Banksia seminuda: River Banksia

Discovering Banksia seminuda

Banksia seminuda, a little known Tree commonly known as river banksia that is under used in Gardens.

This is a Banksia that I first saw in a book about 10 years ago. I found it interesting right from the start because it was one of the few banksias that grow into a tall tree. It had a narrow upright habit and also had bright yellow Banksia type flowers. 

The other thing that interested me was the fact that in its natural habitat in Western Australia, it grows near rivers and streams which made me think that it may survive in heavier soils that weren’t so well draining. Maybe!

Growing Banksia seminuda

Most Western Australian Banksias grow in sandy or gravelly soils that are very well drained and as a consequence don’t do very well in conditions that are different to those in their natural habitat.

This Banksia though, I thought might be a bit more versatile. Over the years I’d always kept an eye out for one in nurseries but it wasn’t until about 3 years ago I came across some at a native plant market.

Of course you can guess I did buy one and decided to plant it in the back corner of my garden. This was the obvious place I knew it was meant to be not only fast growing but in its natural habitat it was meant to grow up to 25 m in height. The funny thing about it though when I did plant it, I didn’t really expect it to live all that long. 

As I said, in its natural habitat, it grew next to rivers which indicated to me that it may not be very drought tolerant and secondly the place where I planted it had very little topsoil and had a heavy clay base just a few centimetres below. So when I planted it I didn’t hold much hope for its survival.

River Banksia Growth Rate

Well as time went by the first thing that I discovered was that it was in fact quite a quick grower. The first year it grew to about 2 m in height and this was with very little rainfall or other watering by me.

The other thing that I discovered was that the phosphorus in the soil hadn’t affected it adversely at all. Now as I write this post it has just come through its third summer and is now just over 3 m tall.

The amazing thing about this summer was that it was extremely dry. There was very little rainfall and the melaleucas growing in the vicinity are starting to send their roots into its root zone so the competition for the little moisture in the ground is quite fierce.

Despite this, it has still continued to grow without any watering from me and has survived some very hot dry days over summer including 4 days in a row where the temperature got over 40°C as well as another day when the temperature got as high as 46°C.

So what more can I say about this tree. It appears to be a very drought tolerant plant, grows fairly quickly, isn’t affected by phosphorus toxicity and appears to tolerate soil conditions that are different to its natural habitat.

The other amazing thing is that you never appear to see it in nurseries, even the specialist native nurseries. At this stage I’m prepared to give it the thumbs up and say it deserves to become more mainstream.

So if you ever see it for sale somewhere and feel like you may be able to find a spot for it in your garden then please give it a try and let me know how you go.

Banksia seminuda Flowers

Banksia seminuda is a tree that can grow up to 25 m in its natural habitat growing alongside streams in Western Australia. Unfortunately though, it is rarely seen in cultivation as it does have some very desirable features such as its adaptability to different soil types, its reasonably fast growth rate and of course its orangey yellow flowers (also yellow varieties as well).

I’ve personally got two Banksia seminuda growing in my garden, one about 4 years old and the other about 3 years old. Neither has flowered at this stage but this is not unusual as most seed grown banksias can take between 3 to 10 years before they flower.

In the case of Banksia seminuda, it is normally about 7 years and this was the case for Steve Bromley in Tasmania who’s 7 year old Banksia seminuda has just come into flower for the first time.

Steve kindly sent me some photos which I thought were well worth publishing especially since this fantastic Banksia is so rarely seen in people’s gardens.

Hopefully my Banksia seminuda will continue to thrive. I’ll keep my fingers crossed and keep you informed.