Will Copper Pipe Harm Plants?

Some people seem to think that copper pipe will harm plants in various ways: by the plant touching the copper pipe, by copper leaching into the soil and poisoning the plant, or by the pipe getting too hot or cold. As far as I can tell, most of this misinformation is passed around by people who have never grown a plant on a copper trellis.

I am not a chemist, biologist, or any other kind of scientist, so I can't give "technical" answers to these concerns. I have some experience growing plants on copper trellises though, and this is my experience:

• Plants don't grow any differently on a copper trellis than they do on a wood trellis, a galvanized steel support, a vinyl support, a wood fence, or a brick wall. Leaves and stems don't die or develop any kind of problem just because they are in contact with copper pipe.
• Copper trellises with some pipe underground do not "poison the soil" as far as I can tell. The plants I have grown grow just fine. If this is a concern to you, you can wrap the part of the pipe that will be underground with some plastic shipping tape, available at any office supply store. The tape is made from mylar and should prevent any contact between copper pipe and soil.
• Copper pipe is an extremely good conductor of heat and cold. This means the pipe stays approximately the same temperature as the air. Your plants are already at the temperature of the air, so it makes no difference if they are touching copper pipe that is also at air temperature. Copper pipe does not "soak up heat" all by itself. You can test this by touching a copper trellis in full sun on a hot day. The trellis will probably just feel lukewarm. On the other hand, a few people have told me that they designed a trellis that will support a plant and also be used as a plumbing system to deliver water for irrigation. Water kept within a copper pipe would retain heat (just like your garden hose left out in the sun), and could make the trellis quite hot.

How do I keep my trellises bright and shiny?

1. First, be sure you really want a bright shiny trellis. If you just clean the trellis after you make it and then leave the trellis alone, it will turn a handsome (my opinion) uniform brown color and stay that way without any work. Maintaining a bright shiny appearance will require maintenance. The maintenance requires that you clean the trellis, and how are you going to clean the trellis with plants growing on the trellis?
2. Second, clean the completed trellis with steel wool as explained on this page.
3. Third, apply a paste wax or polymer finish made for waxing your car. Just like your car, the finish will need to be renewed every few months in order to keep the trellis looking bright.
4. Alternatively, you can apply a clear spray acrylic or lacquer finish designed for exterior applications. After it cures, apply paste wax or other automotive finish.

How do I give my trellises a green patina?

Various chemicals can cause copper to turn a green color. This color is called a "patina". Copper can also develop this patina naturally over a period of many years of outdoor exposure. If you live near the ocean, the salty air may cause the patina to develop more quickly.

The first step in applying a patina is to clean the copper down to bright shiny metal. The patina chemicals need to act on fresh copper, not copper that has a coating of oxidation or flux residue.

• Some art supply or art and craft stores sell "patina" chemicals that will act on copper to turn it green. You can search the web for "patina chemicals" or "patina finishes" to find them. Some of your local art or craft stores may also carry patina chemicals. This is the safest, quickest, but most expensive technique.
• A dilute hydrochloric acid usually called "muriatic acid" will turn copper green. The acid needs to stay on the copper for a while, such as by soaking overnight or sponging it on every hour or so for a couple days. Muriatic acid is dangerous stuff and you must follow all safety precautions on the label - working outdoors, protecting skin, eyes, and clothing, and not breathing the vapors. Muriatic acid is sold at most home centers in the pool supply area - it is normally used to adjust the pH in swimming pools. After the copper turns green you can neutralize the acid by soaking or sponging the trellis with a solution of baking soda in water (A one pound box of baking soda in a gallon of water.)
• A less dangerous but much slower acting chemical is vinegar. You will only get noticeable results if you can put your trellis (or trellis parts) in a tub of vinegar and let it soak for several days. You can buy gallon jugs of white vinegar (normally used for pickling) pretty cheaply.

Can I sell what I make? What should I charge?

Yes, you can do anything you like with the trellises you make, whether they are made from designs in the Trellis Craft book or not.

I can't really answer the question about what to charge. That will vary by (among many other things) the amount of copper in the trellis, the price of copper at the time you make the trellis, how much time it takes you to make the trellis, how you advertise what you make, and whether there are enough people in your area interested in what you make.

To get a ballpark idea of what to charge, visit your local home centers and nurseries and see what they charge for different size (probably steel or wood) trellises. You can also do an Internet search on "copper trellis" and see what some Internet and mail order companies charge.

One tip: you may be able to sell more trellises if you offer a complete set of pot, plant, and trellis. Or if you sell at places like craft fairs, you could at least set up some displays complete with pots and plants so people can see your trellises "in action".

Many vines that grow well on trellises in pots are easy to start from seeds or cuttings, so the plants would not be a large cost.

My pipe kinks when I bend it. How do I prevent that?

• Thinner walled pipe kinks more easily than thicker walled pipe. That means you should use "type L" pipe instead of "type M" pipe for bending. See page 6 of the book.
• Slow and steady is what to aim for when bending copper pipe with a conduit bender. Pipe that kinks when you bend it quickly, or kinks when you start a bend, stop, and start again, may bend just fine if you bend with one smooth steady motion.
• Be sure you are not bending past 90° with a conduit bender. Trying to bend more than a right angle will certainly kink or flatten the pipe.
• If all else fails, you can fill the pipe you want to bend with a fine grained dry sand as an internal bending support. The home centers have a type of sand usually called "play sand" that is mostly fine grained sand with no bits of gravel.
  1. Tape closed one end of the pipe you want to bend, with duct tape or shipping tape.
  2. Fill the pipe with sand. Tap the pipe on a hard surface to settle the sand, and fill it again if necessary. Tape the other end of the pipe closed.
  3. Bend the pipe as usual, then pour out the sand.

   

• This is another method, from Yard Lady in North Attleborough, MA:
• For 90 degree bends ... I used bending springs inside the pipe to keep it from kinking. I cut off the flare at the end of the spring, affixed a string, and oiled it. It slipped out quite easily each time and the bends are very smooth.
• I tried the tube bending spring on the outside. That did not work. I had to use a smaller size and insert it into the pipe after I cut off the flange. Warn people to stay clear of the spring exiting as it can shoot out real quickly when you tug on the attached string. But it allowed two 90 degree bends back to back for 180 degrees to come out baby-bottom smooth.
• (Author's Note: bending springs are available in the plumbing section of the home centers. They are normally used on the OUTSIDE of soft copper tubing. Yard Lady is describing how to use them on the INSIDE of hard copper pipe.)