Banksia

 

Visitors to Empress Josephine’s garden at Malmaison outside Paris were wowed by her banksia collection. 


Two hundred years later gardeners still thrill to these bold and beautiful flowers, but have cold feet about growing them. Graham Ross explains why, and reports on the new cultivars now available.

 

While every Australian gardener is familiar with banksia, few of us actually grow them, which is a great pity. Perhaps we have been influenced by May Gibbs and her ‘big bad banksia men’. The renowned children’s illustrator and author of ’Snugglepot and Cuddlepie’ first noticed the malign nature of aged banksia flowers when out walking near her childhood home in Western Australia. "I was out walking, over in Western Australia, with my cousins," she told the National Library of Canberra. "We came to a grove of Banksia trees and sitting on almost every branch were these ugly little, wicked little men that I discovered and that's how the Banksia Men were thought of."

 


Low-growing Banksia spinulosa flowers simultaneously with happy wanderer (Hardenbergia violacea). Photo - Gerry Whitmont/photolibrary.com

 

Do generations of Australian children now harbour bad feelings towards banksias? Or do so few Australian landscapers brave banksias for fear of phytophora fungal root disease and the plant’s perceived intolerance of heavy clay soils? Banksias originate in a wide range of soil types and climatic conditions so the right match can be made for your garden, whether it’s coastal, inland, damp or dry, but only if you do your research first.

One of the first gardeners to get a thrill from the banksia’s unusual, bold flowers was Empress Josephine. Napoleon’s wife had a magnificent garden at Malmaison, where she cultivated plants from all over the world, including many from Australia. Between 1799 and 1814 there were more than 100 Australian plants in the gardens at Malmaison, outside Paris, including grevilleas, wattles, tea-trees and banksias. And while Josephine also had black swans, white cockatoos and emus in her park, she had none of the other birds that are mad for banksias.

Banksias are a great lure for native birds. The abundant nectar on the candle-like spikes of flower draw nectar-eating birds, such as New Holland honeyeaters, as well as nectar-loving insects. The insects in turn attract birds such as fantails and thornbills. Later in the flower’s lifecycle, the seeds attract larger birds including parrots and cockatoos.

 

Lorikeets flock to feed on banksia nectar. Photo - Anne Montfort/photolibrary.com

 

 

Banksias in the garden

Australia lays claim to 77 of the 78 banksia species; the exception being found in Papua New Guinea. The majority of our 77 species are native to southwest Western Australia and most of these cannot cope with the East Coast’s humid conditions. The humidity provides an ideal environment for the spread of the root rot fungus, Phytophthora cinnamomi, to which western banksias are particularly sensitive. Some species, such as Banksia speciosa, appear to grow quickly and thrive for a couple of years, only to cause distress to their gardeners by dying rapidly over a single summer.

Banksias are used to well-drained sandy soils or sandy loams and sunny positions. If your soil is heavy or drainage poor, look for Banksia integrifolia or Banksia robur. Some forms of Banksia spinulosa are found naturally on clay soils in the Sydney basin, but be prepared for slow growth.

 


Banksia serrata seedpods persist on the tree indefinitely. Photo - Linda Ross

 

To improve soils to banksia-friendly condition, add gypsum or other soil conditioner or raise the soil level into a mound at least 30-60 cm above the pre-existing level. Banksias appreciate extra water during dry periods, especially during summer. Special care should be taken not to let them dry out until established. They will eventually put roots deep into the ground and find the water table, but the process may take up to two years.

Fertilising with phosphorus should be minimal. A slow-release, low-phosphorous treatment is best. If new leaves turn yellow use iron chelate or iron sulphate according to the instructions. Species that grow from lignotubers, a group that includes Banksia robur, B. spinulosa and B. serrata, may be pruned hard - even back to ground level. Others, including B. ericifolia and B. ‘Giant Candles’ are nonlignotuberous and should be pruned lightly (not below green foliage) after each flush of flowers. This prolongs the life of the plants and keeps them compact.

In recent years some nurseries, plant enthusiasts and members of the Australian Plant Society have turned their attention to breeding new banksia hybrids and grafting techniques have made it possible to grow banksias in varying soil types. Some species have been grafted onto fungal-resistant eastern species. Combinations to look out for include Banksia brownii on B. integrifolia and B. speciosa on B. aemula.

 


Banksia spinulosa 'Birthday Candles'. Photo - Linda Ross

 

Groundcover banksia

The Mt Annan Royal Botanic Gardens, south of Sydney, has a good collection of prostrate banksia species that excites and surprises visitors. One of the most impressive is B. blechnifolia, the fern-leaf banksia. We see marvel at this groundcover with its 5m spread on our wildflower tour of WA. The plant’s red, spring growth is magnificent but is eclipsed by the erect, 20cm tall, cylindrical spikes of pinky-red flowers. It is ideal on embankments, between rocky outcrops and in half-barrel tubs. Easy options for the less-experienced city gardener include some of the named banksia groundcovers:

Banksia spinulosa ‘Birthday Candles’, grows 50cm high to 1m wide with a fine display of golden yellow flowers. It is excellent as a tub, rockery or garden specimen. It will survive light frosts and needs no pruning.

Banksia spinulosa ‘Honeypots’, is similar to ‘Birthday Candles’ but grows a little wider and features orange-yellow flowers.

Banksia spinulosa ‘Stumpy Gold’, grows 30-40cm and 1.5m wide with yellow flowers up to 40cm tall. It will survive light frost and needs no pruning. It is an excellent groundcover, potted plant or landscape plant.

Banksia serrata ‘Pygmy Possum’, is a naturally occurring, dwarf, coastal banksia, growing only .5m tall and 2.5m across with upright 12cm tall greyish yellow flowers.

Leaves are stiff, dark green and serrated as is the parent, the Old Man Banksia. Moderately frost-resistant.

Banksia integrifolia ‘Austraflora Roller Coaster’, grows as a 20cm thick shagpile carpet to a width of 2.5m with masses of lemony yellow flowers. Its parentage ensures good growth in seaside gardens or in hot arid conditions. It’s ideal on embankments, spilling over half-barrels or as a groundcover in full sun. Unfortunately it’s hard to find in nurseries but worth chasing.

 

Where to buy

Sydney Wildflower Nursery

9 Veno Street, Heathcote

www.sydneywildflowernursery.com.au

tel: (02) 9548 2818

  

Plant notes: easy banksias


Coastal Banksia

Plant name: Banksia integrifolia

Description: the easiest banksia as it will grow in most soils, even alkaline ones. It is a fast growing plant of open, rangy habit and can grow into a large tree.
Size: 6m x 2m
Special comments: the prostrate form, ‘Austraflora Roller Coaster’ remains prostrate. Leaves are serrated on young plants, entire on older. The yellow flowers occur in autumn, and forms have greenish buds. In Sydney, the local form is integrifolia, which the form most commonly seen in nurseries.

Conditions:
Full sun
Drought hardy
Frost tender
Climate map: warm temperate, subtropical, tropical 

 

Photo - Dan Rosenholm/photolibrary.com


Old-man Banksia

Plant name: Banksia serrata 

Description: occurs in coastal regions from Queensland to Tasmania. Large flower spikes in summer-autumn, are grey-green in bud, turning yellow. Large eye-catching woody cones. Slow-growing but long-lived and may take several years to flower. It has attractive foliage and develops a gnarled warty grey trunk over time. Especially good for exposed coastal sites.
Size: Grows 10 to 12 m high.
Special comments: a prostrate form known as B. ‘Austraflora Pygmy Possum’ is available. Banksia aemula is similar but leaves are smaller and flowers brighter. Its fruit is the "Big Bad Banksia Man" of May Gibbs' stories. Both are fairly finicky about soil, preferring a sandy, well-drained, sunny site.

Conditions:
Full sun
Drought hardy
Frost tolerant
Climate map: cold & warm temperate, subtropical, tropical

 


Photo - Linda Ross

 

The Swamp Banksia 

Plant name: B. robur  

Description: spreading shrub with very large, leathery leaves with serrated margins up to 30cm long. New growth is colourful, in shades of red, maroon or brown with a dense felt-like covering of brown hairs.
Size: 2.5 metres
Special comments: stunning large flower spikes, metallic green with pinkish styles in bud, becoming cream-yellow and fading to brown. Likes plenty of moisture.

Conditions:
Full sun
Part shade
Frost tender
Climate map: warm temperate, subtropical, tropical

 


Photo - Suzanne Long/photolibrary.com

 

The Hinchinbrook or Blue Banksia 

Plant name: Banksia plagiocarpa 

Description: from North Queensland, this banksia grows readily in Sydney. It is related to B. oblongifolia and has more vivid, furry, red new growth. The other outstanding features are the spikes, which are generally blue-grey in bud.
Size: 4m
Special comments: Hinchinbrook gets a lot of rain so this plant would appreciate extra moisture and prefers sandy soils.

Conditions:
Full sun
Part shade
Frost tolerant
Climate map: warm temperate, subtropical, tropical

 


Photo - Linda Ross

 

Hairpin Banksia 

Plant name: B. ericifolia 

Description: found in the Sydney Basin and Blue Mountains on sandstone soils. A strong-growing, bushy shrub with long red-to-orange spikes with red styles. Some forms, such as 'Kanangra Gold' have paler orange spikes with gold styles. It flowers in late autumn and winter and is very attractive to birds. Plant in sandy soils and don't prune hard.
Size: showy shrub 1-3 m by 1-2m
Special comments: flowers over a long period through autumn and early winter with spikes from yellow to orange, and styles of yellow, orange, red, pink, maroon or black. The subspecies most commonly seen in nurseries is variety collina (Hill Banksia).

Conditions:
Full sun
Part shade
Drought hardy
Good for pots
Frost tolerant
Climate map: warm temperate, subtropical, tropical

 


Photo - Linda Ross

 

Text: Graham Ross

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Author: Graham Ross