I will find it hard to get used to saying Melaleuca as the new name for some of my favourite Australian plants such as ‘Captain Cook’, ‘Endeavour’ and ‘King’s Park Special’. But this is what it might come to if the botanical and horticultural world accepts a concerted push in the world of Australian botany to merge the genus Callistemon with its close relative Melaleuca.
The argument is that the differences between the two groups are insufficient for them to be kept separate. The rationale is explained in this excellent article on the website of the Australian Native Plants Society (Australia).
To put it in simple terms, both groups have flower heads that look like old-fashioned bottlebrushes. In fact, the common name for callistemon is bottlebrush, while melaleuca are known as honey myrtles or paperbarks. The two groups have common the fact that the flower heads consist of groups of individual flowers that feature colourful stamens. Generations of horticulturists and gardeners have learnt that the difference between the two groups is that the stamens in melaleucas are in little bundles while they are free in callistemons. Sounds simple, but apparently some species do not fit neatly into this differentiation, such as the weeping bottlebrush (Callistemon viminalis) where the stamens are all united together at the base.
I know that the gardening public loathes name changes like this but there is a potential silver lining in the bottlebrush imbroglio! Another factor in the reclassification is the burgeoning knowledge of genetic information through DNA analysis which apparently is showing that the two groups are much more closely related than previously thought. As a plant breeder I am particularly excited by this new knowledge as it might mean that I can hybridise the various melaleucas and callistemons to create beautiful new cultivars. Let’s contemplate some of the possibilities that these two genera bring to the gardening table.
In the wild, both groups usually inhabit areas that are periodically wet i.e. they often live along water courses that flood from time to time. This means that they adapt well to a wide range of soil types, from clays to very sandy soils, making them an outstanding choice for difficult soil types in the garden, and also rain gardens where they tolerate temporary inundation followed by dry periods. When it comes to flowering, Callistemons mostly have red flowers (although there are exceptions amongst its many cultivars), and they are renowned for spectacular mass displays in spring, particularly in red.
Melaleuca, on the other hand, comes in a wide array of colours, such as pinks, purples, oranges and yellows and tend to have a longer flowering period without the spectacular crescendo of their Callistemon cousins. Combining the attributes of some of the more spectacular members of each group is an intriguing prospect.
Another feature of both groups can be very colourful new foliage growth with cultivars such as Callistemon ‘Great Balls of Fire’ and Melaleuca ‘Claret Tops’ having established themselves as some of the most useful Australian landscaping plants to appear in recent times.
Another interesting feature is the essential oils produced by these plants with Melaleuca alternifolia being widely cultivated for its medicinal oil (confusingly marketed as tea tree oil). Imagine having a hedge that combines colourful foliage, flowers and can also be harvested to give an oil to relieve colds and flus!
Melaleucas and callistemons have flowers that also produce copious amounts of nectar that also make them great attractors of bird life. Use them to create informal screens and formal hedges that will bring honey eaters and spinebills into an Australian garden. Or if you garden in the Americas you may be rewarded by visits from your local hummingbird population.