Bottlebrush are evergreen, woody native shrubs or small trees that are ideal for the garden, as their beautiful bottlebrush blooms attract nectar-eating birds and insects.
What you need to know about bottlebrush
Name: bottlebrush (Callistemon).
Height: 60cm to 5m tall.
Foliage: evergreen.
Climate: Australia’s tropical north to the temperate south. They often grow in damp or wet conditions, such as along creek beds or in areas prone to flooding. Most species are frost-tolerant.
Soil: all soils except highly alkaline.
Position: full sun or full sun/part shade.
Flowering: mostly spring and summer, spot flowering at other times.
Feeding: yearly feeding with a native, low-phosphorus fertiliser.
Watering: drought-tolerant once established. Weekly to twice weekly watering in summer and weekly watering in winter.
Appearance and characteristics of a bottlebrush tree
There are more than 30 species of bottlebrush, and many hybrids and cultivars including small plants just 60cm tall, with many popular bottlebrush 4m or less in height.
Callistemon species are called bottlebrushes because of their cylindrical, brush-like flowers that resemble a traditional bottle brush. Many have bright red brushes, but there are also forms with cream, yellow and pink blooms. Most flower in late winter and spring, the brush being made up of a number of individual flowers.
The new leaves of many bottlebrushes are very ornamental. These leaves are often coloured and, in some species, they are covered with fine, soft hairs.
Bottlebrush species
Albany bottlebrush (Callistemon glaucus): 2m tall and wide, scarlet brushes.
Lesser bottle brush (Callistemon phoeniceus): 2–4m tall and 2–3m wide with scarlet brushes.
Weeping bottlebrush (Callistemon viminalis): fast-growing weeping bottlebrush tree that grows to 5m, with rough scaly bark and red flowers.
Crimson bottlebrush (Callistemon citrinus): bright red flower spikes. Suits wet conditions and usually reaches 4m tall.
Kingaroy bottlebrush (Callistemon formosus): a shrub for tropical and frost-free areas with lemon-coloured flower spikes throughout the year. Plants grow to 3m with weeping branches.
Alpine bottlebrush (Callistemon pityoides): A compact bush that grows to about 1–2m tall and needs moist soils. Frost-hardy with yellow flowers.
Bottlebrush hybrids and cultivars
Many cultivars have been selected from natural variants and hybrids between species.
“Green John” and “Little John”: dwarf form of Callistemon viminalis; grows to 60cm tall and 1m wide. Green John has green foliage and Little John blue-green foliage. Both with red brushes.
“Macarthur”: dwarf form of Callistemon viminalis; grows to 1.8m tall and 1.5m wide with red brushes.
“Slim”: a narrow form of Callistemon viminalis with red flowers and a growth habit 1.3m wide and 3m tall, making it good for screening.
“Scarlet Flame”: a fine-leaf variety with red new leaf growth in autumn and spring. Grows to 1.5m tall and 1m wide.
Callistemon “Harkness”, Callistemon “Hannah Ray” and Callistemon “Dawson River Weeper” are big shrubs growing 4–5m tall. All have an attractive weeping habit.
“Captain Cook”: one of the best smaller-growing forms, 1.5–2m tall and 1–1.5m wide.
“Endeavour”: a selected form of Callistemon citrinus that is an upright and compact shrub with big flowers in spring and autumn, growing 2–3m tall and wide.
“Kings Park Special”: slightly weeping variety, and one of the best flowering forms, 3–4m tall and wide.
“Great Balls of Fire”: a form of Callistemon salignus which is a good hedging plant. It has red new growth and dense foliage to 1.8m tall and wide, but no flowers, and can be kept lower with regular pruning when young.
Callistemon “Reeve's Pink” and Callistemon “Mauve Mist”: produce attractive pink flowers; grow well near a wall in cold areas and flourish in warmer climates.
Uses for bottlebrush
Dwarf species like “Green John”, “Little John” and “Great Balls of Fire” make excellent hedges, and narrow varieties like “Slim” are good for screening. Many of the bigger varieties make fantastic evergreen, feature trees. All varieties provide good habitat for native birds and animals.
How to plant and grow bottlebrush
Bottlebrush needs regular summer water. It naturally grows along creek beds and in areas prone to flooding, so appreciates regular watering. However, most will tolerate drought and limited maintenance.
Plants grown in full sun produce the best flowers.
Bottlebrush grow well in a wide variety of soils, except those that are highly alkaline. Feed yearly with a complete native fertiliser and mulch around the drip line to conserve moisture.
How and when to prune bottlebrush
Pruning stimulates branching, resulting in more flowers in subsequent years. Plants should be pruned after flowering, just behind the spent flowers. If this is not done the flowers produce small woody fruits containing the seed, which form in cluster along the stem.
For best results, follow these tips when pruning:
- Keep pruning to a minimum by clipping a couple of inches below the tip.
- Prune as needed when pruning for shape.
- Straggly bottlebrush can be severely pruned.
Diseases and pests affecting a bottlebrush tree
Bottlebrush are not really troubled by many pests or diseases, provided they are growing in conditions which suit that variety.
Sometimes sooty mould develops, and this is usually due to the presence of scale pests. Several sprays of horticultural oil will kill the pests, and the sooty mould can be hosed off with a strong jet of water.
The Callistemon sawfly larvae can also attack and skeletonise leaves. For small outbreaks, prune off any damaged parts and infestations. For larger outbreaks, treat with a caterpillar killer like Dipel or Success.
If you like this then try
Grevillea: available in a variety of forms with flowers from fire engine reds to oranges and whites.
Kangaroo paw: has a flower form that’s unique in the botanical world, and comes in colours to suit every need.
Eucalyptus tree: known for growing into some of the tallest trees in the world, there are plenty of small and showy varieties that are great for smaller gardens too.
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