A topiary is simply an arrangement that takes the shape of a small, formed tree. Topiaries can be grown, of course, but they take upwards of half a year to form properly. It's much more common now to just create topiaries out of a few simple materials and once you get the idea, it's simple to make one on your own.
A very simple topiary is an old-fashioned sugarplum candy topiary tree. It simply involves using a small potted plant that resembles a tree and decorating it with pieces of candy that hang from ribbons. Little tulle bags can also be employed to hold the candies, as can little boxes in delicious colors. Or take a hint from a Victorian Christmas tree and create tiny paper “cones” that can be easily decorated, have a ribbon attached, and hung from the topiary tree. Intersperse them with multicolored bows and you're done. This would be a perfect centerpiece for the buffet table.
A created candy topiary tree involves using a pot, weights to balance the arrangement, a dowel or bamboo sticks, a low-temp glue gun or royal icing, a styrofoam form, and assorted candies,
Paint and decorate the pot you are using, if needed. Add some weights to the pot (pebbles are good) to balance the top-heavy arrangement. Tightly fit in a block of styrofoam for the dowel to stand in. Press the dowel into the foam deep enough so it will stand up unassisted. The dowel may be left as is, painted before sticking in, or wrapped with ribbons. Cover the styrofoam with sphagnum moss glued on with the low-temp glue.
If using wrapped candies, spray paint the styrofoam ball before sticking it onto the dowel. Use one of the colors of the candies to make the white less visible. Glue the candies onto the ball using a low temp glue gun, covering as much of the ball as you can. Tie a large bow under the sphere with a coordinating colored ribbon and you're done. Great candies to use with this are wrapped mints and Kisses.
If you are using unwrapped candies and want to be able to eat them, use the low-temp glue gun to attach aluminum foil to the sphere. Cover it completely. Now stick the sphere onto the dowel. Cover the whole ball with royal icing (you can purchase this from baking supply shops or at craft stores like Michael's. Stick in the candies and allow everything to dry. Use harder candies for this method like gumballs and lemon drops.
Candy topiary trees made with soft, unwrapped candies like candy
corn, shaped marshmallows, gumdrops, or gummy candies and simply
be stuck onto the form using halved toothpicks. Stick the cut end
into the foil-covered foam ball and attach the sweet onto the sharp
part of the pick.