For several years now I have been building fence boxes for my raised-bed garden boxes using PVC tubing and fittings, covering them with poultry mesh to keep out my dogs, the rabbits, in some cases, squirrels, raccoon, and other assorted pests. These can also be covered in plastic to extend the growing season.
My first experiment was with mini hoop houses. These are good for medium height plants that need to be fully enclosed; such as Brussels sprouts. Depending on your purpose, they can be covered in poultry mesh, bird mesh, insect netting, or plastic sheeting … or a combination of these.
The shape makes them fairly easy to move on and off the beds yet, if covered in plastic, they shed snow well.
The drawback to this shape is the amount of tension built into the frame. This tends to pull the joints apart around the bottom unless the connectors are glued together. You can assemble the frame, then drill through joints to insert a small sheet metal screw to hold the joints firm, but these screws rust quickly unless you use brass or stainless steel.
This is the design I use in most of my boxes. They are simple to construct, very easy to move on and off the boxes, and are effective at keeping rabbits and most of my dogs out. I could add a square of 48-inch mesh to the tops to keep everything out, but I don't need this. At least, I haven't needed this yet.
This is a modification of the box frame model to add a house style roof. This is great for taller winter crops like rosemary and Brussels sprouts. Sprouts don't need protection from mild winter weather, but covering these boxes in insect mesh keeps the cabbage worms out of them.
The main drawback is that they are harder to move on and off – at least for a short guy like me. If you're a Jolly Green Giant, that would not be an issue.
The other issue with these is the more complex construction; especially the corners. There may be a better way to do this, but I use a tee in the side and two 90 degree elbows with short pieces (1-1/2 inches) of tubing as connectors. If I don't glue them together, the top easily comes off so the box can be used as a more handy square box in the summer. Just be sure to turn the tees down to keep rain out.
Some of my veggies require a trellis to grow on. Trying to mount a trellis inside a square box proves problematic because you can't lift the box off to get in and weed. Instead I build a square box with a trellis as one side. I have several heights for different uses. But again, getting in to plant and weed is a problem if the box is all connected together.
So I build a 3-sided box to go with the trellis back. Bungee cords, zip ties, string, or wire can be used to fasten the “arms” to the trellis to add a bit more support if you want.
The secret to most of these designs is this specialty fitting called a 90 degree angle with side-port. I do not know if it is an actual plumbing fitting – I've never encountered one in remodeling any plumbing – but it is very handy for making square corners on a box.
If you plan to cover the boxes with plastic, windy weather can lift any of these designs out of the garden box and send them rolling around your yard (and the neighbors yard, and the neighborhood). I've tried two methods to fasten the fence boxes to the bed boxes.
First I set the bed up as it was going to be used, marked the level of the top of the bed box on the PVC upright with a Sharpie, then drilled a hole through the bed box and the PVC upright. Slipping a framing nail through this hole locks the fence box to the bed box. Doing this at two diagonally opposing corners is usually sufficient. It has been beneficial to drill the hole in the wood (but not the plastic) with a larger bit because the wood swells and tends to lock the nail in place. Also, don't push the nail all the way in, leave it sticking out a bit so you can get a grip on it. And identify the two corners so you get the cover back on the box the same way each time.
The second way is much easier. Just drive a roofing nail into the middle of two opposing sides of the bed box – leaving them sticking out 1/4 inch. Then using some light cord or heavy string, make a loop in one end. A sheet bend is a great knot for this because it doesn't slip: you want the loop to stay a loop. Put the loop on one nail. Run the cord over the top of the box to the other nail and tie the cord securely to that one. Cut off any excess.
Slip the loop off the nail to remove the box, put it back and the cord holds the box down when it's windy. If you have a lot of really windy days, you might want to use two tie-down cords.
One major thing I've learned that effects ALL configurations is to use zip-ties instead of bailing wire to attach mesh to the frames. Bailing wire rusts quickly making ugly brown stains on the PVC, and the twisted stubs do rotate around and poke out to snag and tear my clothing and skin. Our local dollar store has packages of 100, 7 inch long, white zip ties for just a couple of bucks. These are easy to use and cost effective (compared to buying them at a hardware store).
Another lesson learned is to size things so the galvanized poultry mesh attaches to the top of the bottom rail and is lifted clear of the dirt as much as possible. Wire mesh that sits on moist dirt rusts through very quickly. Also, if covering any shape of fence frame in a combination of wire mesh and plastic, hang the mesh between the PVC members and fasten the plastic to the outside with duct tape. This creates an air gap between mesh and plastic. If the plastic sheeting lays on top of the mesh, the mesh rusts through quickly because of the condensation that collects inside the plastic.
That's a quick update on my PVC framed garden fence box experiment. If you have any suggestions, feel free to add them in the comments below. Thanks for reading!