Monday, August 3, 2015

Using Electric Fences to keep garden pests away
by Garret K
Early in the garden season of 2015, squirrels seemed to be eating everything I planted. My first plantings of beans, peas, corn, zucchini and cucumbers were lost to these pests. I knew the plants would have been much further along had they been able to grow undisturbed, and I'd would have been spared the extra time and costs of resowing seeds had I put up an effective barrier. Therefore, I decided to team up with Kaven, who owns the plot next to me, and put up a small electric fence. An electric fence, for me was a simple choice as I come from a farming background, and have experience setting up and using these fences. Also, setup of it would be aided by the fact that I am able to use the hardware from the farm to set up my fence in the community garden. So the overall cost, split by Kaven and I, was the cost of a few posts and a couple additional plastic pieces; about $20. For those interested in installing a fence themselves, the real expense is the electrical unit (approx. $100) and the battery (approx. $50) to run it. This cost may vary, as new units can run off of built-in solar panels. I actually hope to use these solar units in the future as they are more sustainable and environmentally friendly.

Remembering back to your high school physics course, you might recall that electricity travels from the positive (+) connection to the negative connection (-). A basic electric fence with only one wire sends out a small positive charge across the wire and connects it's negative, or ground wire, to the ground. When the wire is touched, the circuit is completed and a shock is administered through the object touching the wire, through the ground and back to the unit. It feels similar to a static shock. Actually, if nothing is touching the wire (no leaves, plants, weeds, etc. that offer some resistance and decrease the shock voltage) then the maximum voltage of the unit would be 13,500 volts. This can be similar to or lower than a shock one gets from static cling. A static shock ranges between 4000 volts and 35,000 volts. Wearing cotton under a wool sweater is therefore more dangerous than the fence.

Since a garden fence needs to deter squirrels, who can jump, I knew that one wire wouldn't be enough, and that the fence needed to be higher. I also knew, that if the squirrel jumped into the fence, it won't receive a shock unless it was touching the ground - just like birds on the electric wires. So I needed to design a fence that was both tall and that could administer an electrical shock without needing a pest to be touching the ground. The solution to both these problems was to alternate positive and negative wires on the fence, as in the illustration below.  A leaping intruder would receive a shock as long as it touched both the positive and negative wires.
Schematic of the electrical fence designed for use in Sandy Hill Community Garden
So far the electric fence has been successful. The squirrels seem to be repelled by it, that is until they take to jumping onto the tall corn stalks to avoid the fence.  And the ground hogs, that have been making an appearance these past weeks with a ferocious appetite, seem to be scared away too. In fact the success of our plot is all the more obvious when we look at plots to the left and right of our plot and notice the devastation. For example, a fellow gardener Chris lost the better portion of his garden, his mesclun lettuce, kale, chard, and broccoli despite his small chicken wire fence. 
In summary, Kaven and I managed to emerge relatively unscathed the groundhogs and the squirrels since we installed our electric fence. While we've watched squirrels scaling chicken wire, a common garden fence used in our community garden, they seem to be repelled from our fence.  So, with the encouragement and enthusiasm of my fellow gardeners I am writing this blog to share my experience with electric fences for pest control. Thanks for reading,  happy gardening and feel free to ask questions in the comments!
Harvested produce from my plot

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