Small-sized trees well-suited for topiaries include Leyland cypress (Cupressocyparis leylandii) and bay (Laurus nobilis), as cited by Susan Berry and Steven Wooster in "Container Topiary."
Leyland cypress is a low-maintenance conifer that grows about 10 feet tall in containers. The tree has a rapid growth rate and dark green, needles. Plant in acidic, fertile soil for best growth. Bay is a broad-leaved evergreen with glossy, dark green, aromatic foliage used as a culinary spice. Grown as a topiary in containers, the tree grows up to 10 feet tall and blooms with small yellow flowers in spring.
Use Leyland cypress for taller, upright forms such as spirals and pyramids. Trim topiaries twice every year in spring and early or late summer. Propagate with semi-ripe cuttings taken in summer or spring. Bay trees are commonly used as standards or 6-foot tall topiaries. The tree has a fast growth rate and grows best in sunny spots.