Callistemon as bonsai: summary of AusBonsai posts

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Phil Rabl
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Callistemon as bonsai: summary of AusBonsai posts

Post by Phil Rabl »

The following is my attempt to summarise the information in the 1570 posts on AusBonsai on Callistemon. If you see anything I have missed, or think I have something wrong, please post your comment. And please help to fill in the knowledge gaps.

In the coming weeks the information will be massaged into an article(s) for the Canberra Bonsai Society newsletter.

In case you have not seen them, I have already published summaries of AusBonsai posts on:
Banksia integrifolia (viewtopic.php?f=69&t=27698) and
Eucalypts (viewtopic.php?f=78&t=28106)

Melaleuca and Callistemon: Why are they Different?
First, I think it is necessary to deal with the debate as to whether or not Melaleuca and Callistemon belong to the same genus.
The Australian National Botanical Gardens answers the question What is a Bottlebrush? this way: “Bottlebrushes are members of the genus Callistemon and belong to the family Myrtaceae. They are closely related to paperbark melaleucas, which also have 'bottlebrush' shaped flower spikes. It is difficult to tell to which genus some species belong. Botanists are currently closely studying these plants to determine how they are best classified. There are 40 species currently called Callistemon” and some 300 species called Melaleuca.

The Australian Native Plants Society (Australia) has an article on its website (http://anpsa.org.au/mel-cal.html) that explains the technical difference between the genera. The main difference has to do with the way in which the stamens (the male parts of the flowers) join to the floral tube.
The current (2021) situation is that State/Territory herbaria in the Northern Territory, Queensland, Australian Capital Territory and Tasmania accept the joining the genera, while herbaria in the other States do not at this stage.
Now for the summary of AusBonsai posts.

Early development
Many posts on AusBonsai seek advice on what to do with a newly acquired little Callistemon. What to do depends a lot on the characteristics of the particular tree, and there are multiple posts saying that if your tree is in the early stages of development, you need to think first about what shape would you like for your bonsai.

Remember, as one experienced bonsai artist says, commercial production growers often put the small plant in the bottom of a larger pot then top up with mix which means the roots are all way down in the pot. A well-shaped small tree suddenly ends up as a nicely shaped small tree on a long straight trunk when you re-pot it. Fortunately, callistemons are good at growing new roots so, even if it was potted that way it may have new roots around the trunk just under the surface.

Styles
Quite a few inexperienced (and some experienced) growers ask for advice on styling a newly acquired tree. But, as you would expect, suggestions about styles are diverse.

That said, it’s hard to disagree with the comment in one post: ‘generally, we try to make our bonsai look like the tree would look as a larger, natural tree’.
The following pieces of advice all come from growers experienced with Callistemon. They are drawn from a wide range of discussion threads on AusBonsai.

Keep options open: If you have acquired a tree with some really interesting characteristics, it is a good idea to think carefully and keep your mind and your options open, especially in the early stages of development.

Be guided by the tree: One post commented: ‘I think the natural, humped back style of the plant lends itself to a “turtle back” style but I must research that style more’. It prompted this response: ‘Your research into a range of “styles” such as the turtle back is good background work. Once done, you might like to put them aside and try to get into what this potentially exciting plant has to offer. What is its own character, as opposed to which style-club should I send it to? What is the most important feature(s) of this plant that I want to capture, irrespective of whether they fit a given style? Think about 'line', movement and flow, balance and asymmetry. These will lead you to your best options rather than the dictates of styles. Let the tree take over your creative mind rather than looking at how you can turn it into something is may not be.’

What is the story of the tree?: The following was posted in response to a question about the health of a tree: ‘As for overall shaping of the crown, think about how your tree might have come by the exposed roots. What kind of situation would it be growing in for that to happen? And the two major damage areas on the trunk - they should be part of the story? What is the story that they could tell? That is what you might be looking for. Has that damaging force gone for good, or is it part of the ongoing life of the tree? Is your tree thriving strongly after the damage, or is it subdued though healthy? Answers to these will help decide how big the crown could be and whether or to what extent is should be symmetrical or asymmetrical. Thinking along these kinds of lines might be helpful to you.’

Be brave: When you have decided on the style you need to prune off any branches that don't belong. As an experienced advised: ‘that's the biggest challenge for new growers but don't be frightened. You can't make a mistake because a bonsai can be pretty much any shape and, if you do cut the wrong bit off it will grow back given some time and care’. (See below for much more advice on trimming and back budding with Callistemon.)

Trunk development and taper: ‘I would love some guidance in which way to go with this little tree’ said an inexperienced grower. The reply was: ‘Just having 2 shoots at any point is a good idea. Which one to remove will depend on your aims and stage of development. Generally, branches are thinner than trunks so maybe taking off one of the larger ones would be a better solution leaving a thicker trunk with a thinner branch at that point. Your tree is currently very young and thin. Most people expect bonsai to have solid, thick trunks with good taper. This is generally achieved by allowing lots of growth then pruning back hard. If this is your aim, then leave both thick ones for now as one will probably be removed in a couple of years when the trunk is thick enough. There is not really one path to creating a bonsai. There are many different options that can lead to a good final outcome.’

Keep your tree healthy: A first-time styling of a Callistemon involved bending branches down. ‘To be honest’ was the response, ‘I don't think you're going to do a Callistemon any favours by trying to style it like a pine. I think the biggest problem with forcing the branches down is that it may weaken the tree over time. Styling native Australian trees is a very complex subject, and you'll get lots of different opinions, however I would always look to keeping the plant as healthy as possible.’

Shohin: ‘If you are aiming at Shohin size tree, fast growing techniques can do more harm than good. I think you are on the right track in growing it slowly in smallish pots. My best small trees were all developed that way, but it still takes years of patience. Just don't let it get too root bound. My experience has been that root bound trees die in summer because water cannot penetrate the pot properly.’

Water swept style: There is a lot of discussion on AusBonsai about the uniquely Australian water swept style for Callistemon. Most Callistemon grow as upright spreading trees but along creeks and rivers they can be water swept. This style should not be confused with windswept.
As the owner of a beautiful water swept Callistemon said: ‘Water swept styling is suggested by the trees that grow in the rivers around this area. The ones that germinate on the rocks in the riverbed are subjected to annual flooding and all have similar characteristics - elongated branches pointing downstream, roots flowing over the rocks seeking footholds and nutrients from the cracks, damage to upstream side of the trunks from being bashed by debris in the floods so that is what I've tried to incorporate into the bonsai. I like to think this is a unique Australian style.’
If you create a water swept design, you may need to do a really hard trim and a lot of thinning out.

Flowering
Flowering is a priority
If flowering is a priority, you need to manage your pruning and light trimming regimes.

One post describes the pruning regime for the Callistemon viminalis "Captain Cook" at the NBPCA: ‘My aim here with our callistemons is to prune very hard after flowering. Then feed well and allow elongation and strength. Usually trim these elongations back to a nice shape by the end of January, then pinch prune till the end of February. I feed with bloom booster (or equivalent) during Summer and Autumn. The flowers set on growth during this time, not on subsequent Spring growth. I generally trim the extended Spring growth back after it is obvious where the flowers have set. This allows for an uninterrupted display of flowers. This tree flowers in November or December, so it is cut back by New Year.’ (NOTE: the timings in this advice reflect the Canberra climate.)

One grower with 20 years of experience with callistemons says he has always had flowers. ‘The important thing to remember,’ he says, ‘is that they flower on new growth. So, you can prune them hard after flowering and they will power away again. If you keep pruning for shape you will lose the flower buds. So, cut back hard after the flowering season (normally in spring and early summer) even if it has not flowered. If your tree has never flowered, you will need to do a little research. Let it grow for several months then, cut to shape but do not prune again until after flowering. They are very apical dominant, so you need to make sure the apex is still tapering. You can pinch tips for ramification, but that is it if you want flowers next season.’
Another experienced grower makes the same point: ‘Callistemon flower at the tips of last season's shoots so, in order to have flowers I need to allow the shoots to grow after February. That means the tree gets bit shaggy. After flowering the tree can be cut back really hard to start the cycle again.’

Flowering is not a priority
If flowering is not a priority, you can trim Melaleuca and Callistemon pretty much at any time. ‘Some species do not flower readily, and other have flowers that you might call ‘less spectacular’ than others. And many species have very attractive foliage that you might like to highlight.’

Trimming and pruning
NOTE: You should read the advice on flowering in conjunction with the advice on trimming.

There is general agreement in AusBonsai posts that you can remove excess branching on Callistemon at any time.

In the colder climates, however, there is a consensus that heavy pruning should be avoided in the run up to winter. There is little or no precise advice in posts on Callistemon as to when you should stop heavy pruning, but in other forums there is a general view that pruning, carving and root pruning should not be done unless you are sure there is at least 6 weeks of warm weather remaining before the growing season effectively stops.

As one very experienced and respected grower said: ‘At the beginning of this year I decided to take the lower branch off and carve the upper trunk to induce some taper. At the same time, I did a heavy trim to bring it back to a better shape. This trim resulted in the tree struggling through winter. I will re-evaluate what time of year I do this next time.’
Aside from the time of the year, you should make sure your Callistemon is in good health before doing a heavy prune.

Back budding and trunk-chopping
There are numerous questions about whether it is safe to prune callistemons heavily or to trunk-chop them. The universal answer is ‘yes’, but don’t expect every species to react the same.

One post says: ‘Fortunately C. sieberii bud really well; so well that it frequently produces buds on really old trunks without being pruned. Rub off unwanted buds as they appear.’

And another: ‘Almost all of the ones I have chopped have produced lots of new shoots from the old wood. Sometimes it can take a few months, occasionally 6 months or more. I have collected one which had small, narrow leaves and a really large lignotuber. It has produced lots of shoots but only from the lignotuber base.’

Healing after a chop
Questions from those with limited experience with Callistemon include:
• What is the best post chop after-care?
• how long will this take to heal up and look nice?

In relation to after-care, a very experienced grower said: ‘The answer is pretty simple: treat it as you would all trees that have just been chopped or re-potted. Not too much water, not too much sun, and not too much wind. Do not start fertilising until you see new growth.’

Another post from a different experienced grower says: ‘Keep them moist but not wet, and apply Seasol regularly, (2-3 times a week) until you see new growth. Once they have established a good crop of fine roots you can cut them back hard, but not after new collection or acquiring. Keep under cover of other trees or shade cloth so that they are not overly exposed.’

In relation to how long it takes to heal, one post asked: ‘How long is a piece of string? The time for this to heal will depend on so much - how well you grow it, whether you allow free growth or restrict it (pot/ground), where you live, etc, etc. My callistemons grow quite quickly and heal well. I found I had to keep widening the shari on my waterswept Callistemon because it kept threatening to heal over.’

The post went on to recommend feeding and watering to promote growth, which will speed the healing process. It also noted that growth does not necessarily mean creating one long shoot. ‘Thickening depends on number of leaves (or more importantly leaf area) not height of the shoot so even regularly pruned leaders that produce plenty of side shoots can cause effective thickening and healing. With rough bark varieties, scars should be unnoticeable soon after it heals. Also note that I have done trials and I am convinced that sealed cuts heal over far quicker than those left bare.’

NOTE: You will see from these posts, all from experienced bonsai artists, that the advice on whether or not to feed a tree following a chop is inconsistent. It is often said that Seasol is not a fertiliser, but a plant tonic. This is a confusing distinction to make. It is true that Seasol does not come with a declared NPK ratio, but it certainly contains nutrients for the plant. The Seasol website has excellent information on fertilisers, including these statements:
  • ‘A fertiliser is any substance, either natural or chemical-based, that is applied to soil or plants to increase yield or performance and comprised of nutrients essential for plant growth.’
  • Organic fertilisers and plant tonics are those fertilisers and plant tonics that are made from a substance that was once living such as animal manures, seaweed, kelp such as Seasol, spent cereal crop waste or peat. These formulations are often fortified with naturally occurring rock minerals or nutrients.
Fertilising
Discussion threads on AusBonsai about fertilising Callistemon cover the full range of issues and views typical of discussions on fertilising.
First, what fertiliser to use on natives: one post said: ‘It is absolute rubbish that natives don't like fertiliser. True there are some that resent phosphorus (P), but the vast majority are fine. I use the same fertiliser on Callistemon as on all the exotics. The species to be careful of include Banksia, Hakea, Protea (non-native) and Grevillea.’

‘I use Powerfeed even on banksias. I use thrive and fish fertilisers and Chook poo pellets (Dynamic Lifter is only one brand) on all the other natives. I also use standard Osmocote in the mix for all except Banksia and last year and this I have trialled some seedling banksias in standard Osmocote mix and have not had any adverse reactions. In summary, Callistemon will not care what fertiliser you use. Just apply according to the instructions on the container.’

NOTE: understanding phosphorus sensitivity in natives requires an understanding of Proteoid roots.

As Gardening Australia comments: We've often been told that native plants won't tolerate even moderate phosphorus levels in fertilisers and soils. This view, although incorrect, is deeply entrenched. So much so that commercial interests actively market fertilisers, low in phosphorus, specifically for Australian natives.

While the origins of the erroneous advice are unclear, they surely stem from the fact that (some) Australian native plants thrive in nutrient-poor soils AND sometimes grow cluster roots known as proteoid roots.

The issue is that proteoid roots are known to increase the uptake of phosphorus, and other nutrients, and that applying a phosphate-rich fertiliser could cause the tree to take up phosphorus at a toxic level.

As first described in 1894, proteoid roots are extensively branched roots covered with long, densely grouped absorption hairs. Helen Purnell, the Australian scientist who coined the term ‘proteoid root’ in 1960, described them as a root with dense clusters of rootlets of limited growth.

But not all Australian natives grow proteoid roots; and bonsai enthusiasts routinely and safely apply fertilisers containing phosphorus to their natives, including those that can grow proteoid roots. So, where does the truth lie? The full picture with regard to proteoid roots is complex and incompletely understood but there is lots of information that can help the bonsai enthusiast with trying to understand how best to manage (or avoid) proteoid roots.
One post included a very useful link to a P sensitivity study on the Australian Native Plants Society (Australia) (ANPSA) website: http://anpsa.org.au/APOL8/dec97-4.html.

People tend to have their own fertilising regimes:
One post says: ‘I use Miracle Gro for azaleas and camellias once a month and use Phostrogen once a month. Alternating fortnightly. This is my standard fertilising regime. All my plants get this except the miracle Gro is not used on my exotics.’

Another says: ‘Leaving unpruned tips is only one factor affecting Callistemon flowers. I've found that they definitely respond to high K fertiliser just like other flowering exotics so I use Thrive Fowers and Fruit from about mid-summer. Any fertiliser aimed at flowering or fruiting plants can be used - tomato, azalea, rose, citrus, etc should all be suitable.’

Wiring
You can wire Callistemon at any time of the year. Don’t wire branches when they are very young. As one post notes: ‘Callistemon can be wired and bent when the branches have lignified.’ Remember too, that Callistemon branches tend to become brittle as they mature. So, don’t leave wiring too late either.

Watering
There is a general consensus that Callistemon need to be well watered but that either over- or under-watering can set the tree back. And it can be difficult to tell what the tree’s symptoms are telling you.

As one post says: ‘Hmmm. Your callistemons either have too much water (brown soft leaves), or too little water (brown crunchy leaves), or your issue is not watering at all, but pest or disease related.’

Another says: ‘It sounds like you are either under watering, or over watering. The first rule to grasp, is that when someone tells you a species is thirsty, or requires a lot of water, this may be true, but you have to put this into perspective, as this does not mean the tree wants water continuously, it just means you have to monitor the levels more often for when it does need a water. Under-watering, can often occur in the sense that the root ball is so compact, that water is only barely able to penetrate the edges of the root ball even after you have given the tree a long watering, and thus the main heart of the roots is not getting enough water. You would be able to see this during a re-pot. However, if you are leaving the roots to soak for an extended period, then by natural absorption, the water will fill all the nooks. Over-watering is the other most obvious candidate. The symptoms of over watering are similar to under watering, in the sense that the roots cannot breathe and thus cannot transport nutrients or water to the tree. Basically, as the roots rot, the leaves start to wilt and discolour. You can usually tell if it is under-watered because the leaves will wilt and dry very rapidly, whereas an over-watered tree takes a longer time to die.’

Drying out will not necessarily be fatal for a Callistemon. A very experience bonsai artist says: ‘Never throw a Callistemon or Melaleuca away for at least 2 years. … The upright tree in that post is called Houdini because it died four times, or so some people thought. Well, here it is. If you search AusBonsai for Houdini you will see progression of it.’

Another post warns us not to be too literal about the advice that Callistemon need a lot of water, especially for growers in humid zones or colder climates such as in Europe: ‘When books or sites tell you that Callistemon need plenty of water, they are referring to Australian conditions that are mostly hot and dry. Some of the other States have hot humid conditions. When you are keeping them indoors they will not need as much water. Like all plants that are grown indoors it is a foreign environment. So, you have to make allowances. The soil needs to be moist, but not wet.’

Re-potting
When to re-pot
There is a general consensus that it is best to re-pot Callistemon in the warmer months, although some say they are able to survive a winter root prune.
As one experienced grower says: ‘They can survive root pruning in winter but lots of other natives will not. Aussie natives seem to prefer to have roots pruned when the weather is warmer - late spring through summer seems to suit most and they will start growing back almost straight away.’

The same grower also says: ‘I re-potted some callistemons and melaleucas last week (late January). They do not seem to have any problem with root work when it is hot but some banksias I root pruned in March a few years ago as a trial just sat and sulked all winter. It was just a bit too cool for them to get going again at that time of year. I re-pot any natives from late spring through to late summer and most survive and grow really well after, even if the weather is hot.’

There are differing views on the advisability of re-potting in late summer and early autumn. One experienced grower says: ‘The question should really be not whether you can do it now (early February) but whether it is advisable. Generally, the answer must be no. All my natives are in the absolute full growth phase at this very moment. I want them to put on the maximum amount of wood they possibly can. Now, what will a root pruning do to them. Answer: reduce growth. Simple. So, unless it is necessary for some valid reason, such as an emergency like a broken pot, or you don't have the time do it at the correct (preferable) period, then I can only repeat that you shouldn't.’

Another says: ‘I am not as strict as some of the members here, I simply start re-potting when I have the time, about December but I have no qualms doing Casuarina and Callistemon in October - November. From previous experience I am strict with eucalypts, and I only try to re-pot them in summer. But with Callistemon I don't see any problem. I have re-potted two just recently (January).’

Another says: ‘I find anytime through late spring to February, no later is fine. Heavy root prune, to eliminate twisting roots, trim tree hard before you do it, same day of course, and you will be fine. Use very coarse open mix, to let the oxygen in to the root system. Style, wire, of course, before you re-pot. Just finished all of mine this week (early February). Will reshoot within 10 to 14 days. Give them lots of sun, and air movement, but not on temps over 30 degrees. Never do any natives in winter. The warmer the climate you live in, the more choices for re-potting.’

A grower from Sydney says: ‘I repot mine in late spring. You can do them almost all year round here as they never really stop growing.’
Another post comments that ‘when re potting is discussed, questions that always pop up are what is the best time? The inevitable answer is at bud burst. The next question is what is bud burst?’

The warmer months are the active growing season for Callistemon. While the timing varies with local climates, there is a broad consensus that re-potting when the trees are actively growing is safest.

One grower asks (in response to the post on bud burst): ‘does this mean that if I trimmed back a Callistemon and it’s throwing out buds now I can re-pot now even though it’s quite late with the hot weather on our door step?’ The answer was ‘yes’.

Heat
There are words of caution about re-potting in very hot weather. As one post says: ‘We are heading into a week of temperatures in the late 30s to early 40s, so any thoughts of re-potting is going to have to wait. I did a Banksia in late November, next day it was 48 degrees, so it sulked for a while. Some shoots were singed. Lost two melaleucas. So, saying when and what time is reliant on weather in your area.’

How hard to root prune
There is plenty of advice on AusBonsai that if re-potting is done in the warmer months, Callistemon roots can be cut back quite hard.

One post says: ‘I usually cut mine fairly hard - around 70% reduction. Have gone as far as 90% with some trees collected from gardens. Most survive but have lost one 'Little John' which was left with no feeder roots at all. I don't use Seasol and the trees go straight onto the grow benches in almost full sun after re-potting. Others report success after soaking in Seasol and some shade after repotting. Just shows that a range of methods will work. Leave it to you to choose which way feels right for you. Summer is the best time to re-pot Callistemon.’

There is no advice on how hard to root prune if you are re-potting in cooler months. There are, however, suggestions that autumn root pruning should be done earlier rather than later so that the tree can recover before winter dormancy sets in.

Aftercare
A post from an experienced grower says after care should include: ‘Not too much sun not too much wind and not too much water in the soil but plenty on the foliage as in misting. This may not be practical when you are working or studying! So some shade till it shows signs all is well. I also use Seasol or one of the other Auxin providers!’

Nebari
One post asked for advice on what to do if your tree has a tangle of surface roots. The answer from a grower with nursery experience was that tangled surface roots is not uncommon with nursery stock. He said ‘you should dig away the soil around the trunk and clean up the roots. You can remove the tangled knot of roots at the base of the trunk with a pair of knob cutters. This does not need to be done in one session. If you are worried that removing the tangle will kill too many feeder roots, you can spread the task over two (or more) growing seasons.’

Temperature
A question from an inexperienced grower in Germany prompted an interesting discussion on the temperature range suitable for Callistemon.

The NBPCA noted that ‘Callistemon will grow in many different environments around Australia; Perth western Australia winters are very mild whereas in Canberra it is quite a lot colder. Australian native plants in general will continue to grow all year if they have warmth, light, water and food.’ But it would be impossible for a Callistemon to survive a temperature as low as minus 15 degrees C.

The NBPCA reported that one Callistemon at the collection sustained some light tip damage when the overnight temperature dropped to minus 9 degrees C.

Propagation
Layering
One post asked if air layering an old Callistemon would likely be successful. The answer was “yes”.

‘I have done quite a few and usually all are successful and pretty quick too. I did mine in winter and they only took 2 months or so. Used the plastic wrap Method.’

‘Most layers can survive with relatively few roots and Callistemon is no exception.’

Cuttings
There is a general view that Callistemon strike very well from branch cuttings.

Discussions on how best to take a cutting include recommendations to use honey to help them strike, which the poster says helps him get a strike rate of 90 per cent.

When striking a cutting, the same poster says he uses ‘a coarse mix of 50% crushed gravel approximately 2mm with 50% coco peat, as in choir peat blocks from any of the big hardware or garden centres. The peat block is soaked in 4 and a half litres of water then drained off.’

Collecting
It is quite possible to collect Callistemon, although mixed results are reported in AusBonsai posts.
Multiple posts indicate that a successful outcome is most likely if you prepare the tree before digging it out. One post recommends:
• applying a quick release fertiliser with a high P:K ratio a week or so before trimming the plant down so that it has a good store of energy to draw on.
• clearing the grass away from the trunk and top dressing it with mulch.
• leaving a lot of leaves but removing tip growth to stimulate back budding.
• keeping Callistemon moist after digging out.

Another says ‘if you are thinking of digging up a Callistemon (especially if it is in your own garden) you have two options:
• Cut it off (low down if it has a straight trunk) and leave it to shoot before digging.
• Dig and prune in one go.’

And remember, they sometimes have substantial roots!

There are numerous other informative stories:

One says: ‘Callistemon always surprise me with how tough they are. I dug one up a few months ago with practically no root, at a bad time, and it wasn't the healthiest. It dropped all its foliage and I thought it was dead for sure... Too lazy to throw it out and sure enough, it's pushing new buds all over now.’
And another: ‘I pot all my collected trees into my own mix, and do not differentiate between newly collected trees, or “Bonsai", every tree deserves the best chance they can get, and a good soil / substrate will help. Any of the quality commercial mixes I assume will be OK, but you never know until you open the bag.’

And another: ‘Natives can be collected at any time, just like most trees spring is preferred. Just take as much root as you can handle and pot up. Aftercare is the key. Keep well-watered and use Seasol for the next 2 -3 months, or until you see positive continual signs of growth.’
And another: ‘Don't worry too much about mix for grow boxes. The larger the container the less critical it is to have good mix. I'd just use a premium potting mix with added fertiliser.’

Defoliation
There are inconsistent views on whether or not you should defoliate a Callistemon.

Deadwood
As one post says: ‘many Australian trees feature dead parts because of the harsh climate here. Drought, floods and fires all take their toll on trees in the landscape so I think it is natural to include dead wood in our Australian bonsai.’

Pests and Diseases
AusBonsai posts do not provide a comprehensive list of pests and diseases. Also, it is likely that there will be major differences from location to location and between species.

Webbing Caterpiller
One post asked: ‘What is this critter building nests in my bottlebrush?’ The comprehensive answer was: ‘That will probably be Tea Tree Webbing Caterpillar - Orthaga thyrsalis. The grubs will be hiding in the webs if they are still there but often, by the time you notice the webs they have already grown up and made cocoons. Some of them drop onto the ground when they feel threatened so, again, you don't see them when you search. Apart from squashing them, anything that will kill caterpillars will treat these guys. B.T. - sold as 'dipel' is a very safe caterpillar killer. It is actually a fungus that can only attack caterpillars so will not hurt you, dogs, ladybirds, etc. Pyrethrum sprays will also kill them but you do need to get it onto them which is a bit hard because they are hiding so well. Systemics are a bit more harmful but are effective because anything that eats any part of a sprayed tree will die.’
One post kindly provided a link to an article on this pest on the ANPSA website. http://anpsa.org.au/APOL2009/jul09-1.html

Another post recommended a non-chemical control: ‘Yes, webbing caterpillars are always an issue. Just like you did, watch out for them and pull off with your fingers; works well and without poisons.’

Callistemon Psyllid
A post asked: ‘What are these weird lumps on the leaves of my Callistemon?’ The answer was: ‘They look like Callistemon Psyllids.’ Psyllids (and their nymphs – lerps) are sap-suckers, causing damage to the newer growth of susceptible species between early spring and mid-autumn. (source: Searles gardening) For an organic solution, treat with white oil otherwise try Searles Conguard. As one person said: ‘If you want to avoid using Confidor, which is way too toxic for me, I use Eco-oil mixed with neem oil. Safe to use and very effective.’

Fungus
A post said: ‘My Callistemon Little John got hit by a fungus.’ But one response questioned the diagnosis: ‘Got a question about your fungal attack... did it only happen in the areas that you cut back? All of my Little John varieties respond to every other pruning or tip pinching by producing some die back at the tips that looks like a fungal infection. Apparently this is normal for the variant and mine always power back. If this is the case, it has been recommended to me to remove the dead tips as they can harbour pests.’

Leaf damage
‘Hi everyone’ said a poster, ‘what’s going on with my Callistemon? The tips of the leaves are going a speckled dark colour.’ There was no clear answer provided for this question. One reply said: ‘the first thing is to ask yourself is, pest? or disease? And I don't know, sorry. But, I have a few Callistemon in large pots, not bonsai, and had the same problem last year. I gave it a root prune and pruned the outer branches to match the root removal and cut all the remaining effected leaves off, leaving about 2-4 mm, they died and were replaced quickly with the next set of leaves, they came back free of the problem.’

And another: ‘I've seen this with some Callistemon, and I'm not sure what it is either. I'm not even are if it's a normal thing or a problem.’

And another: ‘I have similar observations. I experience a very similar colour change to your photo as older leaves ultimately die-off and are (hopefully!) replaced by new growth. I tend to notice it most after aggressive root work when I assume that I've left more leaves on than the reduced system can support and the tree is correcting the balance.’

Mildew
Another poster was worried about the fine white growth throughout the soil. ‘Relax’, was the answer, ‘it's mildew in my opinion, it will be fine, just spray 30:1 lime sulfur.’

Another post (on a different thread) said: ‘A great alternative for controlling powdery mildew is to spray with a 1:10 mixture of milk:water. Skim milk will do just as well as full cream. This treatment seems to have been discovered in Brazil. I've used it on zucchini to great effect, as well as on susceptible bonsai. The Australian National Botanical Gardens uses it as its preferred treatment. It appears that it is some of the proteins in milk that kill off the mildew. For those not wanting stronger 'chemicals' it is ideal.’

Afterword
In due course, I intend to do a summary of AusBonsai posts on Melaleuca. It will be interesting to see how closely the advice mirrors the advice for Callistemon.
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Re: Callistemon as bonsai: summary of AusBonsai posts

Post by boom64 »

Fantastic work Phil ,printed and filled away for further use. Cheers John.
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Re: Callistemon as bonsai: summary of AusBonsai posts

Post by melbrackstone »

Thanks for bringing this to our attention, I missed it when you first posted.
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Re: Callistemon as bonsai: summary of AusBonsai posts

Post by Redsonic »

Yes, thanks for the information. I too missed it for some reason
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Re: Callistemon as bonsai: summary of AusBonsai posts

Post by stroven2022 »

Excellent read!!
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Re: Callistemon as bonsai: summary of AusBonsai posts

Post by Patmet »

As requested by Phil earlier this year, I would just like to add the Callistemon Glaucus/Albany Bottlebrush here. For anyone wanting to have a go with a different Bottlebrush I can highly recommend it from my experience over some years.

Most of the same general Callistemon advice applies, but if you're interested in specifics to this species I have a thread running for it here - viewtopic.php?f=55&t=30002

I don't know if it's easy to find in nurseries in the eastern states, but I believe it would do quite well over there.

Cheers, Patrick
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