I have always been unclear about whether or not one can use conventional fertilisers on rainforest trees and shrubs. Are they phosphorus-sensitive like so many natives - or not?
Not as phosphorus sensitive as most Oz natives, but they really do like lots of slowly-rotting organic mulch. Leaf based in particular, but can cope with grass cuttings, mushroom compost, etc. I give mine blood and bone, with an occasional dose of soluble fertiliser. That seems to keep them very happy,
Conventional wisdom has it that most rainforest plants will handle 'standard' fertilisers such as Osmocote, but I had an experience with an advanced Penda (Xanthostemon Chrysanthus) recently which led me to wonder if I may have indavertently poisoned it. Lost a stack of leaves and looked quite unhappy for about a week - since then, I've been careful to restrict fertliser to the palms in the same bed. It may have been pure coincidence, but I'm not prepared to lose a $30 plant simply because reality differed from my expectations.
Happily, the Penda has regained much of its former glory, and I'm eagerly awaiting new growth following our recent rain here in Rocky.
My final observation concerns the term 'rainforest plant' : if we include things like tropical Grevilleas in that group, then we definitely have a problem with high phosphorus fertilisers.
Well if grevillea robusta is anything to go by, tropical grevilleas are quite happy to get plenty of fosforus. I find that dosages comparable to those for potted colour are quite fine.
While we're on this subject, what's the thinking on fertiliser for lemon myrtles (Backhousia citriodora)?
I guess they're rated a rainforest item.
Would Osmocote be preferable or would I get away with some blood and bone?
I have a B myrtifolia in my orchid shadehouse that gets stacks of (half strength) orchid fertiliser with a fair bit of P in it. It doesn't seem to have suffered, but obviously it is not a very vigorous scientific experiment!
Anyone wanting to fertilise their Natives would be best staying with a low Phosphorus based slow release fertiliser along the lines of an 'Osmocote Plus' for native gardens. This has an analysis for N.P.K of 17.0 (N) 1.6 (P) 8.7 (K)
I also use a fertiliser which contains a slow release plus IBDU, but this may not be suitable for rainforest plants as living in s/e Victoria rules me out for growing them.
CSIRO did a study some years back regarding P in fertilizers for natives and they found that only a small handful of W.A. species were significantly affected by strong doses of P. I think the 'native fertilizer' story is almost myth. If you grow special SW-WA or tricky proteacea then you should worry about P. For the rest of us, a normal fertilizer should be fine.
I personally use a normal mix fertilizer on everything without trouble (including eremophilas, stylidiums, rock wattle, verticordia and tricky alpine species). And natives grow a lot better given more P. Perhaps the reality is that natives can deal with low P better, but I think they do indeed enjoy a good feed.
I guess it all boils down to what works with your plants and if they perform with what you use.
What ever works for you and you get good results, stick to it. A low phosphorus fertiliser is my choice, because it works for me.
"What ever works for you and you get good results, stick to it."
Unfortunately I hear people say that all the time. In reality if you aren't trying new things regularly your gardening never reaches its fullest potential. As a random example, Don Burke didn't trust the 'whatever works' theory, and instead bought 300 tonnes of crushed rock to grow his grevilleas and was the ridicule of the garden industry. It paid off. But I bet he tried lots of things before he settled on that approach.
In the orchid society I have somewhat of a reputation for trying out silly ideas. Many fail, but I have made some progress on the propagation of orchids. Mostly because I like to try things out myself.
(One problem with your statement is the fact that you can't qualify 'good results'. Good compared to what?)
Point taken, but - I grow Correas and actually use a Two in One fertiliser, containing low phos Osmocote and IBDU. This is applied as soon as I know roots are present on the cuttings, which is something that works. I don't have to compare it to anything because the results speak for themselves, but I don't advertise it because it may not work for you.
As for Don Burke, he had more experience with gardening because he was a qualified horticulturist, more than Mr or Mrs average gardener. Silly ideas might work in the Orchid society, but you've got to take a lot of things into consideration in the home garden (eg soil type) when applying fertiliser to avoid killing off your plants while trying to be different.
Low Phosphorus fertilisers are recommended for Natives because they have been tried by experts and known to work. I'd rather kill my plants with kindness than go out experimenting with anything just to get a reputation for being different.
At first I found your post rather odd, but I think the difference is that you believe information comes from authority, whereas I believe in science. Science is about disproving hypotheses, and where I can't get reliable information to justify an opinion I generally try to derive the idea from first principles, failing that, I do an experiment. It is often surprising what does and doesn't work.
If you get a chance to read Burke's Indigenous, I strongly recommend it. My reading was that he found the horticultural training somewhat unhelpful. He did his crushed rock experiment against the recommendation of 'experts' and got ridiculed in public for it. This is not how you are presenting him. You also seem to believe I am motivated to try things to "get a reputation for being different", in fact I am motivated by new knowledge rather than some superficial comparison to others (something that most people either can't comprehend, or find terrifying for some reason).
All the great gardeners I know experiment all the time. This new knowledge trickles down eventually to 'experts', but considering the number of so-called experts I've met who talk complete rubbish I'm dubious of anything they tell me. (For example, the grey water systems being promoted by gardening australia are completely ridiculous, spending thousands of dollars for tanks and pumps and filters. oasisdesign.net on the other hand have robust and effective greywater systems that cost tens of dollars and require far less maintenance. (Josh Byrne admitted to me that this was true, but due to retarded legislation in several states that is the best they can promote)
Low phosphorus fert. may 'work', just like only watering when the plant starts to wilt, but higher levels of application may improve growth dramatically. Stating that all natives should be given low phosphorus means that many gardeners will either be put off natives (due to fears about interaction with other species' needs) or will miss out on years of excellent flowering.
Here is a link to some real research done by SGAP - Phosphorus Needs of Some Australian Plants. Note that, for example, Grevillea robusta will use more phosphorus than was given in their trial. I predict that correas and most commonly cultivated natives will be in the first 3 categories.
Nathan, regarding Don Burke's crushed sandstone idea for growing native Proteaceae plants.
The idea he suggested as being revolutionary, was and still is in fact old news and has been used in lanscaping Proteaceae for ages. As far as I am aware he was not ridiculed by the garden industry. Some may have made a few sarcastic remarks but I personally am not aware of them. They may possibly have made the remark that it is old hat.
Crushed sandstone is frequently used to create native gardens as it solves the problem of having to deal with difficult soils.
Nathan, in two posts now you mention Don Burke and his sandstone rubble garden, so let me say that having been an avid Burke's Backyard viewer, I too remember the rubble garden Don put in.
I have since located the write up on this garden on the net and low and behold what do you think Don used as fertiliser?
Have a read -
"Native plants are fantastic in the garden because they look wonderful, they attract native birds, they grow quickly and they keep Australia looking like Australia. The native plants shown in our segment included Grevilleas, Banksias, grafted Darwinias and lots of wattles, mostly dwarf varieties. The garden will mature quickly in about two years, whereas an exotic garden would take 10 years or more. The garden was fertilised with Debco Green Jacket Formula 5, a low-phosphorus slow release fertiliser which is only available in 20kg bags. Few nurseries stock it but most could order it in for you. This method of gardening duplicates the wild conditions for most of these plants and some of the best native gardens are those grown in rubble".
So there you go - Don Burke did in fact build a rubble garden, BUT he also fertilised it with LOW Phosphous fertiliser.
Ok, I'm wrong. I'm clearly not wanted here. Have a good life.
I wonder if your Penda might have suffered from accelerated breakdown of the Osmocote in the hot weather leading to increase dumping of the nutrient? I believe these formulations don't last as long in the higher temps, don't have the threshold figures handy though.
I sometimes wonder if r/f species with the usually abundant birdlife that goes with them do have higher tolerance/ requirement because of the P in the droppings. I am sure I under fertilise r/f tubestock, see a good response to a moderate feed of ordinary Osmocote eg for Meliocope rubra.
A while back a poster was wondering about a specific plant and concerned that the P in blood and bone would be too high. It took a long time for the light to go on, I think that this P is essentially slow release.
Thanks everyone, you've been most helpful. And thanks, Nathanhurst, for the pointer to the CSIRO study. That was an eye-opener. Wish it had included Telopea Vs Alloxylon species.
Further to that, I have just searched the ASGAP site and found a piece on Telopea which quoted two pieces of research which cancelled each other out - one said Telopea laps up phosphorus and the other echoed conventional wisdom.
Are you just feigning hurt, I hope so?
Your contribution here, over time has been fairly substantial, so I would hang in.
We get some pretty diverse opinions, even odd ones here, but hell, we share one thing, we all love native gardening in our own ways.
I believe the query was about rainforest trees and shrubs. Talking about grevilleas, banksias, correas, etc is a bit off the topic. In my experience I have never had any problem with rainforest grevilleas, banksias, etc. when feeding them conventional fertilisers, though I do tend to use fertilisers conservatively as I believe most native gardens don't need it once plants are established if the soil has been appropriately prepared in the first place. Don Burke's grevillea experiment showed that they do well in sandy rocky soil with a low phosphorus fertiliser. They tell us nothing about what quite different plants do in quite different soils.
Rainforest plants get their natural nutritional needs from lots of mulch so to save the worry about what fertiliser to use, just use lots of mulch and well-rotted compost. The plants will grow better, need less water, and the soil will improve. Fertilisers, in the long run, do more harm than good to the soil.
Re low phosphorous argument: what works for one may not work for another, experience is the only way to find out for sure. By all means stick to the proven ways to be safe but the recommendations are just a general one for a large variety of plants (to cover the rear-ends - to put it nicely - of the people recommending them ), some of those plants may actually prefer more or less.
I am also a big fan of Don's Grevillea garden, and his ideas in general, but I believe that it highlights the need for experimentation, as Nathan suggests. The problem is that the majority of us are so frightened of losing even a single plant, much less an entire bed of grevillea, due to fertiliser 'poisoning'. I am confident that my Grevillea bed has good drainage - they have survived several tropical storms - but I dont want to introduce anything beyond blood-and-bone into their root systems. I do look forward to hearing from others in the CQ area who have the courage to experiment with fertiliser around Proteaceae.
If we exclude that family from the discussion, I believe that the other rainforest species should be fine with mild doses of a quality slow-release fertiliser : chances are that those of us who have native trees and shrubs interspersed with gross feeders such as palms are already subjecting them to a significant amount of fertiliser (Organic Xtra, in my case). Ultimately, I want to recreate the natural decomposition that they would enjoy in the rainforest, but thats still a few years off, so its a case of 'a little often'. As I have natives which dont receive any fertiliser at all, I'll post again in 12 months with comparisons.
I'm with roysta.
Please Nathan come back. Your contributions are important to this forum. And I especially like your emotive additions.
Come back please!
I must also say this is an informative and interesting post.
Well, I found it interesting off topic and on. Probably unlike most of you, I grow exotics and natives cheek by jowl and have always assumed I shouldn't fertlize the exotics except with compost and a bit of cow manure, for fear of harming the natives. My query really related to some lilly pillies I want to speed up to hide the neighbours - I was still assuming that rainforest lovelies like my Dorigo Waratahs should be kept as far as possible from conventional fertilisers. However the discussion and links have led me to query received wisdom. (Still not going to take a risk with any of my waratahs, though.)
Something to consider and experiment with more:
I have used some straight ammonium sulphate fertiliser on rainforest Proteaceae, for fear of poisoning them with P otherwise. My reasoning was that they were mulched, and with all that carbon source there, the level of N might have been reduced too much. I only used a very little, in case they were burnt, and only when they were small. It does not seem to have harmed them. A north Qld Tree Waratah seemed to be slow taking off and the fertiliser may have helped it grow better.
One of the common admonitions I regularly see against the use of too much additional nutrient (incl water) is that you can inadvertently end up with 'weak' plants that cant stand on their own when they do have to face a little adversity. Whilst I think there is some truth to that in certain environments (the proverbial 'hothouse flowers'), my personal belief is that the Australian climate throws so much at our plants that any advantage we can give them in the early years has to be a good thing. Realistically, we should be aiming to improve the *soil*, rather than simply feeding plants, and that has to be a good thing. I know that many gardeners swear by controlled-release inorganic fertlisers, but I'm keener on building up the layers of organic mulch and compost over my plants.
"One of the common admonitions I regularly see against the use of too much additional nutrient (incl water) is that you can inadvertently end up with 'weak' plants..."
There is something in that. An interesting fact I learnt is that councils, in trying to meet their environmental duties and avoid discharging sewage effluent to waterways, have been heading towards land disposal. Sewage effluent still has some nutrients, and is suitable for irrigation, or can easily be made suitable with adequate treatment (it will always also be disinfected), unless it has high salinity.
Councils have looked into using the effluent to grow various crops. One of those was timber trees. Apparently though, at least in one study I have heard of, it made the trees grow too fast. The resulting timber was too soft/weak and unsuitable for sale as structural timber.
They have also tried other crops, and in most cases without success, because the crop was unsuitable for various reasons. But there has been some success in NE NSW with some crops that produce fibre for bagging etc.
So I suppose that extra nutrients would be OK for some, if not all plants, but you would just have to be careful not to overdo it.
Experimentation is fine if it is based on understanding the peculiar aspects of what ever plant we are dealing with.
When it comes to Australian native Proteaceae plants there are unique considerations that need to be taken into account. Once we have an understanding of these characteristics then by all means we can take advantage of them. Experimenting blindly is not nearly as constructive.
Australian Proteaceae plants are sensitive to Phosphorous to varying degrees. BUT it all makes sense if we are aware of what their original environment was. Proteaceae from the skeletal sandstone soils that have always been very low in nutrients, especially phosphorous, have over thousands of years, developed special adaptions known as proteiod roots. They are noticeably different. (I shall spare you further details about Proteiod roots, but a Google might give you more.) Plants developed these in order to maximise the surface root area so they can absorb the scarce nutrients that may be present in these sandstone derived soils.
However in the more nutrient rich rainforest zones it is quite possible that Proteaceae are more tolerant of nutrients and maybe even Phosphorous. I always err on the side of avoiding common fertilisers with high rates of phosphorous. Even chook poo can cause problems, although I do give my rainforest plants a dose of Dynamic Lifter once a year.
For example, I find Banksia ericifolia to be very sensitive while some Grevilleas are a bit more tolerant.
As for your last remark Nathan I assume it is a joke. Anyone being wrong, should not inferr anyone is not wanted.
Goldhills' point about mulch is important - I should have mentioned it. But I stand by my point that I have never seen or read of phosphorus toxicity from normal use of fertilisers ( "even chook poo" contains huge amounts of phosphorus) in rainforest plants. I just felt I could add my experience to the discussion. Those who quote "all the experts say..." should be aware that most "experts" who write gardening books get most of their "facts" from other gardening books that previous experts have written, so they are regurgitated opinions rather than independently supporting opinions. Anyone still in doubt is welcome to come and see my 2000 or so rainforest plants and check them for evidence of phosphorus poisoning.
OK - I can get Grevillea for $2.50 at the Rocky markets - I'll go out this weekend and buy 3 or 4, plant them in full sun and give them the same high phosphorus fertliser that the rest of other plants in that bed tolerate (Pandorea, Ixora, Gardenia and Syzygium Cascade) - will report back in a month or so.
Yuruga native nursery suggests using CK 77 or similar, or a lawn fertilizer with a phosphorus ratio of less than 3 - apart from the particular brand they mentioned (I don't remember what it was) this can be difficult to find, though.
Hell's bells - don't you guys get it. proteaceae are NOT a homogeneous group. This forum has been clogged up with people comparing apples with mangosteens, and quoting experts talking aboutr things other than the topic of discussion.
Know your plant, know its individual required growing conditions, and you will succeed. If God had meant one rule to fit everything, He wouldn't have created 257,839 different plant species.
Interesting that we seem to be discussing the effects of getting the maximum growth out of our plants by applying added nutrients, when they may not be needed in a lot of situations.
We tend to want our gardens to grow as fast as possible and the solution we turn to is, more nutrients! I do bother that we often apply far too much nutrient onto our soils to maximise growth but are unaware how much is not being taken up by the plant and ends up as runoff in our waterways. I am sure I am guilty of it myself sometimes.
When it comes to rainforest plants, it seems to me that soil moisture is equally important to maintain optimum growth. So a good deep water will boost growth just about as much. Okay, okay, I realise it depends on the situation as soils vary greatly but the last few years have been unusually dry and my rainforest has significantly responded when we have got good downpours.
Pouring on soluble nutrients is not always the best idea as some is bound to get into the runoff. I remember a great saying in one of my Environmental Horticulture classes: "There is no away".
I totally agree. Plants in the wild get their nutrients from leaf mulch, etc and put on their best growth in the wet season (when we have one that is :) ) or after good rains. Too much plant food leads to lots soft growth prone to disease and insect attack. The only things that go on my plants are mulch and the natural leaf fall.
About 6 mths ago we planted quite a few syzigiums (different varieties) and similar that have only had rain (average less than 25mls month) except for the first few weeks, and these plants are easily 5 times their original height.
Once asked the leader of a Green Corp or equivalent what the benefits were of their using fertiliser on indigenous spp on good scrub soil. She got defensive and couldn't give a straight answer. Was it because the result produced a better "outcome" for a report? I could see the new roots hanging about the lollyshop instead of seeking their own tucker.
I think loosening that sq metre of top soil about the new planting pretty important, as is keeping that sq metre quite free of competition until the tree roots are well away. Good mulching and good watering practices complement each other.
Mate, I'm not about to let my ignorance stand in the way of my experiment ! Prior to this thread, I was giving my rainforest plants very little beyond some fish and seaweed (OK, a little blood and bone), but now I feel compelled to expose them to a host of commercial fertilisers in the hope that I'll be able to prove my point (what *was* my point again ?).
OK, team, I admit it - I've committed the unforgivable and mixed exotics in with my natives, palms in with cordylines and crotons amid lillipillies. I've got pine bark mulch leaching nitrogen from my soil, and large palms extracting whatever remains : without the natural leaf litter I hope to have in a few years, surely I have to do something to feed the soil ? My compost wont break down fast enough to feed this many plants, so I'm left with Nitrosol and Osmocote and Garden Gold and Dynamic Lifter and ...
Ahem, where was I ? Oh, the grevilleas are doing fine in their new location, so the residual fertiliser hasnt harmed them. I'm still predicting that Osmocote will poison them, but it will be interesting to see if there is any decline prior to that.
Certainly nothing wrong with experimenting, after all that's how we learn.