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Building (and Growing in) Potato Cages
We love Potatoes. However, the traditional methods of growing them underground simply would not work here. The ground here is a mix of sand and clay. The first 8-12" is very hard packed and void of nutrients. We have to make all the soil we grow in via mulching or amending. The first year here we discovered potato bags. We still use them on the decks. This year we constructed four potato cages - basically larger version of potato bags with the benefit of making it much easier to harvest.
Following the directions below will produce a circular potato cage approximately 3' in diameter and 28" tall. One cage will allow you to grow a fair number of potatoes as they will grow in layer upon layer as you add more and more soil during a season.
Step 1: Cut and Mark the Garden Fence
For our cages, we used 28" tall garden fence. You could use 24" as well but 36" is too tall as you have to be able to bend over it and reach the ground on the inside. First you want to cut the fence at 10 feet in length. You can use the side cutter on linesman pliers, bolt cutters or my favorite, a side grinder with a metal cut-off wheel.
You want to cut the horizontal strands close to the vertical strand - don't split the difference between the verticals. IMPORTANT: You want one end of the fence closed (where the end row of squares still forms a box) and the other end open where you have 5-6" loose ends of horizontal strands instead of closed boxes. You will use the loose strands of one end to lace through the closed boxes of the other end to hold the fence together.
Since you will use three posts to support the fence circle, but want to be able to open it up at the end of the season, you need to mark where the posts will go. Using any type of tape or string, you will want to mark the top edge of the fence from the boxed end at 20", 60" and 100" (or 20" in from each end and in the middle at 60"). This will put one post every 40" with the laced opening split between two posts.
Step 2: Form the Circle and Lace Together
At this point you are ready to make the three foot diameter circle. Let the 10' piece of fence curl the way it wants to and bring the ends together. Thread each loose horizontal strand through the matching closed box of the opposite end. Pull the strand all the way through and bend it back around and wrap it once on itself to make it secure. You don't need to get over zealous here because at the end of the season you will be unlacing the seam to allow the potatoes and soil to fall out. NOTE: don't worry if the finished circle isn't exactly round - you can adjust that when you drive the posts into the ground.
Step 3: Insert and Secure Posts
You can use any sturdy post for these cages. The cage itself is self-supporting - it won't collapse - but needs the posts to maintain its shape and stay in place. You can use 4' T-posts, 40" lengths of 1/2 or 3/4" electrical medal tubing (EMT), or re-bar. For the sample in the photos, I had some 3/8" diameter re-bar laying around so I took a 10' stick and used a side-grinder to cut it into three 40" pieces.
The advantage to using re-bar or EMT is you can lace it vertically into the fence without having to use wire, tie-wraps or similar to hold the fence to the post. You want to insert or drive the posts where you marked the fence at the 40" intervals. If you use T-posts, drive them on the outside of the fence and use bailing wire or tie-wraps to secure the fence to the posts. Do the best you can to form a round circle when placing the cage - but it's not critical - pretty much any shape will be fine.
Step 4: Line the Cage with Weed Barrier
You will need 11' lineal feet of 3' tall weed barrier. Weed barrier will hold in the soil while allowing the excess moisture out. Assuming you used 24" - 30" tall garden fence, drape 3"-4" of weed barrier over the top of the fence starting at the laced seam. Follow the circle around securing the weed barrier every foot or so with tie-wraps (just punch a hole through the barrier) or binder clips. We found a big box of binder clips (100's) at a garage sale and use them often.
If all goes correctly you will end up with about a foot overlap of barrier when you complete the circle. Smooth the barrier down the inside of the fence and spread the extra toward the center to hold the soil.
Step 5: Add First Layer of Soil and Plant
Add 4"-5" of good soil into the cage and plant your seed potatoes. As the greens grow 6"-8" above the soil line, add 3" -5" more soil. Repeat this process as many times as you wish. The potato plants will sprout new potatoes into every layer of soil. It won't take long before the plants will be shooting out the top of your cage.
Step 6: Unlace and Harvest
This is the beauty to using potato cages. At the end of the season (when the green parts of the plants start to die off), you simply unlace the wire cage, pull the weed barrier apart and gently start pulling all the soil and taters out. It sure beats digging in the hard ground and you can produce a lot more potatoes per square foot due to layering.
If you don't want to build potato cages, you can use potato bags (pictured below). We still use them on our deck but the cages produce 2 - 3 times the crop.