Sweet broom (Genista spachiana), also called Easter broom, becomes a somewhat rounded shrub with pointy, arching branches 6 to 10 feet tall and equally wide. Fragrant yellow flowers cover the plant in early to mid-spring. It's best grown in U.S. Department of Agriculture hardiness zones 9 through 11.
You can prune dead branches away any time of year on the sweet broom. Any other pruning tasks are best scheduled immediately after the flowering ends, between mid- and late spring.
Pruning results in lush regrowth across the summer. Use two types of pruning techniques on this shrub. Heading back, or deadheading, is trimming back branch tips after flowering to shape the plant. Some people shear the plant in this manner into a uniform geometric shape. Hard prune the oldest branches that didn't flower well or are overly large and woody to 5 inches tall.
Heading back causes the plant to become denser and fuller with more abundant flowers the following spring. Removal of oldest branches helps control plant size.