Introduction
This popular evergreen tree has a dense, multi-trunked, low-branching, pendulous growth habit and a moderate growth rate. Mature specimens can reach 25- to 30-feet tall in 30 years, but most trees are seen 15- to 20-feet high and wide. The narrow, light green, 3- to 4-inch long leaves tend to grow only at the ends of the long, hanging branches, creating a weeping effect. The cylindrical, bright scarlet blooms, several inches long and 1.5-inches wide, are composed of multiple, long, bristlelike stamens. Flowers are larger than the species. These blooms appear in great abundance March through July, less so throughout the year. The flowers are followed by persistent woody capsules that are not noticed unless you are close to the tree.
General Information
Scientific name: Callistemon viminalis
Pronunciation: kal-liss-STEE-mawn vim-min-NAY-liss
Common name(s): 'Red Cascade' Weeping Bottlebrush
Family: Myrtaceae
USDA hardiness zones: 9B through 11 (Fig. 2)
Origin: not native to North America
Invasive potential: little invasive potential
Uses: hedge; deck or patio; specimen; screen; container or planter; street without sidewalk; parking lot island < 100 sq. ft.; parking lot island 100–200 sq. ft.; parking lot island > 200 sq. ft.; tree lawn 3-4 feet wide; tree lawn 4–6 feet wide; tree lawn > 6 ft. wide; highway median
Availability: somewhat available, may have to go out of the region to find the tree
Description
Height: 15 to 20 feet
Spread: 15 to 20 feet
Crown uniformity: irregular
Crown shape: weeping, round
Crown density: open
Growth rate: moderate
Texture: fine
Foliage
Leaf arrangement: alternate (Fig. 3)
Leaf type: simple
Leaf margin: entire
Leaf shape: lanceolate, linear
Leaf venation: parallel
Leaf type and persistence: evergreen
Leaf blade length: less than 2 inches, 2 to 4 inches
Leaf color: green
Fall color: no color change
Fall characteristic: not showy
Flower
Flower color: red
Flower characteristics: very showy
Fruit
Fruit shape: round
Fruit length: less than .5 inch
Fruit covering: dry or hard
Fruit color: brown
Fruit characteristics: does not attract wildlife; not showy; fruit/leaves not a litter problem
Trunk and Branches
Trunk/bark/branches: branches droop; not showy; typically multi-trunked; thorns
Pruning requirement: needed for strong structure
Breakage: resistant
Current year twig color: gray
Current year twig thickness: medium
Wood specific gravity: unknown
Culture
Light requirement: full sun
Soil tolerances: sand; loam; clay; acidic; slightly alkaline; well-drained
Drought tolerance: high
Aerosol salt tolerance: moderate
Other
Roots: not a problem
Winter interest: no
Outstanding tree: no
Ozone sensitivity: unknown
Verticillium wilt susceptibility: resistant
Pest resistance: resistant to pests/diseases
Use and Management
Weeping bottlebrushes should be grown in full sun, preferably on moist, well-drained soil. Although they can tolerate some drought, best flowering and growth is obtained with ample moisture and regular fertilization. Be sure the soil drains well, as roots often rot in wet soil. The brittle wood of weeping bottlebrush may make it unsuitable for windy areas, but this is usually not a problem in most locations. They are not suitable for street tree planting due to the weeping growth habit, but will make nice plantings along streets in wide medians. Lower branches can be removed so cars can fit beneath in parking lots, where the trees grow well in the restricted soil space. Occasional pruning of pendulous branches will be required for vehicle clearance. One of the best uses is for lawn specimens, or screens on large properties, with a regular maintenance program.
Callistemon citrinis and Callistemon rigidus are hardy in the southern part of USDA hardiness zone 8b.
Propagation is by cuttings.
Pests
Mites and witches broom can be troublesome.
Diseases
Root rot in wet soil, and canker. A twig gall, formed in response to a fungus (Sphaeropsis tumefacens), can disfigure the tree. The tree is often short-lived due to disease.
