Untitled Document

OrchidSafari
Plant Nutrition etc
Moderator: Bert Pressman
Wednesday Oct 3rd, 2001

CARE AND FEEDING OF ORCHIDS

Bert Pressman

Many orchid enthusiasts pass along various unsupported cultural myths as if they were divine revelations of truth. Their zeal is not diminished by the hearsay nature of their advice. Thus a recent guest speaker at a Miami club meeting claimed that orchids have no need of the nutrient MAGNESIUM. This motivated me to compile a rational basis for advice about orchid fertilizer application.

A convenient starting point is a recent [1998] technical book with the jazzy title “The Physiology of Tropical Orchids in Relation to the Industry.” It provides chemical analyses of several orchid tissues. Without going into the specific function of the various components of orchid tissues, it reports that different orchid species and tissues have essentially equivalent mineral composition, and it follows that every ingredient listed in the table below, must be supplied by fertilizer, if orchids are to grow, prosper and flower.

Typical Composition of Dry Orchid Tissue by Percent:
Leaves: Nitrogen,1.8; Phosphate, 0.2; Potassium, 4.2; Calcium, 1.3; Magnesium, 0.5; Iron, 0.01.
Roots: Nitrogen, 2.0; Phosphate, 0.3; Potassium, 2.2; Calcium, 0.8; Magnesium, 0.8; Iron, 0.04.

We are familiar in general with the three number designation of commercial fertilizers for Nitrogen, Phosphate and Potassium, e.g., 20-20-20. In a balanced fertilizer, the phosphate would seem disproportionately high, but it is not absorbed as efficiently as the other elements. We needn’t be concerned with calcium, since our tap and well water percolates through limestone before it hits the orchids, and picks up just enough calcium to satisfy our plants. Orchids also need low levels of the trace elements iron, manganese, zinc and copper, but these are amply supplied as impurities in the gray-brown, technical grade chemicals used in fertilizers. That accounts for everything except the major component MAGNESIUM.

The “Leibig Principle”, a concept developed by the father of agricultural chemistry during the 19th century, states that the lack of any essential nutrient is equally capable of limiting plant growth. Thus if you don’t want lack of magnesium to limit the growth and flowering of YOUR orchids, I recommend adding ½ teaspoon Epsom Salts [magnesium sulfate, get it at your pharmacy] to each gallon of fertilizer solution, EVERY time you fertilize.

Other, more succinct cultural recommendations:
1. There is no theoretical or experimental support for the myth that high phosphate fertilizer favors flower initiation. Kerry’s Bromeliads has checked this possibility exhaustively with negative results.
2. Minerals are absorbed by orchid LEAVES as well as by roots. Accordingly, a detergent should be added to fertilizer solutions so that they coat leaf surfaces entirely and evenly without beading. This will also minimize spotting by calcium residues as the beads concentrate and dry.
3. While orchids absorb nutrients better under acidic conditions, and ground filtered water is usually alkaline, do not be concerned, since all commercial fertilizers are designed to maintain optimal acidity, even if alkaline water is used to dissolve them for application. This is true for all of a half dozen commercial fertilizers I have personally tested.
4. Your water can be too pure! If you use rainwater, RO water, or your tap supplies surface water, you may not be providing enough calcium or magnesium for optimal growth. Consider using a Cal-Mag fertilizer.
5. If you fail to flush your orchids periodically, as water evaporates, salts will concentrate and may become toxic. Conversely, if flushed too soon after fertilizing, orchids may not absorb optimal amounts of nutrients.
6. While most of the salts, which occur naturally in water, are beneficial to orchids, beware of salt incursion showing up as elevated SODIUM. A second source of detrimental sodium levels could be commercial water softeners, which exchange desirable calcium for toxic sodium.

Orchidglade
The commercial fertilizer I was referring to in the handout is a Peters product: Excel Cal-Mag. It is a 15-5-15 with calcium and magnesium supplement.

Pecteilis in KY
Man after my own heart! When I recommended feeding magnesium salts a year ago they all thought I was nuts! I feed epsom salts at least four times a year. You recommend every feeding? How does that effect the fertilizer? Does it cause any precipitation?

Cattdan
Bert...I still think catts can utilize more urea than we think! Even though I use a fertilizer with no urea. I see others using high urea fertilizers and the plants look wonderful. I know the subject has been argued to death...Nuff said!(GRIN)

Ernest
Bert, if you recall, Sugundo said that he uses 1 tbs per gallon of epsom salt every feeding, what are the effects on the plants when such a high concentration is used? How is the amount of light that a plant can take affected by it if at all.

Orchidglade
Since you feed Nitrogen and Potassium continuously through the year, it only makes sense to feed magnesium regularly as well. It seems to dissolve in even concentrated fertilizer solutions without difficulty. Ritter orchids claims to use 2 tbl/gal I don't believe it but some excess magnesium does no harm - except in the pocketbook

Pecteilis in KY
In cool weather I have found a layer of crystal slush in the bottom of the fert. bucket some times. I have no idea what it is. Only when I combine epsom with Peters.

Cattdan
Potash has a tendency to salt out below 50 degrees. I'm unsure of the trace elements.

Orchidglade
Since the trace elements are in low concentrations, you certainly don't have to worry about them salting out. Salts dissolve more poorly in cold. As long as its a mixture leaving sufficient good things behind in solution, probably produces no bad effects. Epsom salts themselves are very soluble. In Florida it never gets cold enough to cause problems.

Pecteilis in KY
Have you heard the argument that you are really feeding the indemic fungii, not the plant directly?

Orchidglade
That can't be the whole story since orchid foliage can absorb nutrients directly p and they are presumably fungus free (if you're lucky, that is)

Cattdan
Bert...I've always been told that Phosphorus is hard to be taken in through the foliage.

Pecteilis in KY
I had read someplace, the repository of all "known" facts, that plant tissue does a poor job of utilizing elemental minerals direct. That the fungii convert it to an organic that the plant can use.

OrchidGlade
I have no facts, but I suspect neither does your repository. I am reasonably certain that orchid roots as well as foliage absorb nutrients directly

Pecteilis in KY
There is a difference between absorbing and utilizing.

Orchidglade
Technically, yes - but plants cannot use what they do not absorb.

Mary Lou
I was always taught that plants cannot utilize the direct organic matter and needs to have that broken down into its elements first.

Orchidglade
That's certainly true for fish emulsion, but I don' thing it applies at all to nitrate or ammonium

Cattdan
If your feeding Peter's Peat Lite at 100 PPM....and it shows Magnesium .28 PPM at that dilution...is that enough? I use Peter's Peat lite 20-10-20

Orchidglade
Sounds awfully low - about the level of impurities, and orchids need magnesium big time

Cattdan
Hmm...sounds like I'll be trying to get some epsom tomorrow!(GRIN)

Mary Lou
Doesn't Dynagrow have enough magnesium in it?

Orchidglade
So I've heard; I thing they use Calcium Nitrate as a source of nitrogen, but I don't know for a fact

Mary Lou
Is it OK to add Physan to your fert?

Orchidglade
Good question. Used to and found the fertilizer caused an oily impurity to come out of the Physan. The problem was that the oil couldn't be removed by anything and gunked up the hose-end sprayer. But I got away with it for a year

Cattdan
I use Physan from time to time...and I put it in my fertilizer....don't go too heavy with Physan....follow the rates closely. It can get hot and burn plants if overdosed!

Ernest
How about Dithane M-45 (mancozeb)?

Cattdan
Ernest....do you use Diathane much? I noticed Carter and Holmes seem to use it when needed? What are you putting it on?

Ernest
I have put it on every plant I have exept the paphs. I have used it for two years now and have...only in the beginning though...exposed myself to it DIRECTLY ect... I have only put soap in it till now and I use it when I get fungus only, since I put a fan I have not seen any sign of fungus but if I do get it I want to know if I can mix it with Dithane

Cattdan
Ernest...I sell Ag Chemicals for a living. If it will mix and not turn into mayonnaise type paste...it's OK. Test in small quantities first...but I'd bet money it will be fine even with soap! I use small amount of soap every time I fertilize. It wets the plant better!

Orchidglade
I'd go along with that - but I was surprised by my bad experience with fertilizer and Physan. It may well be that some batches of Physan are purer than others

Cattdan
I think Physan and Consan Triple Action 20 are the same product...I never knew why two different companies made the same product, but called them something else! Both are used for everything...They even spray locker rooms down with it to control athletes foot!

John in Arcadia, So Ca
Physan used to be called Consan but had to change the name because of a trademark conflict. I knew the son of the manufacturer and that is what he told me.

Cattdan
It doesn't surprise me about the lawsuit or that it can be used as an algaecide. When I mix fertilizer in a plastic barrel I have, if I add Physan...the algae...goes by by!(GRIN)

Orchidglade
Some one once persuaded me to get some magic barn wall cleaner for my orchids. I read the lable and it, too, was the same as Physan and Consan. Swimming pool algaecide is also the same

Zeynep
Bert, if I am not mistaken, aren't there two kind of Swimming pool algaecide. Which is the one can be used on plants?

Jim4eq
calcium hypochlorite, NOT the sodium type. *G*

Cattdan
You surely don't want Chlorine or Bromine on your plants....It comes in a small bottle and would almost bet they charge and arm and a leg for it...I need to check!

Orchidglade
I do believe there are mercury or silver based algaecides - which would cause nothing but grief for plants - what you want is "quaternary amine" type algaecides - but why not simply buy Physan?

Mary Lou
The RD and Physan are similar but have different chemical in them. You can use a strong Physan to bleach anything without the fumes etc of Clorox. Similar to the chemicals used in hospitals to sterilize tables etc.

Orchidglade
Actually, I think you would find that the non-ionic detergent, Triton, is very chemically inert, and doesn't bleach anything

John in Arcadia
Consan/Physan was originally used in Hospitals for a strong disinfectant. They even once said that Consan would kill viruses but soon stopped that.

Mary Lou
I do believe that in strong dilutions these chemicals do kill viruses on tables etc., certainly not in a plant. It would burn the plant up to use it that strong.

Stumpy
Only way to kill viruses is throw everything in the garbage.

Orchidglade
If you want to kill viruses on contact, nothing beats good old Clorox - at about 1-5 dilution

Charlotte_in_Calif
That is very strong. In veterinary medicine we recommend a 1:30 dilution to kill viruses. I presume you are talking about the household Clorox and not the Clorox for industrial use?

Orchidglade
Actually, I use 1:10 swimming pool chlorine (calcium hypochlorate) which is twice as strong as Clorox

Ernest
Would a stronger solution kill viruses more quickly on benches? How long will it take to kill a virus on the surface of the plant once the dilution is sprayed?

Orchidglade
Unfortunately virus infections are within cells, and you can't kill the virus without killing the cells! I don't think I would recommend SPRAYING chlorine DIRECTLY on plants, but a jar of dilute bleach is great for disinfecting cutting tools on contact; beats hell out of trisodium phosphate which takes several minutes

Janetteh
If the bleach solution is not stronger than 20% it probably won't hurt the plants. I think that Wilford Neptune sprays the inside of his greenhouse with this solution twice a year to get rid of algae and he said that it has never hurt the plants.

Zeynep
I spray the walkways, under the tables, walls and part of the glass with Clorox, and after 1 hours, I rinse everything. This is for algae.

Charlotte_in_Calif
Mary Lou, what varieties of orchids do you spray with Physan? And why are you spraying? Do you have fungus on the leaves or in the media?

Mary Lou
I spray my Phals especially as well as Vandas and other things with the Physan because we often get long heavy rains here in Miami and it cleans up things and prevents fungus from getting control. Works better if you use it before an infection. Don't use it all the time. After cold and wet in winter is a good time. But, see, we grow outdoors here. You do have to be careful and use a weak dilution of Physan.

Charlotte_in_Calif
Is there a resource anywhere that tells you which chemicals are ok to mix? Something that takes into account interactions and pH differences etc.?

Mary Lou
My old garden center used to have such a chart, a big one on their wall, but I have not seen that for years. Generally I don't mix much but do like to combine the Physan and Fert for convenience sake. I also use just a simple hose end sprayer.

Orchidglade
Most plant preparations can be mixed, but if I generalize too broadly, someone is bound to come up with exceptions

Jim4eq
Yeah, silicon is a pain!

Zeynep
Also, the exceptions are noted either at the instructions or MSDS....

John in Arcadia, So Ca
Instead of soap, can you use something like WaterIn, which breaks down the surface tension of water.

Cattdan
Actually we sell them all....I just have Dawn soap handy. Our 90% nonionic is actually better...no foam...and yes I can get it free. I just forget.

Mary Lou
How about adding the soap to Jerrys Grow?? I have some JG here that I will be using soon but didn't know about the alcohol content mixing with soap or etc.

Cattdan
It's not a problem with JG. I use Jerry Rodders Wundergrow from time to time. I use soap as a wetter all the time, including insecticides and fungicides. You want good contact...not beading and running off! Jerry and I are good friends....It's just easier to get Peter's Peat Lite locally in Texas!

Orchidglade
I have been using small amounts of a surfactant for years - Triton X-100. It can be gotten from a chemical supply house, but I don't know of a more general source; if you can get it, it's great

Cattdan
If you don't have an ag chemical dealer locally...some feed stores may have something similar! Watch the Triton. I used to work for Rohm & Hass that makes it. It's great at recommended levels, but............if you go too wild with the dose it can burn.

Orchidglade
Yes, it is the Rohm & Haas product. I use 3 ml [about 1/2 tsp] per 20 gallons delivered from my hose end sprayer, and it does a marvelous job; everything gets coated evenly

Cattdan
Bert...we did test with Triton on corn...if the level of Triton got too high...it can burn.....at the rates you use....it's a great product....just don't do like some people....more is better!

Mary Lou
Is anyone using the silicon sprays with success?

Orchidglade
Mary Lou, I found out from the Dade water guys that our tap water is LOADED with silica. What good do you expect from spraying a little more on them?

Cattdan
Silicates surfactants spread much better...the problem is the cost....We only use them in the Ag field when we have to. a 90% nonionic is about $16 a gallon. A silicate like our Silkin is $60 a gallon. You use half as much, but.....the cost. I doubt you have anything you use in the greenhouse that would benefit from a silcate type surfactant!

Stumpy
We use a lot of chook pellets here ie hardcanes catasetums anything that is leafy only a couple of pellets though that or blood and bone

Orchidglade
What's a chook pellet?

Stumpy
Chook is fowl manure. I know its strong but it is a very good booster for certain plants. In pellet form. Haven't they got chooks over there? [*G* --KB]

Janetteh
It is strong if it is fresh. After it has aged, it won't burn plants but will really make them grow.

Cattdan
Years ago...I used fish emulsion...and it STINKS! Using chicken manure on my catts is OUT!(GRIN)

Orchidglade
Why should manure, which requires breakdown and can't be absorbed by foliage, be better than nitrate or ammonium? I think its an example of human instinct - if it's unpleasant it must be good for yoou - or your plants

Jim4eq
And it's how the plants get fertilized in the jungle, bird and monkey pellets. *G* I think Caroline also has lizard pellets out in Oregon!

Orchidglade
But man has come a long way from the jungle - or at least some of us have

Janetteh
If the manure is mixed in the medium, it would give you a steady supply of nitrogen over an extended period of time. Some orchids would respond to this and others wouldn't. Would probably not be a good idea to mix the manure in bark as it is mostly urea. But in a peat based mix or a terrestrial mix, it would work just fine. Is about the same as top dressing with blood meal and bone meal on phrags, which a lot of people do twice a year.

Kathy_in_N_Calif
Koopowitz did a series of experiments in Africa where they studied the amount of NPK etc excreted by a tree's leaves after a rainfall. Found that an amazing amount of stuff is excreted that way, in addition to storage in the heartwood. That a tree's leaves 'leak' and this leakage is not diminished with a prolonged rainfall, nor is it due to the leaves being washed off of their nutrient rich dust. (He controlled for that) So this relatively constant leakage takes a bit of the guesswork (in terms of when the next monkey or bird will pass by) out of the epiphyte's nutrient equation.

Trees feed their orchids weakly, weekly...

Ernest
Do plants in more sunlight abosorb less fert thru their hard leaves and toasted roots (vandaceous)?

Sharon_in_Indiana
Just got through reading an article in the new Orchids mag about aspirin and orchids. Has anyone seen it yet? The article was about using aspirin at 3/4 tablet per gallon of water once a week with the fertilizer and a squirt of Whisk or Dawn. The statement is made "Our plants have more blooms, bigger growths and fewer fungal problems since aspirin became part of our culture." What do you think about this?

Cattdan
Is there any research data to support the results...with a control? I'm not arguing...just curious! You'll have us all running to the store in the morning and buying out all the Bayer!(GRIN)

Sharon_in_Indiana
The only research mentioned is the person's use of aspirin on 2000 orchids over the last year, evidently compared to past year's results.

Steve in Adirondacks
Without a controlled study, it's pretty much just a superstition.

Orchidglade
While I didn't read the article myself, someone quoted it to me tonight. The claim is that 3/4 aspirin good, whole aspirin bad. If that's what the article truly claims, it's ridiculous on its face. Coming from a research background, it would probably take at least $50,000 worth of labor and materials to prove such a statement statistically. That sounds like a typical anecdotal bit of advice that is offered so freely, and worth little. Was climate held constant. What about bugs and diseases - were they controlled? I am not persuaded to use aspirin except for my headache plants

Cattdan
Bert...in the ag business...we see so many Vodoo products yearly. You would think over time...all the schemes would be exhausted.........but not so! Buyer beware!

Jim4eq
Didn't they used to say that about willow bark? (the original source of salycilic acid) Sometimes the voodoo has a basis in fact which just hasn't been proven yet. Look at tamoxifen, took years before it was pursued since not a patentable product. Then they tinkered with it enough to gain a patent, and voila, that little piggy went to market.

Cattdan
While I agree with you....I know flim flam when I see it. The data they present is so sketchy at best! Yes there are many good new things coming out.....it's just there is always a bit of junk as well! Just be careful. The major name brands are OK...these fly by nighters.....just be careful!

Jim4eq
Oh, I totally agree. There's a lot of snake oil out there, but there's sometimes a reason why all those wives are old enough to tell tales, *G*

Kathy_in_N_Calif
This is from Volume One of the Orchid Guide Digest, researched by Bruce Pickholtz, Coral Springs, Florida

[quote]
George Norris' question about using willow tea/salicylic acid to promote root growth prompted me to poke around on the web to see if there was anything out there on the subject. To my wonder and amazement, there exists a number of LEGITIMATE articles and papers about this - and they are absolutely fascinating.

Please bear with me as I'm not a scientist, but from what I can gather Salicylic acid (SA) is produced by plants in response to an attack by microbial pathogens (converted from cinnamic acid - - tying this also to the use of cinnamon as an antibacterial/antifungal), producing a hypersensitive reaction (HR) in the area around the infection, killing the plants' cells around the infection, preventing its spread, as well as the pathogen as well. Apparently it does this by producing heat! SA, as it turns out, is also the substance responsible for the heat production in Arum flowers (skunk cabbage) that can raise the temperature of the flower as much as 14deg, according to one source (I'm not sure about that number). Following the HR, the SA then appears to confer a lasting "systemic acquired resistance" (SAR - mentioned in a previous post) to pathogens in general. The pathogens included bacterial, fungal, and VIRAL.

SA production was also noted as a response to cold and drought. There appears to be a significant body of evidence that suggests that application of salicylates can, in fact, promote virus resistance. See: http://waksman.rutgers.edu/Waks/Klessig/klessig.html

As if that's not interesting enough, there's lots more to this. A Rutgers Univ. study seems to show that some of the SA is converted to the gas methyl salicylate and released to the atmosphere where it is converted back to SA by neighboring plants, bolstering their defenses as well. http://ci.mond.org/9705/970508.html

Also, use of SA was cited as promoting bud development, enhancing longevity of flowers and inhibiting ethylene biosynthesis. All of keen interest to orchid growers. Seems too good to be true. Again, I'm no expert but I kept only to what appeared to me to be reliable source material.

As to George's question, I can only surmise that the application of salicylates could trigger the plants to act in a manner that would help it cope with a potential threat. I would think that increased root production would be a logical response.

Now I would ask that somebody who really knows what they're doing look at this stuff and provide their insights, not to mention a more coherent summary.