Most Banksias occur naturally in South West Western Australia; some species are also indigenous to other states and one to New Guinea. They belong to the Proteaceae family, most are shrubs but they do vary from low spreading ground covers to medium sized trees.
Banksias were named after Joseph Banks the British naturalist - the first European to collect specimens of these plants in 1770 after landing on Australian soils. (The voyage of discovery to Australia headed by Captain James Cook on ‘The Endeavour’).
Banks’ illustrator Sydney Parkinson illustrated the entire collection on the return voyage to England. The genus was later described by Carolus Linnaeus in his Supplementum Plantarum published in 1782.
In recent times many cultivars of this beautiful plant have been developed.
The number of species in existence varies according to different authorities; some claiming 73 others up to 90. All except B. dentata (which is also found in Papua New Guinea) are Australian - with 58 indigenous to Western Australia.
- Description: Banksias are easily recognized by their flower spikes - often referred to as ‘candles’ but actually known botanically as an inflorescence. The flowers are usually erect on the plant (but sometimes hang), and have a colour range from yellow, to orange and red and even pink. The centre of the flower head consists of a wooden axis that has a furry coating; the flowers appear in tightly packed pairs at right angles to the central wooden structure. The inflorescence is made up of hundreds to thousands of tiny flowers. Woody fruiting structures hold the black two-winged seeds after flowering.
- Natural habitat: Western Australia - mostly in the south west. In the eastern states mainly along the east and south eastern coasts and tablelands. They do not exist in rainforests or arid areas. Banksias grow on poor, sandy soil that is often not suited to other plants.
- Flowering time: varies but it is possible to find Banksias in flower at all times of the year
- Habit: bushes, trees and groundcovers
- Hardiness: varies, but WA types are often difficult to grow in the east
- Foliage: variable, mostly serrated
- Lifespan: long lived
Soil must be well drained for most varieties - particularly those from Western Australia.
Like most members of the Proteaceae family, Banksias do not tolerate poorly drained situations and most popular varieties prefer sandy soils. If drainage is likely to be a problem, try to grow them in raised beds, on mounds, slopes or in sandy soils. Even consider growing them in pots.
Banksias generally prefer an acidic soil, though many of the West Australian species grow on acidic top soils with alkaline sub soils. Such species are often difficult to grow in places outside Western Australia, unless they are either grafted onto eastern species (such as B. integrifolia or B. marginata); or grown on a soil where a sub surface layer of lime has been created over a top soil layer of well drained acidic soil. This is called the limestone underlay technique. Limestone underlay technique has proven useful to enable more difficult WA species to grow outside of their natural habitat.
It would appear that Banksia species prove difficult to grow in the eastern states of Australia or other parts of the world, partially because of higher humidity, (good ventilation is also a must - do not crowd them amongst other plants) and partially due to soil conditions as outlined above.
Success has also sometimes been achieved by using eastern species as a rootstock and grafting the WA species onto a root system that better tolerates wet and sometimes acidic soils.
- Do not feed with fertilisers containing phosphorus.
- Respond well to iron (place some rusty nails around plants).
- Do not over-water.
- Most are highly susceptible to cinnamon fungus (ie. Phytopthera cinnamomi)
PESTS AND DISEASES
Though Banksias are particularly susceptible to fungal diseases, pest problems are relatively little.
Cinnamon Fungus (Phytopthera cinnamomi) is perhaps the most serious problem. Most Banksias are highly susceptible.
Other diseases which Banksias are susceptible to include:
- other species of the fungus Phytopthera
- grey mould (or flower blight) - Botrytis cinerea
- shoot tip blight - Drechslera spp.
- Armillaria root rot
- Verticillium wilt
- damping off (in seedlings)
- scab or cork bark - Elsinoe spp.
- silver-leaf - Chondrostereum purpureum
- white root rot - Rosellinia spp.
- bacterial leaf spot
Pest problems though relatively few, can include:
- root knot (caused by a nematode)
- caterpillars (attacking the flowers or occasionally leaves)
- beetle damage to leaves
- birds eating seeds (mainly parrots and cockatoos)
- insects eating seeds
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