Growing Callistemons in Large Pots

Bryon Williams

I started growing callistemons in some 25 years ago in the Melbourne suburb of Kew. It didn't take me long to realise that if callistemons were regularly pruned each year, fertilized and given a little tender loving care, they turned out quite different to the many Callistemon bushes I had seen in and around Melbourne with their twisted gnarled grey limbs and hundreds of old seed pods, some dating to the first year of flowering. I soon had a garden full of callistemons: beautiful bushy shrubs rewarding me with masses of bottlebrush flowers every year from mid October to late November.

I then encountered the dilemma every Australian plant enthusiast has to deal with sooner or later. I had no more space available on my standard sized suburban house block to plant my ever increasing collection of callistemons!

One hot summers day I was walking through Melbourne city centre when I came across a water tanker providing water for a number of semi advanced English trees growing in large concrete tubs situated along the city footpath. Why couldn't I do the same thing with some of my callistemons?

I have been growing callistemons in large plastic pots for a number of years with good results. My efforts have been rewarded with some excellent results: callistemons of all sizes will grow quite well in large pots. The main essentials are a reasonably large sized pot, good drainage, good soil and regular fertilizing and watering.

There are many forms of Callistemon citrinus ; the smaller growing cultivars are most suitable for containers. Select the thumbnail image or plant name for a higher resolution image (30k).

The unusual green-coloured flower spike of Callistemon pachyphyllus var.viridis . This form has a cascading habit of growth which would suit a large container. Select the thumbnail image or plant name for a higher resolution image (29k).

By growing callistemons in large pots, the shrubs are immune from the effects of unfavourable soil types, poor garden aspect and can be moved out to the ravages of the Victorian climate, be it century heat, wind, rain, hail, snow or frost. Furthermore, in the flowering season the pots can be grouped together to take advantage of the variations of colour of the brushes. Imagine three or four pots together with flowering Callistemon brushes in colours of white, red, pink and mauve!

I normally use large black plastic pots which are about 50 cm diameter and 40 cm in depth and can be purchased in nurseries for about $12 to $15 each. Remember good drainage is essential for growing any plants in pots.

My pots are filled with good rich natural garden loam from my stock of last year's leaf compost and lots of decaying leaf material. After I put my Callistemon in the pot, I mulch the surface soil with old Eucalyptus and Photinia leaves. All the plants are staked and tied with a soft but strong non-cutting tape and each pot is labelled with a permanent marking pen on coloured PVC sticky tape, with the name of the Callistemon, the date of planting and whether it is a cutting or seedling (if known).

The fertilizer used is blood and bone, applied on a wet soil surface and carefully watered in within the pot. This is applied a couple of times a year, once in autumn and again in late winter before the flowering time commences. (Don't use too much fertilizer at this time as the flower buds can turn to leaves!) An application of sulphate of potash in early spring will give you the colour that only southern grown callistemons can produce. There again, keep the mulch and organic matter up because sulphate of potash can leach the soil out a little.

"The fertilizer used is blood and bone, applied.....a couple of times a year, once in autumn and again in late winter....."

Callistemons in large pots can have problems with scale, particularly if they are sheltered (as a result of lack of air movement) and with this comes the problem of ants. Control of scale should keep the ants away. Sometimes in bad cases of scale, one is forced to use white oil, but for the most part, a fine spray of high pressure water from the hose will get rid of scale. Those of you who live near the coast subject to prevailing southern winds should have little trouble with scale.

Callistemons in large pots should be pruned just like those in the garden. Prune back behind the flower heads as soon as they fade, usually mid summer (early December in Melbourne), a little earlier on the coast. Depending on the age of the plants you can, if necessary, shape the bush at that time, too. The general flowering habits of callistemons is the same whether you grow them in containers or in the ground. Some flower regularly every year, year after year, whilst others for various reasons, miss a year or turn around and flower in autumn instead. These variations can be caused by pruning too hard or not enough, fertilizing at the wrong time, variations in water and the seasons. But, in general, if you treat your plants right, they will reward you with a floriferous display as only callistemons can.

Remember, some callistemons, but not all, grow in swampy and bog conditions. Make sure that these plants get plenty of water in the warmer months. They can also dry out quickly in winter, if the pots are kept under cover or in a sheltered position such as under the eaves of the house or against the wall sheltered from the prevailing weather. Therefore monitor regularly for the water needs of the bushes.

A word of caution, get yourself a little two wheeled trolley to move your pots, otherwise you risk doing the old back in; large pots can get quite heavy when filled with soil and even a medium sized plant.

Varieties of Callistemons for Large Pots

I've found that you can grow most of these types of plants in large pots, provided you are prepared to look after them with regular fertilizing, pruning and watering. Obviously the smaller varieties will be more suited for pot culture and are easier to handle. Some worth having a go in large pots would be C. 'White Anzac', C. 'Captain Cook', C. 'Little John', C. pityoides 'Cobberas Dwarf' and C. pearsonii.

Callistemons with white brushes are fairly uncommon. This is Callistemon citrinus "White Anzac". Select the thumbnail image or plant name for a higher resolution image (25k).

Those of you who want more of a challenge could try the large varieties such as C."Western Glory", C."Hinchinbrook Island" and even some of the old time Victorian veterans C."Mauve Mist", C."Burgundy" and C. "Reeves Pink".

I have had some success with some of the Queensland varieties in pots, viz C."Mr.Foster", C."Horse Paddock", C."Howies Fire Glow", C."Jenny Wren" and C.polandii at Kew. Many of the Queensland varieties, apart from the lovely red bottlebrush flowers, have spectacular pink to dark red foliage at various times of the year which is absent in most of the southern callistemons. Growers in warmer climates such as New South Wales and Queensland, who often have difficulty getting some of our southern callistemon cultivars to flower, might well consider growing them in large pots.

Reprinted from the May 1996 issue of the newsletter of the Society's Melaleuca and Allied Genera Study Group.

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Australian Plants online - June 1997
The Society for Growing Australian Plants