# Question About Fertilizing



## wilbeck (Nov 16, 2006)

I have been fertilizing my paphs about every two weks with a weak solution (currently of Hauserman's Fertilaide Fertilizer liquid 15-5-5). Unless they are in bloom or spike. I use mostly dehumidifier water, with the occasional drink of local tap water, which is pretty hard. Prior to using the Hauserman's liquid fertilizer, I was using dilute (quarter-strength) Peter's balanced fertilizer. Copuld I be doing better? I haven't killed anything yet. Should I be fertilizing while the plants are blooming? Thanks for any advice.


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## bwester (Nov 17, 2006)

I use 150ppm MSU fertilizer every time I water, but I grow in S/H so they are always in it.


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## Heather (Nov 17, 2006)

I fertilize all my plants 3 of every 4 waterings. Usually I flush the plant with plain water first, and then again with water with 150 ppm of MSU fertilizer (and a little protekt and KLN in the mix). My plants are grown semi-hydroponically.


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## NYEric (Nov 17, 2006)

Heather, do you leave the fertilizer in your S/H then?


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## Rick (Nov 17, 2006)

This is a question that will be all over the board.

Presently I don't do semi-hydro (well maybe for a few phrags unofficially).

I use the 1/2 strength MSU fertilizer + superthrive + enough proteckt to increase the pH to 6.5 to 7.5 in RO water.

I fertilize 1 X per week, which is 1 out 3-5 waterings for potted orchids and 1 out of 7 waterings for mounted orchids. All other waterings are with RO water.


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## aquacorps (Nov 17, 2006)

Heather, is the 150 PPM nitrogen or the TDS of the MSU fertilizer? Rusty


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## Heather (Nov 18, 2006)

nitrogen I think, Rusty. (I just use the directions on the bottle for 150ppm so I think that's nitrogen (I'm lazy and not getting up to look at the moment...)


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## TADD (Nov 18, 2006)

I do not fertilize ....ssssshhhhh.... Maybe that's my problem.


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## patrix (Nov 18, 2006)

I read that Venustrums aren't calcerous (sp?) species, does that me I shoudl not use cal-mag?


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## Rick (Nov 18, 2006)

patrix said:


> I read that Venustrums aren't calcerous (sp?) species, does that me I shoudl not use cal-mag?



No all plants need some calcium. But I would not put them in a potting mix that keeps the pH in the mid 7's or higher. (This would be done with the addition of lime or oyster shell and the like).


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## likespaphs (Nov 19, 2006)

i've noted which of my paphs are big on calcium and fertilize on one of every three or four ferts with cal mag

i've always wondered if you cross one that likes calcium and one that doesn't, which need wins out or is it just that the need for calcium decreases?


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## Rick (Nov 19, 2006)

likespaphs said:


> i've noted which of my paphs are big on calcium and fertilize on one of every three or four ferts with cal mag
> 
> i've always wondered if you cross one that likes calcium and one that doesn't, which need wins out or is it just that the need for calcium decreases?



I think the "need" for calcium is pretty much the same for all paphs. What varies is the pH environment that various species prefer. The term calcereous or calciolis just refers to the species preference to grow on calcium (limestone) rich substrates. Although these substrates are rich in Ca (the bioavailability is debatable) they are also strongly buffered substrates that keep pH from drifting too low, as what generally happens in more oganic (humic) substrates. The pH of the substrate drastically alters the forms and availability of macro and micro nutrients in our fertilizer mixes. 

I would suggest that if you do use a calcereous addition to your potting mix, then the nitrogen source in your fertilizer mix should be primarilyfrom nitrates rather than ammonia since ammonia becomes toxic as pH goes up from the mid 7 range.


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## wilbeck (Nov 19, 2006)

Thanks for the advice and discussion. It appears that I should keep fertilizing while the plant is in bloom, perhaps more often, and that I need to get some MSU fertilizer. Ah, but from where? I won't be using hydroponics (semi- or whole) anytime soon. I would need to learn a lot more. Does the occasional watering with our local hard well water count for much as regards the need for calcium?


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## Rick (Nov 19, 2006)

I get my MSU (for RO water) from Robert's flower supply (orchidmix.com). He also carries the MSU mix for tap water. But there are other sources too.

Actually folks use all kinds of brands of fert. I just got one that works well for me, and I'm going to stick with it for a few years before I decide there is something better.


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## NYEric (Nov 20, 2006)

*Question*

I dont know anything about MSU fertilizer. Can you use it in R.O. water w/out getting salt build-up?


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## Rick (Nov 20, 2006)

NYEric said:


> I dont know anything about MSU fertilizer. Can you use it in R.O. water w/out getting salt build-up?



There are two types of MSU. 1 for making up in RO water that has calcium and magnesium added, and 1 for making up in tap water that is lacking in cal mag.

The cal mag in most tap waters is fine for orchids and doesn't need to be added twice in a fert mix if not needed.

Any inorganic based fert mix has the potential for salt buildup, but if you use RO (or rain, or distilled) water as your primary source water you will tend not to build up salts.


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## SlipperFan (Nov 21, 2006)

wilbeck said:


> ... and that I need to get some MSU fertilizer. Ah, but from where?


Porter's Orchids carries both the tap/well water and the RO/rain/distilled water versions.


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## NYEric (Nov 21, 2006)

Thanx for the info.


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## Heather (Nov 21, 2006)

Kelley's Korner is now carrying both as well.


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## Marco (Nov 22, 2006)

Antec has a great list on which paphs need calcium supplement. http://ladyslipper.com/calsub.htm

Just to add a bit onto the fertilizing question. What's the difference with fertilizers with and without urea?


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## Rick (Nov 22, 2006)

Marco said:


> Antec has a great list on which paphs need calcium supplement. http://ladyslipper.com/calsub.htm
> 
> Just to add a bit onto the fertilizing question. What's the difference with fertilizers with and without urea?



Thats not really a list of species that require calcium supplements, but a list of species that are found in association with calcareous environments. Refer back to my post on pH.

Urea is a nitrogen yeilding molecule that is somewhat more complex and less bioavailable than ammonia. Some orchids apparently find it difficult to consume and sometimes toxic. Ammonia and Nitrate are the easiest nitrogen forms for orchids to utilize. Ammonia can be toxic at pH levels from 7.5 and up. So if you wanted to buffer up the fertilizer mix for a roth to duplicate the ultra basic conditions of serpentine (the geology that roths are found over) the pH could be greater than 8, and you should use a nitrate based fert rather than ammonia.


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## gonewild (Nov 22, 2006)

Rick said:


> Urea is a nitrogen yeilding molecule that is somewhat more complex and less bioavailable than ammonia. Some orchids apparently find it difficult to consume and sometimes toxic. Ammonia and Nitrate are the easiest nitrogen forms for orchids to utilize. Ammonia can be toxic at pH levels from 7.5 and up. So if you wanted to buffer up the fertilizer mix for a roth to duplicate the ultra basic conditions of serpentine (the geology that roths are found over) the pH could be greater than 8, and you should use a nitrate based fert rather than ammonia.



Urea is used as a cheap source of Nitrogen for fertilizer mixes. Urea is not well suited to fertilizer mixes for container grown plants. 

The Nitrogen in Urea quickly converts to ammonia gas and is released to the atmosphere unless contained by the soil. In an orchid mix which is normally very course, loose and has an atmospheric air flow, nitrogen from Urea may not be available to the plant. The Ammonia gas quickly leaves the potting media to escape upward to the atmosphere. So with fertilizers containing Urea you may not actually be getting much nitrogen available to your plant. Or too much).

I suppose the toxicity you refer to with orchids may actually be a reaction to the the ammonia gas by the orchid root?


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## Rick (Nov 24, 2006)

gonewild said:


> Urea is used as a cheap source of Nitrogen for fertilizer mixes. Urea is not well suited to fertilizer mixes for container grown plants.
> 
> The Nitrogen in Urea quickly converts to ammonia gas and is released to the atmosphere unless contained by the soil. In an orchid mix which is normally very course, loose and has an atmospheric air flow, nitrogen from Urea may not be available to the plant. The Ammonia gas quickly leaves the potting media to escape upward to the atmosphere. So with fertilizers containing Urea you may not actually be getting much nitrogen available to your plant. Or too much).
> 
> I suppose the toxicity you refer to with orchids may actually be a reaction to the the ammonia gas by the orchid root?



Urea doesn't breakdown spontaneously and needs a fair amount of help from bacteria and bluegreen algae to be utilized by most plants. Thats why its fairly useful for crop plants like soya beans and rice, but not real helpfull for most orchids. If your potting mix is dense with lots of bacterial action to it, then you might end up with an excess of ammonia, which could ulitmately be toxic to the orchid.


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