From: "Craig Allen" callen at fairchildgarden.org> on 2003.01.08 at 18:13:00(9773)
The following note is what I send out to people that ask about the construction of Fairchild Garden's epiphyte display. I have purchased my cork bundles from: OFE International, Inc., 305-253-7080; 12100 S.W. 129th Court, Miami, Florida 33186-6421
Epiphyte tree construction
A pipe frame is assembled from 4, 6, and 8 inch PVC irrigation pipe and fittings then covered by a skin of cork bark.
At the base of the tree is a concrete anchor with an embedded lag bolt. The tree base is bolted to this foundation and all the 1/4" stainless cable is clamped around the heavy bolt and threaded through the pipe and tied to the overhead beams. The stainless steel cable is actually the support structure, as the PVC is not strong enough to support itself.
The PVC pipe frame isn't glued but is screwed together using galvanized screws. I do it this way so that I can rotate the fittings or change the whole structure if the shape turns out to be unconvincing as a tree.
The cork bark covering is screwed on with galvanized deck screws, reinforced with steel washers under the screw heads. 'Liquid Nails' construction adhesive is spotted around the pipe to strengthen the corks bond to the frame. The washers spread the pressure on the cork to a wider area so that the screw will not go all the way through the soft cork. If the screws are noticeably visible after construction and planting, a dab of liquid nails and a cork chip covers the exposed metal, or even brown marker.
In my original structure, great attention was put to lining up furrows in the cork to help the believability of the branches, but that proved to be a waste of time after the plants were added.
After the large cork sections are attached, cut cork pieces are used to fill gaps between large slabs. Small gaps can be filled with cork chips, Osmumda fern fiber, or bits of moss. If a constructed tree is going to be heavily planted many of these small gaps shouldn't be visible any way.
The living epiphytic plants were attached using thin aluminum wire as a strap with small deck screws. Wire that is twisted around a screw then snuggly crosses the stem or rhizome and twists around the second screw. As you tightened the screws the wire tightens on the plant, holding most plants. Small plants can be attached with large ungalvanized electrical staples or even glued with the 'Liquid Nails'.
Most epiphytes readily attach to cork. I have had problems with cattleya orchids. I am not sure if the problem is an aversion to the cork, or staying too wet. Most show no root attachment to the cork bark.
...As far as how to make it look real... I just did it by intuition, but if you could see under the skin, there is just as much structure made from fittings as pipe. They make a number of fitting with 22% and 45% bends. Used lots of them to make your branches twist. Avoid long straight sections, even though it would lower costs. The fitting (example 8" connector with a 6" side tube at 22% angle) is the most expensive but the most important for looks. 8" for large trunks, down to 4" for smaller branches. Do not cantilever any branches over peoples heads more than 3' with out support. The PVC is not that strong, a heavy epiphyte load is heavy indeed.
I can't think of anything else except that after plants are attached all the areas that bother you tend to disappear. If you do a fallen branch as I did, try to keep most of the branches aiming in the same general direction as if it was from one side of the tree. I rearranged my first display when I was 1/2 way through because it wasn't looking natural.
Craig M. Allen
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