What's in the nutrient solution?

[OrchidLoverSA]

Hey guys, I'm going to take the plunge and move some of my orchids to S/H. I'm going to use the plastic-pot-with-holes-and-a-resevoir-method. I'm just unsure about the nutrient solution, everywhere I read about MSU... If I can't find that, is it ok to use a general low urea orchid firtiliser at lower concentrations?

If yes, do I then use just as I would the normal nutrient solution, then just flush out once or twice a month with clean water? As I understand it, you always give orchids in S/H some form of nutrient, never just clean water (unless it's winter), or am I way off the mark?

[bellini girl]

Check out the Semi hydro forum..Lots of great information by Ray

[DelawareJim]

MSU fertiliser is quite common. I get mine from Ray
Nutrients

It's also available at repotme.com
Orchid Supplies from rePotme.com - Orchid Mix - Orchid Pots - Orchid Care - Orchid Fertilizer

And from Kelly's Korner
Fertilizer & Nutrients : Kelley's Korner Orchid Supplies, We offer everything to grow great Orchids!

Otherwise, any water soluble urea-free fertiliser will work.

Something to keep in mind is that MSU was not developed for s/h use and because PrimeAgra, Hydroton, and other LECA wicks so well I've found I need less ferts. I currently use Ray's MSU at 50ppm N (1/4 tsp per gallon).

Cheers.
Jim

[Orchid Whisperer]

General comment on fertilizers, rather than S/H, but urea-free is not really necessary. Orchids do metabolize urea by absorbing the urea molecule directly and metabolizing it internally (or they would not have the enzyme urease). Check out the research by Martin Trepanier, conducted on Phalaenopsis (easily found by Googling the author and genus).

[Ray]

Originally Posted by OrchidLoverSA

Hey guys, I'm going to take the plunge and move some of my orchids to S/H. I'm going to use the plastic-pot-with-holes-and-a-resevoir-method. I'm just unsure about the nutrient solution, everywhere I read about MSU... If I can't find that, is it ok to use a general low urea orchid firtiliser at lower concentrations?

YES

If yes, do I then use just as I would the normal nutrient solution, then just flush out once or twice a month with clean water? As I understand it, you always give orchids in S/H some form of nutrient, never just clean water (unless it's winter), or am I way off the mark?

It's not that rigid. I water with fertilizer every time. If you fill the pot to the top rapidly enough, it will be self-flushing. If you want to use plain water now and then, it's no big deal.

The only plants that should NOT get fertilizer in the winter are those that need that winter rest.

---------- Post added at 01:51 PM ---------- Previous post was at 01:45 PM ----------

Originally Posted by Orchid Whisperer

General comment on fertilizers, rather than S/H, but urea-free is not really necessary. Orchids do metabolize urea by absorbing the urea molecule directly and metabolizing it internally (or they would not have the enzyme urease). Check out the research by Martin Trepanier, conducted on Phalaenopsis (easily found by Googling the author and genus).

I have read the Trepanier study, and am not all that impressed with the techniques followed or the veracity of their conclusions. However, one thing I have learned more recently is that while urea uptake is very poor through the root system - polar species like nitrate and ammonium ions are preferentially absorbed - the converse it true of foliar absorption, in which the less-polar urea is absorbed more readily than are the ionized species.

However, when you consider the moisture-retentive cuticle many orchids have on their leaves, it seems to me that foliar is probably the less-prefered pathway for feeding them.

[Orchid Whisperer]

Regarding the Trepanier study, it is worth reading to form your own opinions. I found it pretty convincing. I've used urea fertilizers for years with good results.

[Ray]

I'm not arguing that urea is not usable, it's just a matter of efficiency of uptake. Plants with thick cuticle layers and those with mostly hidden leaf undersides, will be very inefficient at urea uptake, as the plasmodesmata that provide the absorption sites, are associated with the stomata, which are mostly on the bottoms of orchid leaves. Plants with less of a cuticle layer and that have all leaf surfaces pretty much exposed will do better.


Ray Barkalow
Sent using Tapatalk

[Orchid Whisperer]

Ray, for me, foliar uptake of nitrogen (leaf cuticle, stomata, etc.) is not really part of the picture, as I do what I can to avoid getting water or fertilizer on the leaves. I use a pump sprayer to direct water to the roots and media as much as possible.

[OrchidLoverSA]

Thanks for the answers guys, I repotted 5 orchids into S/H today, so fingers crossed...