Native to Australia, the bottle brush (Callistemon citrinus) is an ornamental flowering shrub that reaches up to 12 feet high and 15 feet wide. The red flowers on this plant bloom from July to August and resemble bristle brushes used to clean drinking glasses and bottles, hence the name. This plant thrives in USDA zones 9 to 11. It is spread by suckers, so early spring or late winter trimming is essential to prevent it from spreading and forming a thicket. Trimming inferior branches also helps maintain its shape so it looks beautiful when swaying to a light breeze.
Snip off low-lying branches on the bottle brush first to make way for people, vehicles or lawn equipment to comfortably pass beneath the canopy. Use handheld shears and snip off branches on the trunk that touch the ground until 4 to 5 feet from the base. The bottle brush plant will already look less congested.
Clip off damaged, dry or diseased branches on the plant. Also remove branches located toward the inside of the bottle brush that cross other branches, thus allowing more sunlight and air to pass through the foliage. Do not trim aggressively; only remove the current season's wood to achieve the desired shape and size.
Cut visible suckers growing from the base of the trunk. Suckers extract nutrients from the plant.
Shape the canopy of the bottle brush plant so it resembles an umbrella, trimming branches off so they spill in an outward direction from the trunk. Keep stepping back to review your work so you conform to the natural shape without altering it, and do not get aggressive in your trimming efforts.
Collect the clippings in a tarp or wheelbarrow and dispose appropriately.