Acidifying container medium

bkay2000(8a TX)September 14, 2012

I need to add some kind of acidifying ingredient to my containers. I have very alkaline water. On a diagnostic report, my plant was diagnosed as chlorotic. I have about 50 containers with a minimum size of 1 gallon (a real gallon, not nursery gallon) up to about 15 gallons. I do not want to add more peat, as I need good drainage. I read something about vinegar (with no specifics), but that's a lot of vinegar.

Can I just use ironite?

This is my potting medium:

3 parts pine bark fines

1 part sphagnum peat

1-2 parts perlite

micro-nutrient powder

(I use granular fertilizer in my pots and also miracle grow)


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nil13(z21 L.A., CA (Mt. Washington))

If the water is that alkaline, I would adjust the water not try to fix the water problem in the substrate. You don't have to use vinegar, you can use citric acid. You can get it in a concentrated powder.

ironite is pretty nasty stuff loaded with heavy metals. It's just iron mine tailings. I wouldn't even consider bringing that onto my property.

    Bookmark   September 14, 2012 at 4:29PM
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bkay2000(8a TX)

Exactly how do you think I can "adjust the water"?


    Bookmark   September 14, 2012 at 5:31PM
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greenman28 NorCal 7b/8a

Vinegar or citric acid.


    Bookmark   September 14, 2012 at 6:50PM
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nil13(z21 L.A., CA (Mt. Washington))

Let's start from the beginning.

What is the pH of your water?
What diagnostic report said your plant was chlorotic?
How often to you fertilize?
What granular are you using and how much per pot? How was it applied?

With pine bark fines, peat, and micro, your water would have to be ridiculously alkaline to get chlorosis. Are you sure it's not just nitrogen deficiency?

    Bookmark   September 14, 2012 at 7:11PM
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nil13(z21 L.A., CA (Mt. Washington))

Can you post a pic of the affected plant?

    Bookmark   September 14, 2012 at 7:12PM
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bkay2000(8a TX)

I'm not sure of the ph of our water. I can't find it on the city website. I will have to call. I'm in Dallas. We have alkaline soil and water. It seems like our soil is around 7.4. But I will call the city on Monday.

Texas A&M said a plant I sent for diagnosis was chlorotic.

I fertilize with a granular fertilizer about April 1 and again June 1. The amount varies by pot size. After June 1, I kind of leave everything alone until the heat breaks sometime in September. Then I use miracle grow for the rest of the year.

I have perennials in pots that I am concerned about their ph. The annuals, I don't worry about.

I would have thought A&M would have used another word than chlorosis, if they meant something else.


    Bookmark   September 15, 2012 at 8:22PM
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tapla (mid-MI z5b-6a)

It wouldn't be unusual to be doing things right & still have chlorotic plants. My tap-water runs from about 8.5-8.8. depending on the time of year, and I need to acidify or use Sprint 138 to make sure they get the Fe they need - especially in the winter, when I can't flush the containers as copiously.

You prolly want to use citric or sulfuric acid for that many containers (never add water to H2SO4 - add the H2SO4 to water - or just go for the citric acid to be safe). Draw a given amount of fresh water, and add enough acidifying agent to bring the pH down to 5.0-5.5 for most plants, or to your target pH. Make note of how much it took, then, when you water or fertigate, add that much to the same volume of water. Check from time to time to make sure you're on target. If 5.0-5.5 seems lower than you expect, it's because plants do better in container media at about a full number lower than in mineral soils, AND, the pH of freshly drawn water will rise as the dissolved CO2 in it gases off.


    Bookmark   September 15, 2012 at 11:45PM
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nil13(z21 L.A., CA (Mt. Washington))

I would get a better soluble fertilizer with micronutrients instead of the powder. However, I would use the micro I have up first.
Get some pH tape and do what tapla said in order to find out how much of whatever you need to add to get the right pH.
I would still like to know what you pH is. 7ish isn't that bad. Tapla's almost 9 on the other hand, yikes. No wonder you add gypsum instead of dolomite.

    Bookmark   September 16, 2012 at 12:04AM
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I have a lot of family in Dallas. You guys have a pretty high pH (almost 9), but not terrible alkalinity. It wouldn't take a lot of vinegar to fix your problem. I have my uncle add 1 oz of 5% table vinegar per gallon of tap water, and it's worked out great for him. A big jug of distilled white vinegar is just a couple dollars, should last a very long time.

Invest in some pH strips! Cheap and useful.

    Bookmark   September 16, 2012 at 7:31PM
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nil13(z21 L.A., CA (Mt. Washington))

Wow, GT, high pH and low hardness? I didn't know people actually got water like that out of the tap. I guess I am too used to dealing with my liquid rock even if it is only 7.4. Lol

    Bookmark   September 17, 2012 at 11:06AM
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