Australian shrubs or trees known as bottlebrushes (Callistemon spp.) wield spikes of tiny flowers that bristle with long, colorful stamens, making them resemble bottlebrushes. The nectar-rich and usually red flowers are hummingbird magnets. The plants are simple to grow.
Choose a Bottlebrush
The hardiness of bottlebrushes varies, but they generally prefer U.S. Department of Agriculture plant hardiness zones 7 through 12. That said, most bottlebrush shrubs or trees won’t be reliably hardy in USDA zone 7. Two species that may survive in this hardiness zone and through USDA zone 10 are the yellow-flowered alpine bottlebrush (Callistemon sieberi), which blooms from late spring to the middle of summer, and the red-flowered
Lemon bottlebrush (Callistemon citrinus, USDA zones 8 through 10) boasts leaves with a citrus scent and 4- to 6-inch red flower spikes on and off throughout the year. The branches of weeping bottlebrush (Callistemon viminalis, USDA zones 9 through 11) dangle in a graceful, let-your-hair-down way, and its red flowers appear most heavily in late spring and summer.
Grow Bottlebrush Outdoors
For the most prolific flowers, ensure your bottlebrush site has the following:
Full sun, where it receives 6 hours or more of sunlight per day
Acidic, fast-draining, sandy loam with a pH between 5.5 and 6.5
10 to 15 feet between the bottlebrush and other trees or buildings
An established shrub or tree shouldn’t need supplemental watering except under drought conditions. To keep yours performing:
- Don’t let the flower spikes go to seed. Snip them off after they fade to encourage the bottlebrush to make more blooms.
- Feed it with an organic fertilizer such as 4-4-4. Apply 2 cups for each inch of the trunk’s diameter in early spring and again in early summer, scratching the supplement into the soil under the tree's canopy and watering the soil afterward.
Bring Bottlebrush Indoors
In colder zones, you can grow bottlebrush as a container plant by keeping it outdoors all summer and in a semidormant state indoors over winter.
Pot the plant in fast-draining, acidic potting soil such as a cacti-and-citrus mix. Place the pot in a sunny position, and water enough to keep the bottlebrush's soil moderately damp.
Fertilize the bottlebrush once every two weeks with an all-purpose plant food such as 24-8-16, using 1/2 teaspoon per gallon when the pot is indoors and 1 tablespoon per gallon when it is outdoors.
When nighttime temperatures outdoors drop below 45 degrees Fahrenheit
Move the bottlebrush to a warmer position in early spring, and begin feeding and watering it as usual again.
Adapt the plant gradually to more sun outdoors after the danger of frost has passed.