Does High Number P Fertilizer really work?

[NYCorchidman]

I have read mixed stories, but are there any good articles or study to back it up?

I always thought it was just a marketing gimmick.

The basic knowledge for many is that N is for the leaf and P is for the flower, so the higher number of P equals more ( or better) flowers, which I don't think is how it really works.

Or is it more of the ratio of N to P that bring out results if any at all???

I have always used a balanced fertilizer and things are all well including the flowering department, but I'm just curious as it bothers me every time I online shop and see these "bloom booster" products.

Any good info is appreciated.

[Laserbeak]

From what I've read it's more the ratio that helps induce blooming than the actual high amount of phosphorous.

[Jayfar]

From what I've read in various discussions, it may not be so much the ratio per se, but rather the reduction in Nitrogen.

[Orchid Whisperer]

There was a link to a peer-reviewed scientific article on NPK effects on orchids that I recently came across & posted on another thread: Nitrogen, Phosphorus, and Potassium Requirements for Optimizing Growth and Flowering of the Nobile Dendrobium as a Potted Orchid
The study used nobile dendrobiums, but you can probably extrapolate to many other orchids.

General conclusions (I am simplifying a bit to be brief):
- its important to provide N at certain levels
- it is also important to provide K at certain levels
- P is needed, but not as much as N or K.
- Timing for when plants receive certain nutrients does have an effect on plant performance

Scroll through the article, have a look at Figure 5 first, then read the article for the details. It is not surprising that N and K are the most important macro nutrients to provide for plant performance. This is true for most plants.

[My Green Pets]

My 2005 copy of orchids for dummies () says that it has not been shown to make a difference.

[ALToronto]

I've had plants with stagnant sheaths - the sheath grows to a certain point and then stops for whatever reason, and does nothing for months. In that situation, a couple of waterings with a high P fert can nudge the sheath into developing buds and then flowers.

[NYCorchidman]

Originally Posted by ALToronto

I've had plants with stagnant sheaths - the sheath grows to a certain point and then stops for whatever reason, and does nothing for months. In that situation, a couple of waterings with a high P fert can nudge the sheath into developing buds and then flowers.

Wouldn't it be possible that it was just a coincide unless you have two groups of the same plant and treat them differently??

It is just a course of life for many cattleyas to make sheaths during the summer and fall, then they won't flower until the following spring.
I have one LC that does this for an example. It is just a life cycle that is not affected by fertilizer, but rather by the day length as many catts do use it as a seasonal que.

---------- Post added at 09:22 AM ---------- Previous post was at 09:20 AM ----------

Originally Posted by Orchid Whisperer

There was a link to a peer-reviewed scientific article on NPK effects on orchids that I recently came across & posted on another thread: Nitrogen, Phosphorus, and Potassium Requirements for Optimizing Growth and Flowering of the Nobile Dendrobium as a Potted Orchid
The study used nobile dendrobiums, but you can probably extrapolate to many other orchids.

General conclusions (I am simplifying a bit to be brief):
- its important to provide N at certain levels
- it is also important to provide K at certain levels
- P is needed, but not as much as N or K.
- Timing for when plants receive certain nutrients does have an effect on plant performance

Scroll through the article, have a look at Figure 5 first, then read the article for the details. It is not surprising that N and K are the most important macro nutrients to provide for plant performance. This is true for most plants.

Thank you, but I am already aware of that article and it is mainly for dendrobium nobile hybrids.
I cut ALL fertilizing by July on my nobile hybrids.

[Ray]

There is no doubt that orchids need a lot more nitrogen than other elements, but they don't need a lot.

Feeding an excessive amount of nitrogen will result in emerald green, leggy, flowerless plants. Feeding a small amount is much better.

The whole "Phosphorus is a Bloom Booster" is marketing hype. Search the forums for a more detailed explanation.

[tucker85]

Originally Posted by NYCorchidman

I have always used a balanced fertilizer and things are all well including the flowering department, but I'm just curious as it bothers me every time I online shop and see these "bloom booster" products.

Any good info is appreciated.

First of all, I don't like to try to fix something that isn't broken. Since you say your orchids are doing well, I would keep doing what you've been doing.

Second, a four part study called "Growing the Best Phalaenopsis" reported that bloom booster fertilizers had no effect on the timing or quality of blooming in phals.

http://www.hrt.msu.edu/faculty/Runkl...sis_Part_2.pdf

Third, some bloom type fertilizers say on the label to use it when the plant is blooming. They don't say to use it in order to induce blooming. I think that's because the lower nitrogen is unlikely to interfere with the bloom cycle. Some growers believe that excess nitrogen can interfere with or shorten the blooming cycle although I've never seen any evidence of it. That's only my personal opinion. But again, if you're orchids are doing well, I don't see any reason to change your culture.

[james mickelso]

In uncontrolled trials with stubborn bloomers (mostly catts and laelias) I have gotten good results from changing the ration of N and K. I lessen the N to change the ratio. And I do it when the pbulb is about halfway to maturity. That is usually when the bud primordia is developing. In nature the rainy season brings lots of N from rain (most N is created by lightning) and it is available to the plant at all times. During the dry season there is less rain and the P and K build up in the leaf litter when the rain lessens and doesn't leach it out. Just deduction I know but it works for me for the most part. If I ever get another large gree house and can get duplicate catts/laelias of the same species I will experiment. But I agree if you are having good blooming don't change a thing.