After the heat, there’s the rain
After some very hot days, the rain has come and the temperature is starting to assume autumn- like coolness.
Banksia marginata (or silver banksia) has been spot flowering in some places since February but is now flowering in earnest. Silver banksia – so called because of the silvery, velvet under surface of the leaves – can be found alongside many of the main tracks in the Reserve. The plant is quite variable in appearance although is mostly around 1m to 1.5m in height here. The leaves are around 6cm long and 3 to 8mm wide mostly without marginal teeth, except in the juvenile form, and with a notch out of the end.
The DPIW (2008) in Tasmania points out that “banksia marginata, like many other banksia species, has a distinctive annual branching pattern, with small, circular swellings formed at the junction of each annual growth increment. It is possible to estimate the age of individuals by counting the swellings, or nodes, each representing one year of growth. Banksia marginata survives up to 150 years.”
Like those of the sliver banksia, the leaves of the hairpin banksia are darker green on top and have a silvery, velvet -like underside. They are also longer and finer, up to 12cm long, and have marginal teeth all along the sides. The plant is also generally taller. It is likely that the variety in the Reserve is banksia cunninghamii– because of the shape of the leaves (those of the variety spinulosa are smoother and finer) and the habit (generally taller than spinulosa, up to 6m). Notably, unlike spinulosa, cunninghamii does not have a lignotuber. This means that it relies on seed germination for renewal after fire.
The flowers of the banksia varieties are somewhat different. Those of the silver banksia are more yellow to lemon coloured with longer yellow styles that stick out beyond the flower. Those of the cunninghamii have black or red styles sticking out beyond the orange flower cones. The cones of the hairpin banksia are longer than those of the silver banksia.
One of the characteristics of the banksia is their ability to survive in very nutrient-poor soils. This is because they possess “clusters of roots (proteoid roots) that exude substances called carboxylates in and around the root zone. These substances make nutrients, particularly phosphorus, more available to the banksia plant” (DPIW, 2008). They can also tolerate a range of environmental conditions and soil varieties. Silver banksia is “unpalatable to wildlife, which allows for higher seedling survival rates. Fire plays an important part in its ecology, stimulating both reproductive and vegetative regeneration, with a distinct burst of regeneration following a fire” (DPIW, 2008).
Banksias are bird pollinated but also by insects and small mammals but not by the wind (Collins, Collins & George, 2009).
Sources and further information
Australia National Botanic Gardens (2012) Banksia marginata. Found at http://www.anbg.gov.au/gnp/interns-2012/banksia-marginata.html
Australian Native Plants Society (2007) Banksia cunninghamii. Found at http://anpsa.org.au/b-cun.html
Australian Native Plants Society (2007) Banksia marginata. Found at http://anpsa.org.au/b-mar.html
Australian Native Plants Society (2007) Banksia spinulosa. Found at http://anpsa.org.au/b-spi.html
Collins, K., Collins, K. & George, A. (2009) Banksias. Bloomings Books: Melbourne.
Corangamite Seed Supply & Revegetation Network 2005 (2006) Banksia marginata Silver banksia. Found at http://www.florabank.org.au/files/documents/provenance/20070801-12.pdf
Costermans, L. (2009) Native trees and shrubs of south-eastern Australia. Sydney: Reed New Holland
Department of Primary Industries, Parks, Water and Environment, Tasmania (2008) Banksia marginata. Found at http://www.dpiw.tas.gov.au/inter.nsf/Attachments/LJEM-7CV6CA/$FILE/Banksia%20marginata%20Notesheet.pdf
The Royal Botanic Gardens and Domain Trust (2011) PlantNET – The Plant Information Network System of The Royal Botanic Gardens and Domain Trust, Sydney, Australia. Banksia cunninghamii Sieber ex Rchb. Found at http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Banksia~cunninghamii