Topiary is the art and practice of cutting trees, shrubs, and bushes, into ornamental forms. It derives from a Latin word for a landscape gardener, and by extension, to the word for "places" (as manifested in our present day word "topography".)

It dates back at least to Roman times, and many Roman villas had impressively created pieces of topiary in their gardens. The practice also flourished in Eastern cultures, where it is related to, but not the same as, Bonsai (the latter tends to preserve the form of the natural tree, rather than metamorphosing it, but does so in miniature).

In Europe, the art flourished in the 16th century when, interestingly, there is also evidence of women practising it, with a preference, sometimes derided by their male counterparts, for peacocks. But veritable menageries seem to have been formed from hedges, trees, and bushes, with some full-flung hunting scenes, although some purists preferred geometric shapes.

In the 18th century, the satirist Alexander Pope more or less slew the fashion for topiary with one sarcastic essay, but it saw a renaissance in the 19th century, and remains popular today, although it is also possible to "cheat", often employing the same materials as artificial Christmas trees!

More Info: en.wikipedia.org