Banksia Marginata-many growth forms



common colour of Banksia marginata flower

Banksia marginata or silver Banksia Banksia marginata Pdf is perhaps the most variable of all the banksias found in Australia.

In Tasmania it can be found from coastal areas to alpine areas at 1200 metres above sea level.

It can be a prostrate shrub in coastal areas such as Cape Pillar or a small shrub in alpine areas or a tall shrub/small tree in open woodland or wet forest as on the Gordon River in the Vale of Rasselas.
This species may posses a lignotuber or have no lignotuber at all and both can be found in a single population growing next to each other.

The leaves of this species are  extremely variable and can be linear,oblong or narrowly wedge shaped/lance shaped with entire margins or even serrated margins. The leaf tip can be either blunt or have a distinct point.Leaf size is also extremely variable from 1 to 10 cm long and from 3-20 mm wide.
The upper side of the leaf is dark green and the underside of the leaf is white and quite hairy.

The flowers of this species are usually a golden yellow colour but they can also be green,rusty brown or even pink from 3cm long up to 20 cm long on some sub alpine forms..










Unusual flower colour on Banksia marginata at Drip Beach near Cygnet

 The Royal Tasmanian Botanical Gardens in Hobart has a number of different forms in its collections,in particular there is a bed planted out with mainly low growing forms of  Banksia marginata near their Visitor Centre at the Greater Hobart Garden and the French Memorial Fountain.

The Gardens has the following Tasmanian forms,Mini Marge,Coastal Spread,Petal Point Prostrate,Cole's Bay Compact and selections from South Arm and South Port Bluff.



Banksia marginata forms bed at the Royal Tasmanian Botanical Gardens



South Arm selection of Banksia marginata at the Royal Tas Bot Gardens



Below is a list of localities in the state that I have noticed particular forms :

Cape Pillar-The far tip of Cape Pillar has some of the best forms of Banksia marginata I have seen in one location in Tasmania. There are forms that are totally prostrate and forms that are miniature and everything in between. I have propagated a number of these from seed and I hope to discover whether it is the environment that is causing these forms or whether it is genetic, please see images below :

 

 

Prostrate form of Banksia marginata at Cape Pillar

Pink flowered form of Banksia marginata at Cape Pillar





 

Mount Wellington-There are several  bushy subalpine forms on this mountain that grow up to 3 metres and have large flowers up to 15 cm long,see image below



Mount Wellington sub alpine form

Bay of Fires/Gardens
This area of North Eastern Tasmania has a number of miniature and low growing forms of Banksia marginata which aren’t in cultivation yet.

Southern Forests

This area south of Hobart has forms with linear leaves and looks very similar to Banksia spinulosa if you look at it from a distance, I discovered a couple of specimens that had good horticultural potential but as they were in State Forest the area was logged before I could propagate them, please see image below

Image of Southern Forests form



 Denison Range-There are several very bushy forms found on this range that never get more than 2 metres tall by up to 3 metres wide,see images below :

Bushy form of Banksia marginata growing on the Denison Ranges



Harts Hill Reserve-I recently discovered a low growing  form  40cm tall by 1.5 metre
wide and another form that is 1.8 metres tall by 2 metres wide in this reserve please see images below
:



Harts Hill bushy form of Banksia marginata



Harts Hill low growing form of Banksia marginata

Cape Raoul
This area has forms very similar to Cape Pillar,but they appear to be more upright than the very prostrate forms on Cape Pillar.

Prostrate form of Banksia marginata at Cape Raoul

Green flowered form of Banksia marginata at Cape Raoul

Petal Point-This area in North East Tasmania has many interesting forms of Banksia from low bush forms from one sold by Pulchella Nursery at Buckland that is nearly prostrate See image below :


Petal Point prostrate form growing in our garden.



Lovely new growth on Banksia marginata at South Bruny National Park



Cultivation
In cultivation this species needs a well drained acid soil in full sun or part shade.
Banksia marginata will tolerate drought and extremes of temperature  once established,depending on the provenance of the parent plant.

Banksia marginata responds well to a light feed of Blood and Bone or a similar low phosphorus fertiliser in spring and Autumn.

Propagation

Banksia marginata is easy to propagate from seed ,although you may need to stratify the seed if it comes from alpine environments.I have observed that seed collected from Banksia marginata in Alpine/ subalpine  environments are more prone to damping off then seed collected from lower altitudes,I am not sure why this is  yet as I treat all seed the same,will keep you up to date if I discover why this is so.

Banksia seed should be sown in a well drained seed mix designed for natives,in either a seedling punnet or a  small square pot as drainage is critical if you are to avoid damping off,a fungal disease caused by poor drainage and lack of air movement.

Some Banksia seedlings also seem prone to  Chlorosis,which shows up as a yellowing of the leaves,this can be corrected by applying iron chelates.

Seedling showing signs of Chlorosis

Seedling from Cape Pillar Prostrate form that seems to becoming true from seed.

 Banksia seedlings germinating in a seed punnet

Propagation from cuttings is recommended if you are trying to propagate a particular form,semi hardwood cuttings in late summer/Autumn are recommended but sometimes are slow to strike so be patient...