In theatre the final method of construction of a piece depends on a variety of details. One issue is how labor is paid for. Is it salary, and thus doing something labor intensive is okay? Is it hourly, but out of a budget that doesn't impact show budgets or does the amount of labor used directly effect the budget of a production. In some theatre settings, and in the commercial shop I work in, it is often cheaper to buy something than it is to fabricate it. Thus for a recent project we looked at using flexible bark. The pieces were pricey at about $600 a sheet, but for us to manufacture something similar in house would cost more. Between labor and materials - for us to match the 600 price we would have to be able to mold / carve / paint / and do any sampling for the piece in about 3 hours. There is of course a exception. In the case above we would use less than a sheet. If we were to cover a stage full of trees, economy of scale would probably reverse this. In this case, I would look at it from both directions - the cost of buying premade pieces versus fabricating in house. Once the size is large enough, it makes more sense for us to fabricate. A good example of this is a urethane brick that we have made for some museum exhibits. It's very realistic, and very durable - much more so than vacuform or the wood paneling, and we can easily make it wrap corners. But it was economical because the prototyping, testing, and development was dispersed due to the amount of coverage. All in all, price wise we were right in line with other suppliers, but achieved a better quality of product.
Earth Flora also has a realistic bark for sale, but not as many options and a much smaller size. The question becomes with using these is how you handle seams.