ProMix HP question

woohoomanApril 15, 2014

So, I was at Home Depot and noticed they started carrying ProMix HP. HAD to pick some up just because I've heard such great things about it. KInd of pricy though -- 25 bucks for a 2.2 c.f. compressed bale!

Anyhow, I don't get it. It's a container mix but has mychorrizae in it. Most container people will tell you that pots aren't a good place to build a microherd. (Though, I think my large oak barrels do an ok job. I find worms in it, so they must like it,, It's a mix of potting mix, compost, a bit of peat, and perlite. I also use organic meals in them).

But here's some questions regarding the ProMix HP

So why the fungi in a container medium if not a hospitable place for them?
Do I use it straight up?
Do I add some compost?
Should I mix it in some 5-1-1? At what ratio?
Organic ferts or conventional? Wouldn't the conventional be bad for the mychorrizae?
Any need for lime or gypsum? My water is at 8.1 ph
What's the ph of it straight up?
If I was to use straight up, should I add a bit more perlite?

Here's one that really gets me --- Like I said, heard great things about it, but it consists of like 75% sphagnum. Not the best word in the world when hearing some of you talk about container mixes, especially at that ratio.

See what you guys/gals can do in answering some of my questions. I want feedback! ;)



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seysonn(8a WA/HZ 1)

Hi kevin. Good to see you here.

ProMix is supposed to be a stand alone potting mix just like any other potting mixes, such as MGMC.

ProMix is fundamentally is a peat moss based mix(you already mentioned that yourself). That is why they can compress it. Peat moss sold for less than half that price. Other obvious ingredient is perlite. The company that makes ProMix is also a peat moss marketer.

You can add microherd to any potting mix bt adding good compost.

Off the bat, being peat moss based, promix should be on the acid side (maybe 6 + ?)

You can reverse engineer Promix: 70% peat 15% perlite 15% compost. There you go. Now you have your own brand new 5-1-1. Or call it 1-1-5 or 1-5-1 , at about half the price.

    Bookmark   April 16, 2014 at 6:03AM
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greenman28 NorCal 7b/8a

Plenty of organisms and fungi will colonize container mixes, however the fluctuation in temperature and moisture is what limits the population. That's why organic techniques don't work as well in standard nursery containers.

Once containers pass a critical size limit, the temperature and moisture levels are more buffered in the mix, which allows the microherd to thrive. This is why I use organic nutrients in my 15-gallon tomato pot and my half-barrel fern container.


    Bookmark   April 16, 2014 at 12:05PM
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Josh: Any more thoughts on my other questions?



    Bookmark   April 16, 2014 at 2:57PM
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greenman28 NorCal 7b/8a

Not really sure, having never used this product.

I think it's always a good idea to add more Perlite to these kinds of off-the-shelf potting mixes. I'd most likely add some 1/2-inch screened bark, too, to stretch the mix even further (from an economic standpoint). I wouldn't add anything that would increase the moisture retention of the mix - I'd rather increase the container size. I think either fertilizer will work, with synthetic fertilizer having a decided advantage in small and medium containers.


    Bookmark   April 16, 2014 at 4:33PM
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HP is their fast draining mix. They take out some of the peat and add perlite, I don't think most growers would find it needs more perlite.

    Bookmark   April 16, 2014 at 4:54PM
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seysonn(8a WA/HZ 1)

My question is : Does it contain anything other than peat moss, perlite and compost ( they call it mychorrizae?) ?

You can do that to 5-1-1 , that is add some compost to make it microherd friendly.

The only reason for having micro organism is to break down organic fertilizer. With synthetic fertilizer you won't need help from micro organism because the nutrients are readily available to the plants.

    Bookmark   April 16, 2014 at 7:21PM
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Mycorrhizae is actually the symbiosis between root and fungus. So they are claiming they have added myco forming fungus spores. The fungus of a mycorrhizae act as root extensions, colonizing the soil and caring nutrients back to the roots. Literature suggests that plants with mycorrhizae are at an advantage in less than optimal conditions, but that where nutrients and moisture are plentiful, there usually is not a significant advantage.

    Bookmark   April 16, 2014 at 10:36PM
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Yes. Moreover, when nutrients and water are plentiful, the associations may not form to as great a degree if I remember correctly.

If you're attracted by the idea of mycorrhizae, you can buy them straight up and add them into whatever other mix you're using or to your garden bed. However, this is usually not necessary in the garden because they're widely prevalent and will colonize the roots in any case under favorable conditions (to their growth).

Not to throw cold water on your mix, but I am of the opinion that peat-based mix is peat-based mix. I would use it as the peat component in 5:1:1. Otherwise, I'd expect it to behave as any other peat-based potting soil.


This post was edited by maple_grove on Thu, Apr 17, 14 at 9:04

    Bookmark   April 17, 2014 at 9:03AM
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