom-up view of assembled planter with base — Bottom view of assembled planter with bottom boards resting on interior 2x2 supports

Assembled planter top view — Top view of assembled planter with frame resting on planter walls

Place the 18" 2x4 pieces into the box, resting them on the lower 2x2 piece. Screw these 2x4 pieces into the 2x2s on both ends.

Lay the remaining 2x4 pieces with mitered ends as a frame on top of the box. Drive two screws through each end of the 2x4s into the box frame to secure them to the top.

Tapered, Outdoor Window Planter

You'll get the best results by making your outdoor window box as wide as your window frame. The planter should be at least deep enough and high enough to accommodate a 6" diameter flowerpot. We suggest you use 1" cedar, redwood, or treated lumber because they are resistant to weather and insects. Add waterproof sealant to the wood for extra protection.

Step 1: Cut the Wood

Cut the pieces for the front, back and ends from 1" x 8" boards. Use a circular saw or table saw when cutting the pieces for your planter.

For the front and back, cut or plane a 5-degree bevel along the bottom edge of each piece.

To make the ends, cut two pieces of 1" x 8" wood to be 6" wide. This will correspond to the height of the end. Then cut the sides of these pieces at an 85 degree angle to create a 5'' and a 7'' base on these two trapezoidal pieces.

To create the bottom, set the saw's bevel adjustment to 5 degrees, and cut a piece of 1'' x 6'' so that it is 5" wide. Use a plane to bevel a 5 degree angle on the two lengthwise edges. Next, cut the bottom piece 3/4" shorter than the length of the front and back pieces so it will be recessed 3/8'' and fit properly with the front and back when assembled.

When using a circular saw, be sure to wear protective eyewear and wear a facemask to prevent you from inhaling sawdust.

Step 2: Assemble the Planter

Using a small brush with a 1/2'' tip, apply waterproof wood glue on all edges of the bottom and rest it on 1/2'' thick spacers. Clamp the two ends onto the bottom and pre-drill 3/32'' pilot holes for the fasteners. Secure the ends to the bottom with 6d-galvanized nails.

Glue the front and back edges of the end pieces. Similarly clamp and attach the faces to the bottom and the ends. Wipe off excess glue with a damp cloth.

Pre-drilling prevents the fasteners from splitting the wood and makes it a lot easier to accurately drive nails or finishing screws.

Step 3: Seal It

At the very least, you should waterproof the inside of the planter. Mask the top edges of the planter with masking tape and apply a synthetic rubber coating to the interior surfaces. Synthetic rubber coating is available in spray cans or as a brush-on liquid and will form a flexible, waterproof surface when it dries.

Step 4: Mount the Planter

Once you've put the planter together, it's time to mount it. Drill two 1/2"-diameter holes into the planter about a ¼" of the way in from the ends and 1-1/2" below the top. Hold the planter in position under the window where you're mounting it and hammer a 3/8" hanger bolt through each hole, slightly into the exterior surface of your house to mark it, or use another method to mark where the holes should be. Drill two ½" pilot holes at the marks and then hammer in the hanger bolts, leaving about 2" of each bolt sticking out. Hang the box on the bolts and put a 3/8" washer and nut on the end of each bolt.

Build a Trellis

Vegetable trellises maximize your garden space, as well as your crop or bloom. Vertical growing allows you to grow two or more plants in the same space and exposes them to more sunlight and oxygen, which means less rot and mold. Because they're not embedded in soil, trellis-grown plants are easier to pluck.

Step 1: Pick a Spot

Before you build your trellis you have to decide where you're going to put it. If you're going to plant it near other plants or flowers, position the trellis so that it won't cast shadows on them. The ground should be flat and level without any rocks or debris within two feet of the surface.

Step 2: Plant a Post

Use a shovel to dig two 24" holes 10' apart. Use a mallet and drive a wooden fence post deeply into each hole. Cover both of their bases with dirt.

Use wooden stakes to give your trellis more support. Drive each stake into the ground, angling it toward the foot of each post.

Step 3: Install Wire

Wire is used as the trellis' skeleton, supporting the plastic netting that will, in turn, support your plants as they climb. To attach the wire, wrap it tightly around one stake, then back up to the top of the post. Staple it securely at the top using a staple gun. Then run the wire over to the other fence post, wrap it around the post and staple it there. From there, run it back down to the other stake and tie it tightly.

Your knots must be very tight to make sure the trellis stays solid and steady. Get a firm grip with a pair of pliers.

Step 4: Hang Netting

As you hang your netting, start by spacing S-hooks every 12" to 15" across the wire between the posts. Hang the plastic netting from the hooks, just like you'd hang a shower curtain. Staple the netting to each post with your staple gun, keeping it taut as you go. Move downwards, stapling every 2" to 3" until you reach the bottom of each post.

That's it! You're ready to plant. Enjoy your new planters and trellis.

That's it! You're ready to plant.