How to Turn an Existing Planter into a Square Foot Garden

Since I moved into my house almost two years ago, I’ve wanted to build a Square Foot Garden. But first I needed a place to put it. I have several existing planters, but two of them are too low for a SFG. One holds our barbecue, a rose bush, some bulbs, and a potato bush that I rather like. (Note: a potato bush is in no way related to potatoes.)

I did have a very large, triangular raised brick planter filled with a shrub I hated. My first thought was to rip out the shrubs, take a sledgehammer to the bricks, and put a couple of traditional Square Foot Garden beds in its place. But several people, including my husband, suggested that I use the existing planter instead, so I made my own version of an SFG. If you have a planter, you too can plant an SFG without taking additional space or building boxes. Here’s what I did:

  1. Remove the shrubs or hire someone to remove them. This is what the box looked like before. We asked the gardeners to cut down the shrubs and pull out the roots.
  2. Make a map. I drew the plan on graph paper I printed off the internet. Since my planter is 10 feet by 8 feet by 16 feet instead of 4 by 4 feet, I had to make a path. I roughed out a few potential paths and finally settled on one design.
  3. Lay bricks, stones, or gravel on the path. I didn’t bother to lay my bricks on sand and fill it in, like you’re supposed to, because this first year was an experiment. I also used a mix of old bricks my dad gave me and new bricks I bought.
  4. Dig out the existing dirt. We used some of it in the new planter, but most of it went onto our hill to try to snuff out some weeds. I didn’t dig out under the bricks because nothing grows under the path (except weeds).
  5. Mix new dirt. If you read the book, you’ll find the recipe for Mel’s Mix: 1/3 vermiculite, 1/3 peat moss or coir fiber, and 1/3 blended compost. (Calculate your needs by the cubic foot.) I used E.B. Stone’s compost, or you can buy five different kinds of compost to get a balanced mix. If you make your own compost, then it should be well-balanced already. My old dirt was primarily sand, so I used some of that, too.
  6. Fill the box with the new dirt. Wet it down. Fill again.
  7. Buy 8 foot strips of lath and a box of lath screws. Look in the gardening department for the lath – I found it in the back of the Home Depot garden area. The people in the lumber area had no idea what I was talking about.
  8. Lay out grids in the box. Because I was creating my own layout, I made each box exactly 12 inches across. The result shifted my graph paper plan slightly, but it looks good and each box is a good size. To cut the lath, I laid it in the planter, then drew a cut line so it would fit just against the edge of the box. A hand saw was all I needed to cut it. I needed a drill to get the screws in, but it went quick. When I needed to connect sections, I screwed three pieces together.
  9. Add a trellis (optional). I propped the six-foot tall tomato cage I broke open last year in the back of the box, then tied it to my fence. I supported the open edge with an extra piece of lath. I’ll use this to vine my tomatoes and peppers.
  10. Plant. I may add bubblers or a drip system at some point, but I’m still deciding about that.

So far I’ve planted tomatoes, onions, and peppers. I also put in germinated seeds for carrots, lettuce, sage, basil, oregano, chives, scallions, and parsley, but we had a heat wave and the soil wouldn’t stay moist. I’m still working on a square covering system to maintain moisture. Since we’re already in May, I’m buying seedlings this weekend rather than attempting more seeds. I’m also growing mint and rosemary, but they go in separate pots. Do not put them in your regular garden. My strawberries are in a strawberry pot so I can roll it around the yard to produce different levels of shade.

The total time for this project was about two days – one to shop for bricks and lath, and one to lay the bricks, dig out the dirt, fill it in, and lay the lath. I dug out the dirt by myself, but my best friend helped me fill it back in.

The total cost for this project was about $120, but most of it was a one-time expense. I will buy some row cover coil, for about $30, and clear plastic sheeting for another $5 to create plot covers.

Next year, my only costs will be a new path if I opt to get something nicer than the bricks and more plants. I’m making compost, so I won’t have to buy more dirt.

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