Potted plants last longer than arrangements of cut flowers and make equally attractive centerpieces. These potted plants, placed in terra-cotta containers embellished with decorative sands, make wonderful shower or wedding favors that will be enjoyed long after the party is over. To make, simply brush white latex paint on the exterior, rim, and interior top of each pot. While the paint is wet, roll the pot in a large, shallow container filled with sand. (Martha uses regular construction sand mixed with a few handfuls of colored art sand.) While most potted plants make beautiful centerpieces, a few that work especially well are: Miss Muffet caladiums, tuberous tropical plants that thrive in warm, sunny gardens; false heather (Cuphea hyssopifolia), which make good houseplants; maidenhair ferns (Adiantum pedatum); begonias; and flowering myrtle (Myrtus communis), which can also be trained as a topiary. For a truly extravagant arrangement, cluster three potted orchids in the center of a table.