Text and photos by Rob Danforth
This is a box bed of 4×4 posts assembled with simple overlapping corners: no complicated corners, no upright posts to drive into the ground or to nail the boards to, no metal corners or strapping, and no shelving to add to the top of the bed.
Box beds of boards are less expensive, but more complicated to build due to the outside supports for the corners and sides. Posts and supports inside an easily built bed of boards – do not actually support the boards. Soil and water pressure from within the box (or the raised bed) pushes outward. In this situation, the integrity of the box or the wood borders depends only on the galvanized nails or screws used to fasten the boards to the support posts – these support posts are not actually “supporting” the boards, they are only holding them up in a box shape. No Hockey rink has support posts on the inside of the rink. (Example: if you do not want a bear to push open your cabin door, you support the door with a dresser or a fridge against the pressure exerted by the hungry bear). Over time the fasteners will fail as the wood gets wet, and the boards will bow outwards allowing for wet soil to leak out. In addition, supports inside the box or raised bed rob you of garden space, make working the soil a little more troublesome, and provide nooks and crannies that insects and disease (e.g. earwigs and tomato blight) may inhabit.
The 4×4 posts will last a longer time than boards, will not warp as easily as boards, will provide a bit more insulation, and will make it easier to attach pots to the outside for additional growing space for food or for flowers to attract pollinators. The 4 inch wide posts also can act as a shelf for your seed packages, collector containers, and tools.
Step by step instructions: Box Bed 4 ft. x 8 ft. x 2ft 2 inches high
Tools: A saw, hammer, scissors, shovel, and a wheelbarrow
Materials:
- 21 x 8ft 4×4 posts (7 to a side and cut the last 7 in half for the ends of the box).
- 72 x 6 inch galvanized spikes @ a minimum of 12 spikes/layer. Use more if you feel the need for more strength.
- Roll of landscape fabric.
- Gravel: 12 bags of ¾ inch medium gravel.
- 2.5 cubic yards of garden soil.
1 – Lay out the geotextile or landscape fabric in a footprint slightly larger than the 4×8 bed. Note: if possible, orient the bed so that one of the long sides is facing south to give maximum sun access.
2 – Place 4 posts for the 1st level of the box – two of the 8 foot (blue) posts for the sides, and 2 of the 4 foot posts (red) for the ends. Do not place the end posts between the two side posts.
3 – Lay and spike the second layer of posts, alternating the corner overlaps. The 2nd layer will be slightly different at the corners so the corners are not identical to the first layer. See Image #3 below.
4 – Add gravel and a top layer of landscape fabric (fabric keeps the gravel from sinking into the ground soil and keeps the garden soil from sinking into the gravel). Then add some garden soil.
5 – Build and spike the following layers alternating between layer 1 and layer 2 patterns:
You may choose other woods, but Eastern White Cedar will last 10 to 15 years.
The pattern is layer 1, layer 2, and then layer 1 again, alternating until you run out of wood. Note: you can build the entire box and then add the gravel, 2nd layer of fabric, and soil or build a little, fill a little, build a little …. This way I did not have to lift all the gravel and soil to the top of the box – a wheelbarrow dumps the first loads of gravel and soil easily over the low sides of 2 or 3 layers of posts.
The gravel is for both drainage and to separate the box from the ground soil so that you do not need the ground soil tested for contaminants. It also discourages tree/shrub roots and burrowing critters from entering the box from below. A box bed is a plant paradise – nearby trees/shrubs love that and they have an uncanny ability to find it. Once they gain access, it is very difficult to remove them and they will occupy as much of the bed as they can. They did not get into my box bed, but they found my cold frame and one of my garden plots.
The geotextile or landscape fabric will keep the soil from filling and clogging the spaces in the gravel and preventing drainage.
Note: In the fall, add a minimum of 4 cm of compost and, every year thereafter in fall and mid summer, add compost or composted farm animal manure to the top, and do not rake it under. If mushroom compost is used, add less due to possible organo-chlorides which are hard on young plants and may contain an excess of nitrogen. Consider also that nature can help you compost spent plant material. In the fall, cut-and-drop the soft parts of spent plants and leave them on top of the soil.
Note the tomato support spirals and the dense planting.
Fascinators are any large and or tall plants such as tomatoes or Amaranthus planted so they shade and protect plants (south side or middle) or do not shade other plants (north side). Fillers are any low plants, both veg and flowers, that will fill in the space to control weeds and to maximize the use of space (e.g., lettuce, radish, bok choy, bush beans, herbs, …). Fallers are those vine plants that can climb out of the box and travel down to the ground (e.g., cucumbers, squash, pumpkin, …).
Tip: place sun loving fillers on the south side of the box and shelter the sun sensitive plants on the north side of the bed (e.g., lettuce and cilantro do not like strong summer sun so screen the sun with the fascinators and other plants).
A cover over the box is not essential; however, if will keep out winter impurities (wind blown salt or ice melter, snow mould) and it will keep off the rain and snow melt which will wash away the water-soluble plant nutrients that you want to keep near the surface of the bed. In the fall you may have added the 4 cm plus of compost that is recommended as well as the cut-and-dropped soft parts of spent plants which will add to the natural composting process – and which will have all but disappeared come spring – mine do! With a cover, the reclaimed water-soluble plant nutrients will remain near the top of the bed and will not have been leached away by water.