AusBonsai

Hi everyone

Looking for confirmation that this is B. Marginata. Growing on north head near manly. Some bushes there were up to 3m.

Thoughts?

Squizzy

I've never been able to be 100% sure because marginata and integrifolia seem to sometimes share some of the key attributes. I believe that the blunt/ square ends of leaves shown in these photos indicate B. marginate so happy to agree with your ID.
3m is well within B. marginata size range.
Note there is debate amongst botanists about whether B. marginata is a single species or several closely related species. Some marked differences between inland and coastal forms.

Cheers for the thoughts Neil. Yeah I am only confused because the marginata I have seen have had some spikes on the ends of the leaves. In saying that I have seen integrifolia growing in coastal conditions with smooth round leaf ends. I wonder if it’s something to do with salt air or wind. Or possibly something to do with not needing spikes to fend of animals in that location. Amazing adaptation really. Serrata in the same area are loaded with serration.

Squizzy

So to clear up my confusion. These are stems and leaves of marginata I bought from a tube stock nursery last week. As you can see they are distinctly different to the plants at north head.

Squizzy

The last photos are typically marginata with the square leaf ends. The original pics show some blunt and some rounded ends so you could go either way with those.
As mentioned, B.marginata has a wide distribution and also seems to have a range of characteristics so there are many different forms. So much so that the botanists were considering splitting it into several new species.
When ID gets hard like this I just don't worry too much. It is certainly a Banksia and, whichever species it is general treatment will be the same.

Thanks Neil

Just checking I hadn’t missed a new species. I can see why they might want to split them. I have had trouble growing marginata as bonsai but none at all growing integrifolia. I must work out why. Anything obvious you can say from your experience?

Squizzy

New species is always a possibility. The botanists need to look a bit closer now but still identifying new ones.
National herbarium (Melbourne) now charges a fee for ID but I believe some other institutions are still offering the service. Check with some of your local plant based institutions - botanic gardens, herbarium, etc to see if they are interested in receiving samples.

I also had a lot of trouble with our local form of B. marginata. All eventually dead. Tried again with the Tas form and they seem to be doing much better. Either my knowledge and technique has improved in the meantime (likely) or this new var has different characteristics that make it more amenable to my gentle ministrations.
My advice: try different forms and sources. There is always a range of genetics in any population so it may just be a matter of finding 'the one' that matches our cultivation.

The B marginata I have grown all seem to prefer low humidity, ie away from the coast. They were a bit patchy in the southern highlands even in pot culture but do fine in the dry and hot climate of Canberra.

Grant

Thanks Grant

It’s got me stumped this humidity thing though. You would have to assume salt air on a headland next to the Pacific Ocean is fairly humid. These plants seem to be powering. I’d imagine they are naturally occurring here. Maybe it’s a seed variant that’s worth pursuing.

Squizzy

These may be just a few of the differences between coastal and inland forms of B. marginata. Anther noted differences are that inland forms generally regenerate from the stems and lignotuber after fire while coastal forms are killed by fire and rely on seed to regenerate.
There are usually distinct collars between yearly growth cycles on our inland form. You can actually count how old a tree is (up to about 10 years?) by following back down the trunk. Not sure whether that occurs on coastal forms?