banksia proteoid roots

Summer is also time for repotting many of our Australian native plants. I was repotting some banksias and came across this interesting phenomenon.

We hear so much about Australian Native plants being allergic to phosphorus and needing very careful fertilising. the truth, however, is that only a very few Aussie natives are sensitive to phosphorus and there are also a few plants from other parts of te world that are phosphate intolerant as well. I give most of my Australian natives the same fertiliser that I use on the exotics and they grow very well on it.

The exception is Banksias and here is the reason

proteoid roots on banksia

That white patch that looks like fungus is actually a patch of specialised roots called proteoid roots that have evolved in some of the proteacea plants to help them extract phosphorus from the nutrient poor soils they tend to live in.

a closer look



Looking a bit closer you can actually see the hundreds of tiny white root tips that are all collecting every available scrap of phosphate from the soil.
And that is the problem. When we apply phosphate rich fertiliser these tiny, super efficient phosphate absorbers continue to grab all the available phosphate. That results in a phosphate overdose and  a very quick death for your banksia so be quite wary of what sort of fertiliser you give to your banksias.
Banksias do not NEED proteoid roots and when they are in an environment that has adequate phosphate in the soil they do not develop these special roots. If we slowly incease the amount of phosphorus in the soil the tree will gradually shed any proteoid roots and can then tolerate normal amounts of phosphate fertiliser but as soon as the nutrient levels drop off again the plant will again grow more proteoid roots and will be sensitive again.
When repotting banksia bonsai most of the proteiod clusters are cut off but that will not hurt the tree any more than normal root pruning hurts any other species.
I do not want to give the idea that banksias can grow without any fertiliser. When grown in a pot nutrients are quickly leached out of the potting mix by regular watering so even banksias need regular fertiliser but its best to play it safe and use a low P formulation.
Many of our banksia species make excellent bonsai. They will shoot on old wood when pruned, They tolerate root pruning very well (in the warmer months) and continue to thicken even in the cramped confines of a bonsai pot so try some banksias for bonsai, just be careful what you feed them.

Is it too late to repot my…..?

This question is regularly asked by beginners in bonsai. The answer given is usually along the lines of ‘repotting deciduous species must be done as the buds swell and before the leaves open.’

For many years I have stuck with this repotting rule but recently have started to question its validity. Sure it works but is it entirely accurate? Some new information has indicated that this rule may be far more prescriptive than necessary. Continue reading

Repotting Aussie natives

I love bonsai and I’m also passionate about Australian Native Plants so it was natural for me to try to grow Aussie natives as bonsai. Originally I tried to use the Japanese timing and techniques and had many abrupt failures so gave up on natives as bonsai for many years. More recently, information from committed growers has led me back to growing natives as bonsai. Word was spreading that many of our natives dislike having roots pruned in the traditional winter/ spring period but thrive when repotted during the summer. Several years ago I set out to confirm this with a series of trials. Continue reading

Root pruning and repotting

Bonsai grow in the confined space of a relatively small pot. The roots of all plants keep growing to renew the active root tips that actually do the work of absorbing watera nd nutrients. After a couple of years these constantly growing roots have so filled the spaces in the potting mix that vital air and water cannot enter the mix and the tree will not stay healthy. It is very important to repot bonsai (and indeed, all potted plants) regularly to keep them healthy. Root pruning does not keep a bonsai small. In fact just the opposite. After rootpruning and repotting in fresh mix with new nutrients and room for new roots to grow we usually see an explosion of growth for the first year. The picture in this post will give a good idea of how I root prune and repot deciduous bonsai. Continue reading


It is June at Shibui Bonsai and that means winter. We have had a few light frosts so far this season but this morning was probably the coldest yet.

Frost on a trident maple

Here in Australia we do not have to contend with really severe cold that growers in some other areas get. My cold hardy trees stay outside without any protection all winter without any ill effects, in fact I think it might even be good for them. Low temperatures help to induce some trees to flower better and I hope that some of the pests and diseases will also be killed during cold weather. My ficus, which are NOT cold hardy, live in the unheated poly igloo which provides enough protection to get them through the winter here.  Continue reading