Excerpt
Bromeliads can be grown on almost any surface and in almost any medium, provided there is air circulation and water can drain away from their roots. However, chemically treated timber and galvanised or copper-treated metal should be avoided, since these leach out their chemicals. Pots obviously make suitable growing places, and scoria makes a good root-anchoring medium, though bark, peat, charcoal and perlite are often used. Stumps and logs can also provide sites for bromeliads. The rougher the surface, the easier it is for the bromeliad to gain a footing. Start them off by tying them on with natural fibre twine or something soft. Driftwood can be positioned imaginatively, the holes and crevices being used for anchorage. Bromeliads can also be attached to trees. Tying is not the only means of attaching bromeliads. Glues such as paper adhesive or PVA are often used, and for the delicate, spidery tillandsias that like dry places and are best indoors, a couple of dressmakers' pins are all you need.
Like palms, bromeliads are best in groups; solitary specimens are less successful in the landscape. If there isn't a suitable tree, try making your own. Any branches or timber will do, but a tall tree fern log is by far the most successful — the dark fibrous surface shows their colours to best advantage. To maintain a natural appearance, make use of materials like sphagnum moss or coconut fibre to retain moisture around the plant while it is becoming established. Perhaps the easiest, and certainly one of the most dramatic, ways of displaying bromeliads in the garden is to let the plants grow on a mound of rocks.