Callistemons are closely related to Melaleucas, which also have ‘bottlebrush’ shaped flower spikes. Botanists, especially those at the Australian National Botanic Gardens in Canberra are currently closely studying these plants to determine how they are best classified. It appears that Callistemons could be renamed as Melaleucas sometime soon.
Callistemon subulatus grows along the banks of watercourses of coastal and tableland districts, south from Sydney to Victoria. In its natural habitat, they grow from one to sometimes 3 metres high.
I planted some of these plants about 12 years ago in my garden, in the northern Sydney suburb of Westleigh and they have all grown to about 1.2 metres high. They are still growing well, even though the soil is now much drier and they only receive dappled morning light and some full late afternoon sun. Very different from the full sun and moist soils that I enjoyed when I first planted them.
They receive no supplementary watering and after good soaking rains, especially in summer, I am rewarded with many red flowers which are 4–8 cm long and 40–45 mm diameter. The linear leaves are subulate or terete, mostly 2–4 cm long, 2–3 mm wide.
They are hardy plants worth growing if you require a small growing, colourful ‘bottle brush’.
Fertilising: A low-phosphorous fertiliser should be applied in spring and autumn and light vegetative mulch will help retain soil moisture and reduce weed growth.
Pruning: Tip pruning can be undertaken almost anytime that the flowers are not developing and this helps the plant to produce new shoots. The best type of pruning is to cut off 2/3s of the new flowers as soon as the flower is spent. This forces many new shoots that will produce next seasons flowers.
If your plant is old and needs a serious pruning, then cut it off near the base (with a slanting cut), water well and give it some fertilizer and you will be rewarded with masses of new growth. Not for the faint hearted, but it works.
Callistemon: from the Greek calli meaning beautiful and stemon meaning stamen.