Callistemon (bottlebrush) is a genus of perennial shrubs with around 50 recognized species. Native to Australia, this plant commonly grows in many regions of the world, both wild and cultivated.
History
There is some confusion as to whether Callistemon is a genus in its own right, or whether these perennials should be classified as Melaleuca. Until 1998, there had been a distinction between Melaleuca and the Callistemon.
DNA research was carried out in the late 1990s and early 2000s with the result that almost all the species of Callistemon were transferred to Melaleuca. The only Callistemon that remains in the former group is accepted hybrids.
However, the discussion is still ongoing, with some botanists arguing that the DNA evidence used to reclassify was premature. Many commercial nurseries continue to refer to these plants as Callistemon.
Plant Facts
| Scientific name | Melaleuca citrina, Callistemon citrinus |
| Common names | Common red bottlebrush, crimson bottlebrush |
| Genus | Melaleuca |
| Family | Myrtaceae |
| Height | 3 to 15 feet (4.57 meters) |
| Width | 3 to 10 feet (3.05 m) |
| USDA Plant Hardiness Zone | Zones 8 to 11 |
| Native to | Australia |
| Blooming season | Summer |
| Flower colors | Red |
| Plant specific features | Cylindrical and unusual shaped red flower spikes |
How to Plant and Grow a Bottlebrush
These shrubs are widely available and should be planted after the risk of the last frost has passed. The planting hole should be just a little larger than the root ball and shallower in depth.
This will prevent the plant from sinking too deep into the soil. The hole should be backfilled with a mixture of potting compost and garden soil.
Where to Plant
The best planting site will be one in full sun. The bottlebrush shrub needs to be protected from cold winds. They do well when planted alongside other herbaceous perennials with similar growing requirements.
When to Plant
Container-bought bottlebrush plants should be planted in the spring, once the danger of frost has passed. However, if you are planting in a native or preferred growing area, you can plant a bottle brush at any time of the year.
Bottlebrush Care and Maintenance
Soil
The soil needs to be well-draining. Bottlebriush does not like to sit in wet or overly moist soil. They will thrive in most soil types, other than one that is excessively alkaline.
If necessary, you can add a soil conditioner such as organic compost or sphagnum moss to reduce the alkalinity. This will give an added benefit of improving the soil texture. You can repeat this every year.
Water
Until the bottle brush has grown a robust and strong root system, you need to make sure it doesn’t dry out at the roots. In its natural habitat, by streams and in damp locations, it grows a deep root system.
Once your plant is established, it is a drought-tolerant plant. Only rarely will it need extra water.
There is one exception which is the weeping bottle brush. This needs considerable and regular watering at the root level.
Fertilizer
To improve the flowering performance, apply a low-phosphorous (the “P” in N,P,K fertilizer compositions) fertilizer once or twice a year. A slow-release fertilizer will provide the plant with nutrients throughout the season.
It is important though that you do not over-fertilize this plant, nor use a fertilizer that is high in nitrogen. This will result in causing foliage to grow at the expense of flower production.
Sunlight
The sunnier the position, the better the bottle brush will flower. More than this, the shrub needs plenty of sunshine to grow and thrive.
Remember that if neighboring plants are too close to the bottlebrush, they can shade the bottlebrush, even if it is in a sunny location.
A lack of sunshine is the most common reason for a bottle brush not to flower or flower well. The sun needs to reach the foliage for at least six hours a day.
Pruning and Repotting
You can keep the bottle brush shrub in check, by pruning it. This will also keep it in a pleasing shape. However, if you prune at the wrong time of the year, you will lose flowers.
Make sure you do not prune when the plant has flower buds. The best time to prune a bottle brush is just after it has flowered.
Although it is feasible that the bottle brush will bloom all year long, the most prolific flowering period is in the spring and summer months. So it is after these flowers have finished that you should trim your plant.
Propagating
It is a fairly simple process to increase bottle brush plants. The two main methods from which to choose are sowing seeds or taking cuttings.
If you decide to sow the seeds from the bottle brush plant, then ensure that you are not taking seeds from a hybrid plant. Seeds sown from hybrids will not produce clones of the parent plant. If you have a hybrid, then propagate from cuttings, not from seed.
The seeds form at the tips of the long, spiky flower heads. After flowering, you will notice that there is a small, hard fruit. This contains hundreds of tiny bottle brush seeds.
If the seeds are not removed from the plant, they can remain for years before being naturally released.
Seeds should be stored after harvesting and kept warm and dry in a bag. After several weeks or months, the hard fruits will burst and release their seeds, which can be sown in potting compost in the spring.
If the bottle brush you want to propagate is maybe a hybrid, then you should take semi-ripe cuttings in the summer. Use a slightly woody stem about 6 inches (15.24 cm) long from the current season’s growth. Remove the lower leaves and any remaining flowers or buds.
The use of a hormone rooting powder will assist the rooting process. Then, cover the cutting with a plastic bag or the top of a clear plastic drink bottle. This will help to retain moisture.
It will be between two and three months before the roots develop, at which point you can remove the plastic cover. The following spring, plant the cuttings outside.
Pests and diseases
Most problems are easy to remedy and are mostly caused by soil or foliage that is too wet or humid. Wet soil leads to fungal diseases such as twig gall.
You need to cut off diseased branches which will have bloated and remove the plant debris. Then, dry out the soil and ensure that the drainage around the plant is improved.
If the wet soil is not treated and improved, a more serious fungal issue such as root rot can occur. This is untreatable and will kill the plant. It can also spread to neighboring plants.
The branches will die back, and the foliage and stems will turn yellow and droop. You can try to treat it with a fungicidal spray, but by the time you notice the symptoms of root rot, it is probably too late to cure the disease.
Another fungal disease that can affect the Callistemon is powdery mildew. This very common problem comes from watering above the plant and not around its base.
This leads to excess water resting on the foliage and the onset of the powdery mildew fungus. Fungicide spray is an effective treatment.
Verticillium wilt is less serious, but also a fungal disease. It is difficult to eradicate the spores that remain in the ground. You may wish to consider moving your plant to a new location.
Temperature and Humidity
Because this plant is native to Australia, it needs warm temperatures and a mild climate. If this isn’t possible, consider growing the plant as a pot plant where it can be taken inside during cooler months.
The bottle brush grows well as a container plant with a maintained temperature of around 15 degrees and careful watering. Even grown inside and with a warm temperature, the bottle brush still needs sunlight. If it doesn’t receive sufficient sun, it will not flower.
The bottle brush will tolerate some humidity; however too much can lead to fungal disease and rot.
Other Uses for Bottlebrush
There has been a review and research undertaken on the possible health benefits of the different parts of the bottle brush.
Treated as a medicinal herb, the plant C. citrinus has long been used for the treatment of rheumatism, and water retention and used as a mosquito repellant.
Dyes can be fabricated from both leaves and flowers of the shrub.
This species has a place in tea production too. The leaves and or the flowers can be used as an infusion. The infusion is made from the leaves, and the flowers are used as a sweetener.
It is unknown whether this plant is hazardous to people.
The wood of the shrub is extremely hard and can be used for both fuel and it burns well once seasoned and, if necessary, split.
As a plant, the weeping bottlebrush can be clipped and makes a very useful and attractive screen or hedge.
Types of Bottlebrush You Can Grow
There are around 50 species of bottlebrush documented, but common varieties include
Callistemon viminalis (weeping bottlebrush) is grown as a tree or, when trimmed to reduce its height, as a hedging plant. Left un-pruned, this species could grow to over 30 feet (9.14 m).
Usually, however, it reaches around 15 feet (4.57 meters) in both height and spread. It has graceful, arching branches and bears bright crimson flowers up to 5 inches (12.7 cm) long. Once it is mature, this tree develops gray-colored bark.
There are cultivars of this species which produce more showy flowers and are small growing. With their compact size, and attractive large flowers and foliage, varieties such as “Little John” are a popular garden choice.
This is beautiful and evergreen and is perfect for smaller planting space. Because it is slow-growing, it doesn’t really need much pruning.
Callistemon citrinis (lemon bottle brush), is so-called due to its leaves giving off a lemon scent when crushed. This is the common bottle brush, with crimson, red flowers and widely seen growing in gardens in the United States. The flowers are more showy than those of the weeping bottle brush shrub.
It should be noted that there is another, far less available, bottlebrush with the same common name. This is the Callistemon pallidus. This plant is also called lemon bottle brush, but because it has lemon-colored flower clusters, and not because of its scent.
Conclusion
Providing you have the climate (or can provide a warm place for the shrub in winter), a bottle brush is a tough and impressive addition to any garden landscape. Its nectar-rich flowers will attract birds and bees.
Once exclusively red-flowered, modern hybrids now produce blooms in shades of pink and mauve as well as the traditional crimson.
This can be a long-lived plant, given the right growing conditions, and provide a spectacular floral display every spring and summer, for decades.
*image by Yakov_Oskanov/depositphotos
