GardenBanter.co.uk - View Single Post

17-04-2004, 07:42 PM

writes:
Am looking to grow grapes and was considering constructing a trellis out
of
1 1/4" galvanized pipe. I was planning on driving the vertical runs about
3
feet below grade(frost line here) and running 1 1/4" horizontal piping
runs
about 7 feet high off them. A few concerns came to mind.....the horizontal
runs will be about 10 feet long....is that long enough? The vines will be
trained along the piping. Due to the size of the piping will it tend to
get
too hot for the vines as the direct sun shines on them, thus burning the
vines and leaves? I'm in the northeast. Thanks in advance.

If you are concerned about heat, you might consider putting a sleeve of
PVC pipe around the galvanized pipe which would solve the possible heat
problem. When the vines are mature, the leaves should prevent potentially
damaging excess heat when, eventually, the PVC, not being designed for
out-of-the-ground exposure to sun and elements, will degrade. It can then
be removed if you want as it will be quite "cuttable" by that time. If
you decide to do that, you will, of course, put the PVC pipe on the
lengths before you fasten the joints. It might look a bit peculiar at the
joints with the gap in the PVC, but that will fill with leaves and be
hidden. Of course, you could put a big artificial flower there to
disguise it until the vines are tall enough to conceal it (or a bunch of
artificial grapes!).g Seriously, you can probably think of a way to
disguise it if you want to do that.

A custom arbor trellis is in the future for my new kiwi plants but in the
meantime, they have a temporary trellis which can be removed when the
permanent one is built. I have aluminum electrical conduit supporting the
plants on the lower horizontals with PVC on the upper parts, and it seems
to not be a problem with heat on the aluminum which was a concern. It
does get quite hot on sunny summer days but, thus far, it hasn't caused
apparent damage. The switch to the PVC was also because of heat concern,
though the permanent trellis will be metal.

It seems logical that the leaves of your new plants will protect the plant
on the verticals as they vine up the pipe and the same would be true of
the horizontals, keeping in mind that there will be leaves to shade the
pipe during any time of year that it might get hot enough to potentially
damage the plants. Something else you might do to reduce the heat
transference is to fill the vertical pipes with sand or dirt once they are
in the ground to help reduce conduction though that would be entirely
experimental since it would still conduct along the pipe. If it were me
and concerned about the heat issue, I'd use the PVC sleeves. Green might
seem more appealing, but black blends in better and tends to disappear in
the mind's eye as well as not obviously fading. I have a black PVC
support for the bird feeder in the middle of the garden and it doesn't
attract the eye like green or white would.

BTW, you will want to be certain to imbed your pipe in a non-corrosive
material or by the time the vines are mature, the pipe will be
weakened/corroded. Definitely consider cutting it and adding a joint
about a foot above the soil level since the damage will be when your
grapes vines are mature and at their very best many years from now.
Depending on your soil, consider a good layer of gravel under it to pull
away the excess water (under, not around). I'd also put a PVC sleeve (at
least an inch larger than the metal) around the pipe and fill the space
betweent the pipes with a good sand to keep the soil contact away from the
metal pipe. That way the corrosive action of the concrete and soil is on
the PVC and not the pipe. Many years ago, I typed a very revealing report
by a pipe supplier sales person that described in detail the corrosive
nature of different soils on the many types of metal pipe. He had
definitely done his research and was asked to present it at many seminars
across the U.S. and received some prestigious industry awards for it. Some
last as little as 15-20 years! Having replaced water lines to older
houses, I have no doubt this is a major problem. I worked for a utilities
contractor, and he took some pretty rough-looking stuff out of the ground.
Remember what you see is not what is supporting the vines; the main
support is the part you cannot see since everything else rests on that.

Enjoy your grape adventure.

Glenna