Argggggh. . .How many fertilizers do I need???

seaecho1(SW CA)May 20, 2010

Major confusion here. I had about half a dozen different kinds of fertilizer, and realized recently that they are all at least several years old. Started wondering how long they should be expected to last, and Googled it. Sure enough, they were probably all no good! Long story short, I decided to throw them all away and get new. My dilemma: I have over 100 houseplants of all types. Dracaenas to spiders, to cactus & succs to pothos, philos, begonias, shefs, crotons, gesneriads (no AVs), acalyphas, hoya, Boston fern, clivia, anthyrium, orchids, epis and a few stapeliads.

The fertilizers I had were Osmocote, Peter's 20-20-20, orchid bloom booster, Epiphytes Delight, Miracle Gro Houseplant, bone meal, and Gro Mor Orchid growth formula. I did read that Osmocote keeps longer, so I kept it.

My question is, do I need to buy all of these again? Or can I buy just one or two or three types and have it work for all my houseplants? I bought Schultz Plus 10-15-10 the other day, but don't know what else to get. I don't want to spend a fortune just on fertilizer! Thanks!

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penfold2(4b, MN)

Long answer: Fertilizer Program for Containerized Plants

Short answer: Get yourself some Dyna-Gro Foliage Pro 9-3-6 and call it a day. It's the only single fertilizer I know of that contains all essential plant nutrients (including Ca and Mg) in a proper ratio for most plants. I use it on all my plants including succulents, bromeliads, orchids, and other tropicals. Avoid any fertilizer where the middle number is the highest.

    Bookmark   May 20, 2010 at 9:55PM
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pirate_girl(Zone7 NYC)

Come on now, don't keep us in suspense. I've got a varied bunch of fertilizers too, how long are they good for?

If I were you I'd settle for what you just bought &/or buy one more, a balanced fertilizer like 20-20-20 which I'd assume can be used for most everything.

    Bookmark   May 20, 2010 at 10:23PM
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And, for example for C&S, dilute it to 1/4 strength.

    Bookmark   May 20, 2010 at 10:55PM
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tapla (mid-MI z5b-6a)

Fertilizers are good indefinitely, even if they get wet, but it'd difficult to get the solution strength correct if they DO get wet.

ALL plants use nutrients in VERY close to the same ratio. The ratio in which they use nutrients is also reflected in the ratio of nutrients contained in their living tissues (no surprise there). For every 10 parts of N plants use, they use about 1.5 parts of P and 6-7 parts of K. I could walk you through the factoring we need to do because the P and K % on fertilizer packaging are not the actual %s of P and K, they are reported as PO5 and K2O. The actual P is .43 of what's reported and the K is .83 of what's reported.

Anyway, when the math is done, it comes out that fertilizers with a 3:1:2 ratio (24-8-16 MG/Peters, 12-4-8 MG, 9-3-6 Foliage-Pro are all examples) supply nutrients in almost exactly the ratio in which plants use them. This is a considerable advantage because it allows you to fertilize at the lowest levels possible and still not have nutritional deficiencies. This low level of salts in the soil facilitates water uptake, as well as the nutrients dissolved in water.

1:1:1 ratio fertilizers like 20-20-20 supply too little K in relation to N, and 6X more P than the plant can use, in relation to N. This unnecessarily raises the level of salts in the soil and is wasteful/more costly because so much extra P and K need to be supplied to get enough N to the plant.

You might have to go to the net to get it, but Foliage-Pro 9-3-6 is about the best all-purpose houseplant fertilizer out there. It has ALL the essential elements in the correct ratio to each other. It doesn't get any better.

I know we should never say never, so I'll say 'ever' ..... I cannot imagine a scenario where any of us could 'ever' benefit from using a fertilizer for plants in containers with the middle # (P) higher than either the 1st or 3rd #s (N or K). The extra P is a total waste, the plants can't use it, and it causes several issues related to pH and inhibiting uptake of other nutrients (N, Fe, and Mn in particular, but others, too).


    Bookmark   May 21, 2010 at 12:34AM
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seaecho1(SW CA)

I have read online that fertilizers ARE NOT good indefinitely, except for slow release pellets, such as Osmocote. Guess I'll have to go dig them out of the trash if what you say is true, Al. Well, wouldn't ya know I'd get a fertilizer with a higher middle number? Boy, just can't win. Okay, thanks so much for the responses. I'm going to get some Foliage Pro 9-3-6 online and be done with it.

    Bookmark   May 21, 2010 at 12:47AM
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AndrewH(z8 Vanc. WA)

Al, you would recommend Foliage Pro 9-3-6 even for blooming plants: Hoyas, desert cactus, jungle cactus, African violets, etc?

    Bookmark   May 21, 2010 at 7:42PM
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I've got some Miracle Grow 8-7-6 liquid and its about 7 years old and it makes a peace lily bloom which has never been given anything else. It gets a few drops in water about every 3 months.
I do think perhaps depending on storage temperature fertilizer may not last forever if it got frozen or stored at extreme high temps for an extended period of time but I'm no scientist either.

    Bookmark   May 21, 2010 at 8:51PM
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tapla (mid-MI z5b-6a)

Chemical fertilizers are salts and will last as long as salt lasts, which is pretty much forever. Even if they get combined with a small amount of water (condensation), it doesn't change the strength or chemical composition of the mixture, it only changes the phase from a solid to a liquid/suspension. Dry organic fertilizers that are comprised of various mineral elements and 'meals;, like feather/hoof/bone/horn meals will remain effective indefinitely if kept dry because decomposition depends on moisture. The only thing left is liquid organic fertilizers like fish emulsion, which contain bactericides that work to prevent breakdown as long as the number of ppm of the bactericide is high enough, as when the fertilizer remains undiluted. Diluted fish emulsion spoils quickly because the ppm level of the bactericide is not as high as it is in the undiluted product. Freezing has no effect on the chemical composition of any of these products.

Yes, Andrew. I would recommend FP 9-3-6 for blooming plants as well. While there 'could' conceivably be the rare case where P is deficient in (garden/beds) mineral soils, making a high-P formula useful for that specific application, they are generally counter-productive. In containers, the media supplies so little nutrition that we may as well consider it devoid of nutrients. This means plants depend almost solely on the nutrients we supply. Since we KNOW plants use about 6x more N than P during all growth phases, how can we justify using a fertilizer that supplies more P than N? I don't know if I mentioned it upthread, but excessive P in the soil solution unnecessarily raises the level of TDS/EC (makes it harder for plants to absorb water and the nutrients dissolved in water), unnecessarily raises pH (already a significant issue in our long term houseplant plantings), an inhibits the uptake of several nutrients, chief among them being Fe and Mn (iron and manganese), but N as well.

This is a very common scenario: A grower is using 10-15-10 and notices some yellowing of foliage. Thinking the plant is lacking N, he/she fertilizes. The yellowing grows worse and no cause can be determined, so it must need more fertilizer - right? More fertilizer applied - yellowing grows worse ..... and so on.

What's happening: The excess P in the soil is causing an antagonistic deficiency and inhibiting Fe and Mn uptake, which causes chlorosis. Actually, it may also be inhibiting N uptake, which also causes chlorosis. Additionally, because 10-15-10 provides about 9X more P than the plant can/will use, when N is depleted from the soil, there is still a large amount of P. Adding more of the high-P formulation only exacerbates the problem, so it's a never-ending spiral.

This doesn't occur in every case so it's readily noticeable, but it does occur to some degree anytime we use a high-P formulation for containerized plants. There is more than enough P in 3:1:2 ratio fertilizers (examples: 24-8-16, 12-4-8, 9-3-6) to meet the need of any blooming plant. Tip: keep the P levels as low as possible for Hibiscus and never use a high-P formulation. A little extra K is nice for Hibiscus in the form of a little potash mixed into the soil or a little ProTeKt 0-0-3 added to your 3:1:3 ratio fertilizer solution.

It's not an accident that MG and others label their 3:1:2 ratio fertilizers as "All-Purpose" fertilizers. They supply nutrients in the ratio found in plant tissues AND in the ratio in which plants use them. They offer you your best opportunity at keeping your salt levels as low as possible w/o nutritional deficiencies, which is a very good thing. That is a strategy woven into the nutritional supplementation of all commercial growing ops.


    Bookmark   May 21, 2010 at 9:33PM
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AndrewH(z8 Vanc. WA)

Fascinating! Thank you Al.

    Bookmark   May 21, 2010 at 10:48PM
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tapla (mid-MI z5b-6a)

Thanks. I did make a typo, though. In the next to the last paragraph I meant to type "A little extra K is nice for Hibiscus in the form of a little potash mixed into the soil or a little ProTeKt 0-0-3 added to your 3:1: ratio fertilizer solution." Not your 3:1:3 ratio .....


    Bookmark   May 21, 2010 at 11:14PM
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Fascinating is right! Thank you Al for all this information!

It is this information that has made my choice in fertilizer very very easy..

All I use is Foliage Pro, sometimes with Pro Tek, and A bit of Osmocote with minors when I get lazy with the Foliage pro.

This is what I got from just FP on some of my plants...

    Bookmark   May 22, 2010 at 8:02AM
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tapla (mid-MI z5b-6a)

If I can just take a second on SeaEcho's dime to go OT and say I'm always excited to see the fruits of Mike's efforts. He has come such a long way in his abilities as a grower. Good job, Mike - strong work!


    Bookmark   May 22, 2010 at 11:28AM
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Thanks Al for your expertise and helping us to understand how fertilizer's work. I have been using the 9-3-6 since you suggested it to me for my Lisa cane. All my plants are doing great and I know it's because of this. I have fertilizer's for my blooming plants and cactus and succulents but after reading your explanation of how plants don't benefit from the higher middle number, and in the long run it is detrimental to the plant I am getting rid of them and just using the ProFoilage 9-3-6. Also, looking at Mike's pic, especially the blooming ones (beautiful plants Mike) further convinced me to do this. Thanks again Al for stating things in a way that is easy for us to understand, process and apply to our plants!! Ellen

    Bookmark   May 22, 2010 at 2:38PM
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