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Composite raised garden beds

Composite raised beds, made of plastic mixed with wood fiber, compared by the sizes, heights and soil figures their makers publish.

2bed families from Gardener's Supply, Frame It All
6published sizes and layouts
5.5 to 22 inpublished heights
7.3 to 29.3 ft³stated soil capacity

What to know first

Composite boards mix plastic with wood. Frame It All states 38% HDPE plastic and 62% wood fibers for its GardenBLOX boards, and Gardener’s Supply describes its Sustainable beds as recycled plastic and reclaimed sawdust with aluminum corners. Composite names a mixture, not one specification, so compare each maker’s own figures.

No extension service we cite publishes a lifespan for composite beds, so the warranty is the figure to compare. Frame It All gives a limited lifetime warranty if you register the bed, or five years if you do not; Gardener’s Supply’s store-wide guarantee is paid as store credit.

The beds

All raised beds
Drawn to scale from the maker’s figures: 36 in by 36 in, 10.5 in tall, 10.5 in planting depth.12243610.5 in10.5 in soil36 in × 36 in

For a composite garden bed

Gardener’s Supply Sustainable raised bed

10.5 in tall · 9.1 to 18.3 ft³ · 2 sizes and layouts

Choose a composite bed made with recycled plastic and reclaimed sawdust, held by aluminum corners. Two footprints provide a low, open-bottom growing space.

10.5 inHeight
10.5 inPlanting depth
9.1 to 18.3 ft³Stated soil capacity
Open-bottom bed2 sizes and layouts

The bottom is open to the soil below. Choose a ground location with drainage, or use a contained planter for a patio.

Drawn to scale from the maker’s figures: 48 in by 48 in, 5.5 in tall.1224365.5 in48 in × 48 in

For a square bed you can build up in stages

Frame It All GardenBLOX 4 × 4 ft composite bed

5.5 to 22 in tall · 7.3 to 29.3 ft³ · 4 sizes and layouts

A 4 × 4 ft composite bed that stacks from one to four levels. Each level adds 5.5 inches of height and 7.33 cubic feet of soil, by the maker’s figures.

5.5 to 22 inHeight
Not statedPlanting depth
7.3 to 29.3 ft³Stated soil capacity
Open-bottom bed4 sizes and layouts

Stack only the levels you need: the soil figure rises by 7.33 cubic feet with each one. The 4 × 4 ft size is nominal, so measure inside after assembly.

Build the height in stages

GardenBLOX stacks in 5.5-inch levels up to 22 inches, and each level adds 7.33 cubic feet of soil by Frame It All’s figures. The depth guide gives the soil depth most crops need, so you can stop at the height you need.

Composite or cedar?

The cedar and composite comparison sets the two side by side, and the materials guide adds metal and fabric.

References