Switching fertilizers…

[lambo1972]

Hello all! Anybody have any advice or see any problem with switching fertilizers when a plant is in spike? For my Catts and Phals, I’ve been using Jack’s 30-10-10. For my Oncidiums, I’ve been using Repotme Feed Me liquid, which is urea free, but the numbers seem the same. I have a twinkle with 2 spikes and don’t want anything to happen with the spike. Also, I would like them all to be on the same fertilizer as it would probably make life easier. Several folks have told me orchids aren’t big feeders and don’t mind what fertilizer is used. Thank you!

[estación seca]

I agree with the advice that fertilizer doesn't make a lot of difference, if it contains all the nutrients the plants need in appropriate amounts. Sometimes people buy very dilute fertilizers, then dilute them even further. You're not doing this.

[Roberta]

Everything at my house gets the same fertilizer. There are some things that don't get any fertilizer at all in the winter, but not that many (like the Catasetinae that don't even get water in winter) Indeed, orchids are light feeders (with a few excpetions). Think of fertilizer as "vitamins" not "food". They use the minerals to make new tissue (hence the importance of nitrogen) , since they grow slowly they don't need much. THe "food" part (carbs) they take care of themselves, by photosynthesis like all green plants.

[isurus79]

I'll also chime in and say that fertilizer type isn't super important. You only need one fertilizer for all of your orchids and there's no need to have multiple fertilizers for different types of orchids.

[Ray]

Originally Posted by lambo1972

For my Catts and Phals, I’ve been using Jack’s 30-10-10. For my Oncidiums, I’ve been using Repotme Feed Me liquid, which is urea free, but the numbers seem the same.

Maybe I'm reading this wrong, but there is no way a powdered and liquid fertilizer can "have the same numbers".

If I recall correctly, Repotme liquids are Greencare MSU fertilizer dissolved at about 1 pound per gallon, meaning that the liquid is between 1/7 and 1/8 the concentration of the original powder.

[lambo1972]

Thank you all! It was this same orchid that I started a past thread about, my Twinkle ‘Pink Profusion’. The first time it bloomed for me, the flowers never properly opened which was disappointing. Some suggested lack of proper watering but also brought up fertilizer. That’s why I tried the Repotme liquid fertilizer. Someone on orchid board mentioned Calcium and Magnesium which the repotme has listed in its numbers. Jack’s does not. And I read somewhere to use a Urea free fertilizer for Oncidiums. Again, the repotme fertilizer fit this bill as there is no urea, while the Jack’s does have it. The twinkle is again in spike and has 2 spikes. Hopefully the flowers will be better this time. So I guess I should ask, would either of these 2 fertilizers be better than the other? Or is there one I should be using instead? Attached are pics of the 2 fertilizers, Repotme then Jack’s….

[Ray]

Orchids can absorb and use all three forms of nitrogen - nitrate, ammonium, or urea.

The first two are preferentially absorbed through the roots, while the urea is not as well absorbed that way. Conversely, urea is preferentially absorbed by the leaves, while nitrates and ammoniums are less so. Don't get excited about foliar feeding though, as many orchids have waxy cuticle layers on the leaves that makes that a poor uptake pathway.

Nitrates can be absorbed and used as-is. Ammonium compounds are better absorbed when there is free carbon in the roots that can bind with it, and that can be limited. Most fertilizers are a blend of nitrates and ammonium salts.

The bottom line is this: Pick a fertilizer. Feed anywhere from 75 to 125 ppm N weekly. That's it! No need to change for individual plants, seasons, growth stage, etc.

If you divide 8 by the %N in the fertilizer, the result is the teaspoons/gallon for the middle of that range, so you can round for convenience.

That 30-10-10 would be 8/30=0.2667, so 1/4 tsp/gal is fine.

The Repotme liquid (I advise against that one because you're paying a lot for water and for shipping it), at 3.15%N would be 8/3.15= 2.53 tsp/gal, so their tablespoon per gallon recommendation is still pretty good.

[Roberta]

As Ray pointed out, either one is fine. Use up one of them, then use the other. So you won't be needing to buy fertilizer for quite awhile. And don't believe everything you read on the 'net . The "Why" part is important! For those who want to make it complicated, they should be able to articulate the reasons.

[lambo1972]

THANK YOU RAY!!!

Originally Posted by Ray

Orchids can absorb and use all three forms of nitrogen - nitrate, ammonium, or urea.

The first two are preferentially absorbed through the roots, while the urea is not as well absorbed that way. Conversely, urea is preferentially absorbed by the leaves, while nitrates and ammoniums are less so. Don't get excited about foliar feeding though, as many orchids have waxy cuticle layers on the leaves that makes that a poor uptake pathway.

Nitrates can be absorbed and used as-is. Ammonium compounds are better absorbed when there is free carbon in the roots that can bind with it, and that can be limited. Most fertilizers are a blend of nitrates and ammonium salts.

The bottom line is this: Pick a fertilizer. Feed anywhere from 75 to 125 ppm N weekly. That's it! No need to change for individual plants, seasons, growth stage, etc.

If you divide 8 by the %N in the fertilizer, the result is the teaspoons/gallon for the middle of that range, so you can round for convenience.

That 30-10-10 would be 8/30=0.2667, so 1/4 tsp/gal is fine.

The Repotme liquid (I advise against that one because you're paying a lot for water and for shipping it), at 3.15%N would be 8/3.15= 2.53 tsp/gal, so their tablespoon per gallon recommendation is still pretty good.

---------- Post added at 02:07 PM ---------- Previous post was at 02:07 PM ----------

THANK YOU ROBERTA!!!

Originally Posted by Roberta

As Ray pointed out, either one is fine. Use up one of them, then use the other. So you won't be needing to buy fertilizer for quite awhile. And don't believe everything you read on the 'net . The "Why" part is important! For those who want to make it complicated, they should be able to articulate the reasons.

[Girl_With_An_Orchid]

So I am on the hunt for a new fertilizer and this seems like a relevant thread 😅. I’ve been using a miracle gro 20-20-20. I know it’s not the best but I have been stubbornly using it up bc I couldn’t make myself toss it but! It’s almost gone so I need something new! What are people using? I’ve also heard kal-pac being used (or something that sounds like that). Where can I get that? Thanks!