Large rectangular planters are attractive additions to any outside living area. Redwood, cedar or teak are all good choices for planters because they will hold up well in the elements. Plans to build a rectangular planter that's long enough to border a deck or patio may be adjusted to fit your available space by altering the length or the height of the planter box. These naturally decorative rectangular planters can help delineate and separate outdoor spaces, line walkways or provide container planter spaces along a fence line.
Determine the desired size of your large rectangular planter. Plan the length of the planter box to fit the available space. A good depth for rectangular planters is 20 to 30 cm (8 to 12 inches), depending on the plants you plan to cultivate.
Measure and mark the redwood plywood to fit the length and width of each of the sides and the bottom of the planter. For example, if you're making a large rectangular planter that's 30 cm (12 inches) high, 1.8 m (6 feet) long and 30 cm (12 inches) deep, you'll need two sides that measure 30 cm (12 inches) wide by 1.8 m (6 feet) long to make the front and back panels of the planter. The plywood for the two ends of the long planter should be cut 32.5 cm (13 inches) wide by 31.3 cm (12 1/2 inches) long to create the depth of your planter. The end panels measure 2.5 cm (1 inch) larger on the width and 1.3 (1/2 inch) larger on the length to cover for the thickness of the redwood plywood. The bottom board of the large planter will measure 119 cm (47 inches) long by 28 cm (11 inches) wide so that it will fit inside the four sides of the box.
Place the bottom panel for the planter box on a flat work surface. Abut the two end panels flush against the ends of the bottom panel. The end panels should be perpendicular to the bottom panel. Attach the end panels to the bottom panel with 2.5 cm (1 inch) decking screws. Place the screws in 5 cm (2 inch) increments along the bottom edge.
Attach the front panel perpendicular to the bottom panel and the end panels. Place wood screws every 5 cm (2 inches) along the seams. Attach the back panel perpendicular to the other side of the bottom and end panels the same way.
Flip the planter box over so that the bottom is facing up. Cut the 10 cm x 10 cm (2 x 2 inch)redwood strip into 5 cm (2 inch) pieces. Each 5 cm (2 inch) section is a foot for the planter box to raise it off the ground. Place one foot in each corner of the planter box and one foot every 15 to 20 cm (6 to 8 inches) along the length of the front and back edges.
Attach the feet to the box with 6 cm (2 1/4-inch) decking screws through the centre of each foot.
Drill drainage holes across the bottom panel of the rectangular planter. Cut a section of plastic liner sheet to fit inside the long planter. Attach the plastic to the redwood with a staple gun. Puncture holes in the plastic where it lies over the drainage holes.