Banksia Development Help

[Mickeyjaytee]

Hi all,

I picked up a small Scott’s River Banksia and thought I might give it a shot for bonsai. It has nice small leaves similar to B. Ericifolia.

I had 2 questions regarding banksias. The first, it seems with a few banksia species and, definitely the Scott’s river banksia, is that they have points along the trunk where 4 branches come out similar to a pine. Is it best to remove them leaving one or leave them for now seeing the plant needs many years growing yet.

Secondly was the roots. They were so fine, I couldn’t separate the roots from the soil. Instead masses of roots came away with the soil so, I only took off a little. Does this make it a bad specimen or do other banksias do the same?

I do know of proteoid roots and how some banksias have those and other thicker “normal” looking roots but, this tree only had the very fine roots. Maybe it’s just too young at the moment.

Anyways, any help would be appreciated. I know very little about banksia bonsai and would love to give them a try.

[shibui]

All the banksias I've worked with have those very fine, matted roots. It is real hard to cut them with the root shears but they are quite brittle so I usually just grab a handful and break it off to root prune. This approach does not seem to bother the trees.
They do develop some thicker roots eventually but still retain those very fine feeder roots as well as proteoid roots when they experience low P.
The dense, fine roots can be a problem as they fill the pots, often in just a single year. The roots also seem to be a bit hydrophobic. Initially I lost a lot of trees through spring which turned out to be because the pots were so choked with roots that not enough water could penetrate and the trees gradually got drier and drier as the weather warmed up despite watering as thoroughly as possible. I now like to root prune young banksias each spring to make sure there's fresh potting mix and room for water through the coming summer.
The species I've worked with have no problem with root pruning and I've had no problem removing up to 80% of the roots at repotting if it is done during warmer weather while the plant is active. You might like to be a little more conservative when working with new species as I have found with Melaleucas that not all species in the family manage the same treatment.

Re branches: The whorls of branches is a common trait with most Banksia species. They will definitely swell the trunk at that point. Whether you remove some depends if you intend to use that section of trunk. Sacrifice branch/trunk is used to thicken the trunk so often the lowest branch will be used as the main trunk of the final bonsai. Anything above that is redundant. Remove extra branches at whorls if you intend to use that part of the trunk in the final design.
Different species respond to pruning differently. B. integrifolia and B. serrata both bud on old wood abundantly, like ficus so I can chop trunks almost anywhere and expect plenty of new shoots. Again, check how each species responds before committing to chopping to bare wood.

[treeman]

The roots also seem to be a bit hydrophobic. Initially I lost a lot of trees through spring which turned out to be because the pots were so choked with roots that not enough water could penetrate and the trees gradually got drier and drier as the weather warmed up despite watering as thoroughly as possible.

You don't use wetting agents?

[Mickeyjaytee]

Thanks mate, I always appreciate your input. Really interesting stuff about the first branch eventually becoming the trunk. I’ve never thought of that. Is that common with all bonsai or mainly banksias?

I won’t stress too much about the roots atm. Lots came off and the plant is fine and happy. Banksias seem like a good choice for me!

I will definitely keep an eye on the roots filling the pots. After my last few adventures I’m already on high alert.

I’ve always been curious to know what people think of wetting agents and bonsai particularly with accidents say, the roots filled the pot too quick and you need to get it through summer/optimum repotting time.

Thanks again!

[shibui]

Really interesting stuff about the first branch eventually becoming the trunk. I’ve never thought of that. Is that common with all bonsai or mainly banksias?

I develop a great many bonsai by chopping back to make the first or second branch the new trunk - trident maples, Japanese maples, pines, some natives. It is a good way to get trunk thickness but still end up with good taper in the trunk.

I'd also be interested in reports on wetting agents in bonsai. I have done very limited testing so far, mainly because I've used alternatives like soaking the pot every few days or week or repeated thorough watering to overcome the problem of being root bound.

[Mickeyjaytee]

Really interesting stuff about the first branch eventually becoming the trunk. I’ve never thought of that. Is that common with all bonsai or mainly banksias?

I develop a great many bonsai by chopping back to make the first or second branch the new trunk - trident maples, Japanese maples, pines, some natives. It is a good way to get trunk thickness but still end up with good taper in the trunk.

I'd also be interested in reports on wetting agents in bonsai. I have done very limited testing so far, mainly because I've used alternatives like soaking the pot every few days or week or repeated thorough watering to overcome the problem of being root bound.

That’s interesting using the first or second branch as the future trunk. I haven’t heard of doing that. No ones mentioned it at all that I remember. I’d assume you cut back to the branch after a few years of development? Thanks for the tip! Really enjoying banksias. They seem a lot more beginner friendly!

[Rory]

I don't use wetting agents. But I am pretty good at repotting and don't let the material get badly pot pound, so I don't normally have a problem with water not soaking into the entire rootball.

What Shibui has said on Banksia is spot on. They are very hardy (most of them) with root removal. I too just cut off chunks of the root, if the material is very old. Having said that, the only banksia I have had many problems with is numerous WA banksias, and the occasional problems from Banksia marginata and Banksia palludosa. Other than that, the more commonly grown species are very hardy. The trick with Banksia is to leave a lot of foliage on them after root removal. It is the one genus that I have never had dieback from after a decent root removal, even after leaving all the foliage on.

And I no longer fertilize any Banksias with anything except slow-release pellets, which don't dump a heap of fertilizer on them after a watering.

I find they are hard to kill from underwatering, but easy to kill from overwatering. But if the rootball is too compact, then yes definitely do a water bath like Shibui says, that is until you get a chance to properly work apart the compact rootball.

Most Banksia will bulge all over the place. its just par for the course with this genus. If you want to reduce the bulging, then yes you can simply pinch off new growth back to 2 shoots. But it looks nice with occasional bulging if you ask me. (personal preference).

[Mickeyjaytee]

Awesome, thanks Rory for the reply and info. So many unique banksia species. I don’t see much of spinulosa ‘birthday candles’ ‘ruby candles’ etc, is there a reason why? I know they’re slow growers (have a few in the garden) but damn, they make a great shrub for an Australian style Japanese garden. Love them!

I’ll keep in mind with the fertiliser. I have been using seamungus pellets so I’ll lay off a bit. I have a few nutans which are slowly developing. Hopefully they aren’t one of the WA species you had trouble with

Thanks again mate

[dansai]

A question for Rory, what do mean by Slow Release pellets? Dynamic Lifter and similar are slow release and come in a pelleted form but can dump their nitrogen pretty quick. Osmocote and similar are considered Controlled Release and release the nutrients more gradually over time. I assume you are referring to the later?

Also it is interesting that you find Banksia fine with under watering. The only time I have lost any Banksia is after they have dried out completely one time. I tend to water pretty heavily as my nursery is exposed to full sun and wind and I have never seen one suffer from overwatering. I have had exactly the same experience with Allocasuarina torulosa. One drying event and they're gone. Although I've had a few reshoot from the base shortly afterwards.