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
- 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.
do I keep my trellises bright and shiny?
- 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?
- Second, clean the completed trellis with steel wool as explained on
- 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.
- 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.
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
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
- 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
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
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
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
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.
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.
- Tape closed one end of the pipe you want to bend, with duct tape
or shipping tape.
- 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.
- 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