This trellis arch tunnel is stark but functional and inexpensive--and in a few months, it'll be decorative with all the plants scrambling over it! It's modular and easily expandable, but this Instructable design builds at 6 feet tall, 6 feet long, and about 2 feet wide.
(Originally featured on my blog, The Indoor Garden(er).)
Step 1: Supplies
For $90 at Home Depot, you can buy supplies to build a 6-foot-tall, 6-foot-long, 2-foot-wide trellis arch pathway--buying preconstructed trellises for that length would easily be almost $500.
Here's the list of supplies:
8 1'-long pieces of PVC (or whatever you'd like to use, really)
9 2'-long pieces of PVC
16 3'-long pieces of PVC
6 T connectors
6 X connectors
8 elbow connectors
3-foot by 50-foot fencing with 2-inch by 4-inch mesh to prevent damage to visiting wildlife that can get tangled in smaller mesh
Twine or zip ties to attach fencing (not pictured)
Step 2: Build the Backbone
Step 1 is attaching two 1-foot-long pieces to a T connector and adding elbow connectors on the ends. This will be the beginning of the top part of your trellis arch tunnel, at the entrance/exit portion. Do a second one to "close" your arch on the other end.
Step 3: Build the Backbone
Do the same using X connectors and the elbow connectors, for as many arches that you're going to use. These will be the top parts of the arch on the inside of the tunnel. (If you want to leave yourself the option of expanding, just use one of these X connector top sections at the end of your trellis arch--you can then later add another arch to extend the trellis tunnel.)
Step 4: Connect the Backbone
Stick a 2-foot piece of PVC in the first T connector, then stick that into an X connector. Keep the elbow connectors pointing down (twist them if you need to). Repeat this until you have something that looks like a flattened rib cage. This will be the top of your arch.
Step 5: The Sides
Stick a 3-foot section of PVC into the ground a couple of inches. You can anchor it with a stake if you like. Then stick on a T connector and another 3-foot section above that.
Step 6: The Sides
To get the sides of the trellis arch tunnel, add a 2-foot piece of PVC to the T connector that you just erected, then using more 3-foot PVC pieces and X connectors, build a row. Repeat on the other side of the path or wherever you're building your arch, leaving about 2 feet between the sides.
Step 7: Attach the Top
Slip the flattened-rib-cage trellis-arch top onto the tunnel sides. Take a little breather to enjoy the beauty of what you stuck together in just a few minutes.
Step 8: Finish the Fencing
Roll out your fencing and drape it over the trellis frame. Line up the edge of the fencing with the soil line on one side of the trellis and attach the fence loosely to the trellis. Snip off the fencing roll at the appropriate point on the other side of the trellis, and go to town with the twine or zip ties to tie up that fencing and make sure it will stay put. Repeat as needed until your trellis is covered in fencing for vining plants to climb.