Bottlebrush (Callistemon) Ultimate Growing Guide

What is a Bottlebrush? 

The genus Callistemon or bottlebrush encompasses a range of blooming shrubs and smaller trees. Belonging to the Myrtaceae family, bottlebrushes are closely related to other Aussie favourites like melaleuca plants, eucalyptus plants and the lilly pilly. 

Discovered by the renowned botanist Sir Joseph Banks, the Callistemon genus includes over 40 different species and many hybridised sub-cultivars. 

This ornamental landscaping plant produces green, sometimes green-grey foliage and large, cylindrical flower spikes, which bloom with radiance throughout the summer season.

Depending on the variety, cultivars bloom in bright red, crimson, yellow, pink, cream and white. 

How to Grow Bottlebrush

Callistemon plants are known to be fairly easy to establish and even easier to maintain. As these are known to be hardy plants, they generally tend to thrive even in not so optimal conditions. 

The most important growth and Callistemon care factors include the climate, sun, water and soil. 

Ideal Conditions for Planting Bottlebrush

Growing Climate

The bottlebrush will grow quite happily in most climates, especially those in Australia. Depending on which variety you’re growing, extreme cold conditions are not always suitable. Ideally, you’ll want to grow your bottlebrush in a temperate climate that receives regular summer rains.

The best-known regions for bottlebrush growth include the tropical north or temperate south of Australia. It can tolerate wet conditions, but it is also somewhat drought tolerant, making it a versatile addition to flower gardens as well as a good choice for xeriscaping.

Planting Location

It’s not new news that flowering plants need a decent level of sunshine to bloom. Bottlebrush plants can grow in both full-sun and semi-shaded conditions. However, the more sun it receives, the more likely it is to bloom vigorously. 

Water Bottlebrush

Younger and establishing plants will require regular moisture and water. As such, younger plants should be watered almost weekly, in the absence of rain. Once established, however, it becomes incredibly drought-tolerant and can take a few weeks without needing water.

Mulching at the base of the stem is a great way to help the soil retain moisture during particularly hot and dry spells. 

Best Soil to Use

When it comes to soil, the bottlebrush is not particularly picky. However, ideally, you’ll want to have a rich, peat soil mixture. For soils that are particularly poor, it is recommended to improve soil with some compost before planting.

It is also incredibly tolerant of salty soils, so it can grow fairly easily in coastal regions. Besides these features, your Callistemon should grow fairly happily and won’t require much more of your attention.

Depending on where you are growing your bottlebrush, in a pot or as part of a hedge, annual pruning can be done to control shape. Here is our review on the best garden secateurs for the job. 

Propagating Bottlebrush Plants

Bottlebrush plants can be propagated by means of seeds and cuttings. Semi-hardwood cuttings can be taken in mid to late summer. Cuttings should be 4 to 8 centimetres in length and include a few leaves at the end of the cuttings. The common planting method for cuttings can be followed. 

After flowering, bottlebrush plants also produce a wealth of seed pods. These pods can be taken and stored until the seeds are released. Be sure to keep your seed pods in a warm, dry place for a few weeks.

Once released, seeds can be sewn into a rich seeding mix during the spring and summer. 

Planting Bottlebrush

When planting your bottlebrush into your garden, be sure to pick a semi-sheltered area that receives plenty of sunlight. Dig a hole that is twice the size of the root ball, tousle the roots lose, place into the hole and backfill.

It is recommended to create a smaller ring around the base of the stem, which will help the soil retain moisture. It is possible to grow your bottlebrush in a pot, especially the smaller and dwarf varieties. 

When growing in a pot, it’s essential to pick the right spot and provide your plant with a rich yet well-draining potting mix. Tousle the roots lose before planting and pressing the soil down to remove air pockets. 

Mulching with sugar cane or wood chips is also advised when growing in a pot.  

Potential Bottlebrush Pest & Disease Problems

Bottlebrush plants are not often plagued or troubled by pests or infections. Sometimes, when conditions are sub-optimal for a longer period of time, it is possible for your bottlebrush to develop mould or be plagued by scale insects.

These can be easily treated with a horticultural spray. 

The other issue, which has been raised by gardeners, is the threat of the Callistemon Sawfly Larvae, which invade and feed on the leaves of the bottlebrush. 

For smaller invasions, it can generally be treated by a rigorous prune of all the affected foliage. For larger infestations, a caterpillar killer can be used to treat your plant. 

Bottlebrush Frequently Asked Questions

Is the Bottlebrush an Australia Native? 

The Callistemon is one of the most popular Aussie natives. In fact, it’s one of the hardiest endemic species that you can grow. 

Is the Bottlebrush plant Poisonous?

Unfortunately, the leaves and seeds of the bottlebrush can be poisonous when ingested. As such, it’s absolutely essential not to ingest any parts of this plant and to use gloves when working with areas that may release sap.

In some instances, the ingestion of bottlebrushes can be fatal both for humans and livestock. 

Can You Grow Bottlebrush as a Hedge?

Many of the lower growing cultivars, like the crimson and glaucus, are great options for flowering hedges. They are somewhat slower growing in comparison to other cultivars, and have dense foliage which provides a screening effect. 

Be sure to have the best hedge trimmer handy by reading our review and buying guide. 

Do Bottle Brush Trees have Invasive Roots?

The roots are slower-growing and are not considered to be invasive. As such, you can safely grow your bottlebrush along flower beds, walkways or walls. 

Why is My Bottlebrush Dropping Leaves?

Browned, dried out and crumbled leaves are a sign that your bottlebrush could be in distress. This is usually caused by an extreme lack of water. Take care to monitor the level of soil moisture.