Peter's Cal-Mag Excel
 

I recently read an excellant article in the February '08 issue of 'Orchids' about the use of a fertilizer named Peter's Cal-Mag Excel (15-5-15). I would like to try this fertilizer, but cannot find a source for it. Does anyone know where this product can be purchased? Thanks for any info

Silkus,

I am not of much help here, but am just interested in any feedback you receive. I newly bought a RO Filter and have been doing some research where to get a good fertilizer for RO water. The only one I have found so far is Peter's Excel 13-5-20 and 15-5-15...

I would be interested as well. Also I could not find a source for the S.T.E.M.

But the author has an email address:
remarkorkid@aol.com
maybe he could tell us.

HortHippo.com has a 25# bag of 15-5-15 for $31.00
I did a search on there site ("Peter's Cal-Mag Excel") and found it listed on the second page.
Also here is a website that has alot of research on fertilizer in R/O water on orchids.
Fertilizers in Reverse Osmosis Water

Jayme

Interesting, here in Brazil (a "little bit" far from Canada than US) Peters (any kind) is easily found! And is cheap too! (Excel Cal-Mag 15-5-15 ~ U$ 8.73 - 2Kg pack).
A tip for Calcium absorption: this element is poorly absorbed in foliar fertilization, and do not move into the plant when asorbed by leaves; when using Cal-Mag, you need to watering the plant with the fertilizer solution.

That stuff has a formula very close to that of the Greencare Orchid Special for RO water (aka "MSU Fertilizer"), so that is a decent alternative.

I carry Peter's STEM.

A follow up on that last post - orchids are basically very poor foliar feeders in the first place. As part of a water-retention strategy, they have evolved to having very few stomata on the upper leaf surface, and some even close them in the daytime.

:hijacked: sorry

Ray, how do you control the pH of your RO Water after adding the fertilizer? In one of the previous replies in this thread is a link, where it is shown that the pH of the water stays quite acid when using Peter's Excel...

In the case of the Greencare Orchid Special for RO - the formula close to the Peter's Cal Mag - the minerals are formulated specifically to give you high 5's/low 6's, so no additional adjustment is necessary.

I have always used Dyna-Gro Pro-TeKt to raise the pH if I had to with other fertilizers.

Hi Ray,

thanks for the reply. You mean high 5's/low 6's at around 150 ppm N, right?
I have not yet started with RO, as my filter will arrive by next week. Just after I need to install it and start checking how it works with the Peter's Excel... probably, I will need to test the pH a couple of times until I get it on the right range...

With the Greencare MSU RO fertilizer, the pH is going to be fairly independent of the concentration