Question: What do you recommend as a good plant to use as topiary in a container?
Answer: The classic choice is common boxwood (Buxus sempervirens), because it can easily be trained and trimmed into a wide range of shapes, and it is evergreen. Herbs also make ready subjects for topiary; sweet bay (Laurus nobilis) and rosemary are good choices. For a flowering standard (lollipop shape), try flowering maple (Abutilon spp.), tibouchina or tropical hibiscus, all of which respond well to pruning and staking.
To keep topiary in good shape, the advice is always to trim it "little and often." If this level of maintenance isn't for you, think about growing something that's naturally strong in its form. Good options are slow-growing succulents such as agaves and yuccas. Dwarf fan palm (Chamaerops humilis; Zones 8–10) is another interesting, architectural choice.