Which nutrients?

sven556(z5 Kansas)August 29, 2013

Ok, so I screwed up and ordered the GH floragro thinking that's all I needed to grow leafy vegetables and herbs (namely lettuce, spinach, basil, and cilantro). It turns out I need the flora-micro to add micro-nutrients.

It looks like I need to get some more nutes! I could just order the flora-micro but I noticed the GH maxigro looks to be an all in one dry nute mix at roughly the same price. Will I see any difference between the two?

Also, I plan on keeping the lettuce in one dwc and the spinach and herbs in another as I believe the later like a higher nutrient concentration. What would you recommend for the concentrations? Or, do I just need to change the solution more often for the spinach?

Thanks for getting me started!

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PupillaCharites(FL 9a)

Last time I looked at those three part formulas, I thought you needed all three (you don't have bloom). They are very generalized formulas. I'd be wary about premixed calcium in that MaxiGro. It's hard to say - the guaranteed analysis and directions are incomplete and vague.

To get an idea for generic nutrient strength, just look at a chart like this, at the EC column, since it is how to rank the preferred relative strength of the generic nutrient solution

EC Values

    Bookmark   August 30, 2013 at 2:43AM
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GH might tell you to buy all three because they want your money, but you don't need Bloom for growing lettuce, and you don't need Grow for growing flowering/fruiting plants. You can get just about whatever NPK numbers you want by adjusting the proportions of each nute. But if you buy an all-in-one, you are stuck with one NPK proportion. That's not to say it won't work, but there just isn't any room for adjusting the formula.

    Bookmark   August 30, 2013 at 12:19PM
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PupillaCharites(FL 9a)

(EDITED and reposted below with suggestions for mix proportions)

This post was edited by PupillaCharites on Sat, Aug 31, 13 at 13:55

    Bookmark   August 30, 2013 at 7:06PM
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PupillaCharites(FL 9a)

OK, I played with Flora Gro and Flora Micro together, if you only use the two parts, and per gallon what is about right:

9 mL Gro
4 mL Micro
comment: Severly Lacking Phosphorus no matter what, deficient in Iron and Boron

17 mL Gro
6 mL Micro
comment: Greatly Lacking Phosphorus no matter what, deficient in Iron

Conclusion: Either get Bloom too, or just go with the MaxiGro - a better (much!) option than the gro/micro parts only
Maxigro 4.5 g per gallon for lettuce
9 g/gallon for spinach

Still, Maxigro meets NPK very well (rather high in ammonia though), except the iron is shortchanged. This is not a problem for the lettuce due to the low requirements and adaptability and final composition of the leaf of 12 ppm iron. But Spinach is less forgiving and has fresh leaf composition of ~28 ppm iron. You probably can get around the iron problem when the plants are starting to get bigger by making weekly nutrient changes, but the phosphorus problem using the Gro/Micro alone will make your spinach grow slow and maybe with a slight tint of purple leaves.

    Bookmark   August 31, 2013 at 1:57PM
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sven556(z5 Kansas)

If I use the maxigro can I add additional iron using liquid chelated iron? I've seen bottles of that stuff at the local greenhouse. What does high ammonia cause?

    Bookmark   August 31, 2013 at 2:55PM
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sven556(z5 Kansas)

on the other hand. If I don't stick with the flora or maxi series; what nutrients would fit my needs the best?

    Bookmark   August 31, 2013 at 2:58PM
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PupillaCharites(FL 9a)


I think you had it right whether you knew it or not the first time. Screwed up and bought just the Flora Grow. If you could do it over again and you were just going for spinach & lettuce the Maxigro plus chelated iron would be a great combination for success. The is no reason to mess with that three part formula at all if all you want to deal with are these. Just what Cole said, if you decide to do anything fruiting stuff, then you can use the Flora 3-part better to shadow the plants changing nutritional needs.

But it is not better for spinach and lettuce. As a matter of fact it is just more money for nothing there.

Don't worry about the ammonia being a problem, it is actually good for you as a beginner since it will help keep the pH a little better. I didn't mean to imply it was a problem, I only mentioned it because you definitely don't want to add anything else with more ammoni*, that's all.

So if I were to recommend, it would be get the MaxiGro and pick up the chelated iron. If you are motivated, add 1.5 ppm of Fe (in chelate form) to your lettuce (optional addition for lettuce, but likely to help) formula or 4 ppm to your spinach formula (you want this). The mix instruction ought to be on the bottle. If you have any doubt, just post in this thread when you get the bottle.

Hey, Popeye's spinach didn't get all that iron out of a lettuce formula ;-)

The only other thing is be careful mixing that maxigro, following whatever their instructions are that everything is really well dissolved and you don't lose any important nutes in any sediment you can easily miss.

Good luck

Note: Regarding the iron 4 ppm addition for spinach. There is a lot of leeway in this and and it would be good to experment. For example with young small plants, probably a 1-2 ppm addition would be just fine, and if you had other higher strength greens in there too, maybe just to make everyone happy, add 3 ppm instead of 4 ppm and the Spinach might not know the difference. If you didn't use the added chelate, the Spinach would still grow, but it would not give give optimal results. More frequent changing of the nutes would help a lot if you didn't add iron. Another thing to consider is Calcium. If you are using water high in Calcium like many everything else is perfect, but if you decide to use pure water like reverse osmosis or rainwater, MaxiGro will nearing to the point of low calcium when used weakly (for lettuce). If that is what you wanted to do for the lettuce, you might need a product called Cal-Mag or Cal-Mag Plus.

This post was edited by PupillaCharites on Sun, Sep 1, 13 at 14:40

    Bookmark   August 31, 2013 at 5:22PM
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sven556(z5 Kansas)

ok, I finely received a bag of maxigro and some chelated iron. I have the two tubs up and running and plants have been in a weak solution of flora gro for about two weeks now. I'm planning on switching over the maxigro tomorrow and working up to full strength over the next week. The bag says to use 1-2 teaspoons per gallon. Am I on the right track thinking 1 teaspoon per gallon for lettuce and 1.5 teaspoon per gallon for spinach?

Can someone please verify my calculations for 4 ppm iron in a gallon of water? 4 ppm is 0.003995436 g/liter or roughly 0.003995436 g/quart. This equals 0.015981744 g/gallon. The iron I have is 11% so 0.015981744 / .11 = 0.1452885818181818 g/gallon. If this is correct I need 0.9443757818181818 g for my 6.5 gallon reservoir or basically 1 gram.

Is there a good way to measure this without a scale? I'm thinking 1/8 or 1/4 teaspoon, which is a unit of volume while grams is a unit of mass. I'm trying to keep this simple. Is it going to harm anything if I put 1/4 teaspoon in each reservoir? It will be way above 4 ppm but the container of iron I have will still last forever at that rate.

    Bookmark   September 12, 2013 at 11:12PM
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PupillaCharites(FL 9a)

Sven, for mature lettuce it is actually 6 grams Maxigro pero gallon of water (29.8 g/5 gal). For small young lettuce plants, use 4.5 to 5 grams/gal.

You really need a scale because the bulk density of the powders can vary when it is pressed and you have to be careful to use the level spoon as a reference. Here is a $10 solution for what you are looking at.


4ppm is the max addition for spinach over what's in the maxigro.

Your calculation is fine, lettuce is max addn of 2ppm, but not as necessary.

Maxigrow density is 2.2 g/ml if you want to be a chef instead of tech; 88% iron chelate edta powder is 0.9 g/ml, not compressed but rather freely poured. A true teaspoon is 5 ml when level. One trick if you want one ml of your chelate powder by gross estimate, is to take a level tsp and divide it into five equal piles and take one or adjust it accordingly. I got 0.90 g twhich would be exactly 1 ml, to you 0.94. Just remember though, these can really really pick up water when exposed to air, so keep airtight except for brief times you need to use them and minimize disturbing them. Make a stock solution by approx 19 to 1 tsp/tsp with *distilled water (walmart or mid fall direct rain)* if you want on the chelate. That way for you each tsp of the solution adds one ppm to your particular res. must keep that stock solution in complete darkness, cool place is good too.

    Bookmark   September 17, 2013 at 3:05AM
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PupillaCharites(FL 9a)

9 g/gal maxigro for spinach (young 6/gal). watch out, maxigro is dense see above, and in the big scheme of things spinich is just a medium strength feeder and lettuce lite. get the scale!

    Bookmark   September 17, 2013 at 3:21AM
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sven556(z5 Kansas)

Thanks for all the info. I changed the solution and added some iron last Friday. Everything seems to be doing great. It wasn't very scientific or precise. I used 1 tsp per gallon for the lettuce and 1.5 tsp for the spinach. I diluted a rounded 1/4 tsp of iron in water and added roughly 1/3 of that to the lettuce and 2/3 to the spinach. By my rough calculations this gives me between 2-3 ppm and 4-5 ppm for the spinach.

I'll try to get a scale soon.

    Bookmark   September 18, 2013 at 9:12PM
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PupillaCharites(FL 9a)

Glad to hear that. Sounds on the strong side though. Just in case watch for accumulation of nutrients. Not saying it will happen given te uncertainty of your measurements, but just defensive driving, in that if you've added too much between estimates and stronger solutions than necessary, you could get a sudden bad reaction and when using a fertilizer like this one since it is especially high in ammonium nitrogen, your solution is over 40 ppm N from ammonium now if I'm remembering right; ammonia toxicity is an example of something that can suddenly happen.

I would use around 9 ppm of iron as the danger limit of spinach and shoot for about 6 ppm in solution as the optimal limit for mature plants including the fertilizer. It is an interval you are shooting for and too little may produce less nutritious veggies or growing deficiencies, but too much can be toxic... Some nutes are flexible but others are less so.

Good luck on getting a calibrated scale (I'm 2 for 2). The scale takes all the guesswork out of this, so if anything ever goes wrong you can troubleshoot much more easily

    Bookmark   September 18, 2013 at 10:55PM
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Not to crap on GH...but unless you buy the Organic General Hydroponics line its all synthetic nutes. When you are ready to see some dramatic results Try Earth Juice Organics.....I have tried them all blown a ton of cash over the years learning the hard way..Today I just use Earth Juice Organics and make Compost tea when I get bored. One other note for growers using a bloom product no need to buy High Brix products save the cash and use Plantation Molasses from Wally World.... Good luck

    Bookmark   September 24, 2013 at 2:40PM
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