Fast-growing plants with colorful flowers carried in dense spikes or round clusters that consist mainly of long, bristlelike stamenshence the common name bottlebrush. Attractive to hummingbirds. Flowers are followed by woody capsules that can last for years and may resemble rows of beads pressed into bark.
Some bottlebrushes are naturally dense and compact (making good informal hedges); others are sparse and open (can be pruned up to become small trees). Those with pliant branches can be grown as informal espaliers. Very little routine pruning is neededjust remove any weak or dead branches after bloom or before spring growth. Don't cut into bare wood beyond leaves; if you do, plant may not send out new growth. Generally found in moist ground in their native Australia, bottlebrushes can withstand waterlogged soil. Normally tolerant of saline or alkaline soils but sometimes suffer from chlorosis (yellow leaves with green veins). Often severely damaged at 20F.
C. citrinus. LEMON BOTTLEBRUSH. Shrub or tree. Zones LS, CS, TS; USDA 8-11. Most commonly grown bottlebrush; most tolerant of heat, cold, and poor soils. Massive shrub to 1015 ft. tall and wide, but with staking and pruning in youth easily trained into narrowish, round-headed, 20- to 25-ft. tree. Nurseries offer it as a shrub, espalier, or tree. Narrow, 3-in.-long leaves are coppery when new, maturing to vivid green. Bruised leaves smell lemony. Bright red, 6-in.-long brushes appear in waves throughout the year.
Variable plant when grown from seed; look for cutting-grown selections with good flower size and color, such as 'Splendens'. Compared to the species, 'Violaceus' ('Jeffersii'), about 6 ft. tall and 4 ft. wide, has stiffer branches; narrower, shorter leaves; and reddish purple flowers fading to lavender. 'Mauve Mist' is the same but can reach 10 ft.
C. 'Perth Pink'. Shrub. Zones CS, TS; USDA 9-11. Dense, full growth to 610 ft. tall and wide, with weeping branches and deep pink flowers to 6 in. long in spring and early summer. New growth is pink.
C. rigidus. STIFF BOTTLEBRUSH. Rigid, sparse shrub or small tree to 20 ft. with 10-ft. spread. Zones LS, CS, TS; USDA 8-11. Sharp-pointed, gray-green (sometimes purplish) leaves to 6 in. long. Spring and summer red flower brushes are 212412 in. long. Produces prominent seed capsules. Least graceful of the bottlebrushes. 'Clemson Hardy' is a compact form (23 ft. tall and wide) with bright red flowers; it succeeds in Zones US, MS, LS, CS, TS and has withstood 8F. Bred in Georgia, 'Scarlet Torch' has a compact form, growing 9 ft. tall and 12 ft. wide.
C. salignus. WHITE BOTTLEBRUSH. Shrub or tree to 2025 ft. tall, 1015 ft. wide. Zones TS; USDA 10-11. Dense crown of foliage. Bright pink to copper new growth. Willowlike leaves 23 in. long. Pale yellow to cream- colored flowers appear in 112- to 3-in. clusters in spring, early summer. Train as small shade tree or plant 45 ft. apart as hedge.
C. sieberi. ALPINE BOTTLEBRUSH. Zones MS, LS, CS, TS; USDA 7-11. Shrub. To 36 ft. tall and wide, with a somewhat upright habit. Small (to 112-in.-long), dark green leaves densely cover the branches. Cream to yellow flowers in 112- to 6-in.-long brushes bloom from late spring to midsummer.
C. viminalis. WEEPING BOTTLEBRUSH. Shrub or small tree with pendulous branches. Zones CS, TS; USDA 9-11. Fast growing to 2030 ft. tall, with 15-ft. spread. Narrow, light green, 6-in.-long leaves. Bright red, 4- to 8-in.-long brushes from late spring into summer; scattered bloom rest of year. Not for windy, dry areas. As a tree, needs staking, thinning to prevent tangled, top-heavy growth. Leaves tend to grow toward ends of long, hanging branches.
'Little John' is a superior dwarf form to 3 ft. tall and wide, with dense growth and blood-red flowers in fall, winter, and spring. 'Captain Cook' is dense, rounded, to 6 ft. tall and wide; good for border, hedge, or screen. 'McCaskillii' has denser habit than others, is more vigorous (to 20ft. tall), and has better flower color and form.