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Growing Banksias in Northern Victoria
Paul Kennedy
Six years ago Barbara and I sold our suburban home in Melbourne and went to live at Strathmerton. We had been growing banksias with some success in Melbourne, but the limitation of space, clay-loam soil and cooler climate made it difficult to grow the Western Australian species successfully.
Our land at Strathmerton consists of two 7.25 hectare blocks and it is the rear block that has the sand hills which are so important to growing the Western Australian species successfully. In between is a clay pan laid down in a subsequent geological period. There are also some loamy soils between the sand and clay layer. The average rainfall is 450 mm, but for the past six years the rainfall has been well below average.
The sand hills are 20m deep and were laid down millions of years ago when the Murray River entered the sea at this location. The sand is a light brown in color but is very pervious. In places there is some wind blown sand which can be impervious when dry. The pH is slightly acid being 5.5- 6.5. What we did not know was that even in the hottest of summers there is a moist layer of sand 1.5m below the surface. We have watched eucalypts grow slowly for the first three years and then grow rapidly once the roots have reached this moist layer. Humidity is low in summer which western banksias are used to.
Growing banksias on the sand hill initially was a challenge as we had to overcome the hot dry summers and deal with the lack of moisture which is never assured apart from the months of August and September. The first step was to study where each species of banksia came from and its climate and soil type. To grow Australian plants successfully the first rule is to grow them in soil as near as possible to the soil type to where they occur naturally. The second problem was how to water them without killing them. The answer to this lay in observing the local cut flower growers who only watered at night after the sun had gone down. During the summer the banksias get about a third of a bucket of water from the hose once per week on dusk. I doubt whether it gives the larger ones much benefit as their roots are probably already down into the moist sand layer. I heard recently that some banksias can put roots down to eight metres in depth. With the house constructed, the plantings began in earnest in 1996.
To date some 74 species and subspecies have been introduced into the garden. Most flower at about three years of age which is earlier than specified in the Banksia Book*. The other interesting note is that nearly all flowering specimens have set seed, which is great for future collection of seed. I do not intend to list all of the species that we are growing, but rather to look at some of the individual species and comment on our experiences selecting species from different zones around Australia.
The Eastern Species
Not many of these are sand loving, but prefer to grow in heavier soils. Initial trials with the Banksia spinulosa group growing on sand was not successful as they turned yellow with stunted growth due to the lack of sufficient minerals in the sand. However on clay-loam soils they grow quite well and need summer watering in this climate to keep them alive. The coastal forms of Banksia integrifolia, B.serrata and B.aemula all grow well on the deep sand averaging 1 metre of growth per year.
- Banksia ornata is very specific about soil type and will only grow on deep sand.
- Banksia marginata, B.saxicola, B.canei and B.oblongifolia grow well in clay-loam soils and prefer some shade as our summers are very hot.
- Banksia robur and B.paludosa prefer to grow in wetter soils, however once established are quite tolerant of dry periods.
The Western Australian Species
Generally these can be looked at under six zones marked by climatic differences and in some cases soil differences as well. I'll elaborate on some from each zone that I have growing in the garden.
 Perth and northern sand plains
About 19 species are found here on deep sands, sandy loams and lateritic soils.
- Banksia leptophylla var. leptophylla. A plant six years old in sandy loam has grown to 1.5 m by 2.4 m and flowers profusely for ten months of the year. It has grown so large that from now on many of the flowers will have to be removed to keep the plant healthy and not become leggy.
- Banksia candolleana. The deep serrated leaves are a feature of this plant as well as its rounded shape. The bright yellow flowers in July are on stalks about 15Omm long. Planted in deep sand it took three years to grow to 1.0 m by 1.5m and flower.
- Banksia telmatiaea. Another that is being grown on deep sand At four years old it has grown to 1.3m by 2m and continues to flourish. The flowers are hidden inside the bush but are quite pretty to look at. Flowers for a long period from May through to November.
- Banksia laricina. This species has lovely dainty lime yellow flowers hidden in the bush. The foliage is also quite appealing in that it has light green terete leaves and is very dense. Flowers in winter on deep sand. The plant is three years old and 1 m by 1 m in size.
The southern forests
The soils here can very from sandy loams to clays and there is a much higher rainfall.
- Banksia cuneata. One of my favorites, although in some ways it looks more like a Dryandra than a Banksia. I have two plants growing on deep sand and one is now 3.6m high in four years Flowering now for the second time its open foliage allows the flowers to be easily seen. As it is endangered in the wild we should endeavour to grow as many as we can of this species.
- Banksia occidentalis. This species needs to be near moisture to survive. When I was visiting Cape Arid NP recently, I saw this species growing near wet depressions with populations kilometres apart. The two plants here are on deep sand but are also close to the fernery which has a watering system, so there is moisture available both artificially and naturally at depth to keep them going. Now 2.1 m high after four years, they flower in summer-autumn with red flowers.
- Banksia quercifolia. I have included this species because its flowers are a bit different to many of the other banksias. The cylindrical brown flowers grow along the stem and look quite attractive against the bright green foliage. Planted on deep sand it flowers in the winter here. Would probably grow well in loam soils provided moisture is available. Comes from forest areas.
I also have Banksia seminuda and B.littoralis growing in deep loam soil and they are growing at 1 m per year at present. Located near the shaded house, they receive some moisture at depth from the watering of seedlings.
The Stirlings - Albany zone
About eleven species can be found here on soils varying from shaly hill sides to grey sandy soils of the flatter areas.
- Banksia coccinea. Everyone wants to grow this one, however it generally is difficult to keep going. My observations in the wild have been that it tends to grow on shaly slopes where moisture is moving down the slope underground. I have planted two near the fernery in dappled shade and one is about to flower. It has taken me thirty years of trying to reach this stage.
- Banksia aculeata. This species has dark green serrated leaves and dark red pendant flowers hidden in the bush. It has fascinating seed capsules the size of a football in some cases. Grows only in the Stirling Ranges on sandy loams. Here it is on similar soil and tends to grow into a low bush rather than the tall forms you see in the Stirlings. Has flowered once in 1999 at the age of three years.
Geraldton - Kalbarri zone
There are five species in this zone all of which grow on deep sand.
- Banksia victoriae. Very striking when in flower as the pink- white flower is held on long stems. Planted in deep sand our specimen has grown to 1 m by 1 m in three years and flowered in January of this year. I'm looking forward to when it is a large plant with perhaps fifty or more flowers.
The dry inland zone
I have placed seven species in this category. They grow on deep sand to stony soils where rainfall can be very low and unpredictable.
- Banksia ashbyi. A very attractive species with bright orange flowers held high on long stems. Loves to grow on deep sand and does not like our cool winters. Nevertheless our specimen has reached 1.2m in height and flowered this winter. Frosts tend to burn off flower buds or deform them.
- Banksia benthamiana. The Perth members of the Society find it difficult to grow this species. It comes from the Meekatharra area where it grows in soils of clay and stone. I have 5 specimens growing and three are in clay loam soils and the other two in deep sand. The former have been outstanding growing quickly to 1.5m and flowering from the age of two years. The yellow -brown flowers are quite attractive and appear from December through to February. The plants have never been watered artificially as they seem to prefer dry conditions. The two on sand have grown much more slowly and have flowered also. However I think the right soil type has a lot to do with successful growing of this species.
- Banksia laevigata ssp fuscolutea. Another very interesting plant in flower. Grows naturally north and east of Lake King on loamy soils over laterite. Planted in loam here it has grown to 1 m by 1 m in three years and flowered profusely in the past two years. Does not prefer to be artificially watered. The striking aspect of this banksia is the tennis ball shaped flowers which commence as woolly brown flowers and change to deep yellow with age. Flowers in autumn.
The southern sand plains
As the title suggests, this includes the coastal areas from east of Albany to east of Esperance. There are about seventeen species in this area, most of which grow on sandy soils although some are to be found on the stony soils of the Barrens. Also the ironstone/laterite soils on the Ravensthorpe range.
- Banksia speciosa. This species loves our climate and sand hill. In three years it has reached 2.4m in height and flowered in its second year. Its roots have probably already reached the moist layer in the sand and from now on the battle will be to keep in some reasonable size and shape. The flowers are on long stalks and make good cut flower specimens for indoors.
- Banksia epica. One of the rarer species which grows in sand on the edge of the Great Australian Bight. Few people have seen this one because of its remoteness. I have four plants growing here and they appear to have settled in. The flower is similar to Banksia media.
- Banksia blechnifolia. A prostrate species that has spread rapidly over the ground. Each year the number of flowers produced increases and this year I can count about fifty orange- brown spikes The deeply lobed bright green foliage is also quite attractive. I like to mix taller and prostrate banksias together if they are growing in a garden bed.
Well that is the end of the species that I'd like to comment about. Now for the list of banksias that I need seed or seedlings of. I hope some of the Banksia Study Group members (or others) can help so that the banksia collection can be established here.
Banksia conferta ssp penicillata, B.lindleyana, B.elegans, B.goodii, B.leptophylla var. melletica, B.verticillata, B.meisneri ssp ascendens, B.paludosa ssp astrolux, B.pulchella, B.nutans var. cernuella, B.oligantha.
I hope these above notes are of some help to readers in growing banksias. The sharing of information is vital if we are to move forward in the successful growing of this wonderful genus.
From the newsletter of ASGAP's Banksia Study Group, March 2003.
* The Banksia Book by Alex S George, Third Edition, 1996. Kangaroo Press.
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Australian Plants online - June 2003
Association of Societies for Growing Australian Plants
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