Purple leaves: Cold damage, Insect stress, too much light, magnesium or phosphorous

[K-Sci]

Originally Posted by Ray

But, as has been driven home by several truly knowledgeable folks, tissue analysis tells you what the plant has been getting, and nothing at all about what it needs.

I agree. What we can conclude from tissue studies is that the elements in the tissues must be available from water, fertilizer, or the media (i.e. plants don't do fission or fusion).

As far as fertilizers are concerned, to my mind, there cannot possibly be an “ideal formula”, as nutrient demands are quite variable.

I completely agree here too.

I cannot speak for others, but K-Lite’s formula was not based upon tissue analysis at all.

You bring it up often in discussions of K-Lite and plant nutrition. That's the reason I expressed doubt that tissue analysis tells us much of any use.

The role of accumulating potassium was ... further backed-up by chemical analyses of the initial rainfall reaching epiphytes in tropical rainforests.

This tells us that these epiphytes can survive and reproduce successfully in nature with very low levels of N/P/K/Ca/Mg/etc. It does not tell us that these low levels are best for greenhouse or home culture. I suspect you will agree that most orchids grow bigger, faster, and flower more profusely with nutrient levels far higher than in the rain forests. If so, the questions become:

1. What levels of the other nutrients must accompany the higher levels of nitrogen to prevent vitality from being limited by these other nutrients.
2. What levels of these other nutrients are to some extent toxic.

These two levels, sufficient and toxic, appear to allow for a very wide range of the nutrients to be beneficial in greenhouse and home culture. People are successful using ratios such as 10-10-10 and even with bloom boosters that are as P-rich as 10-52-10.

Based upon that info, a lot of folks started experimenting, and in about 2 weeks, we’ll reach the ten-year point in that experiment, and I’ve yet to hear any reports of issues that can be attributed to the fertilizer formula.

That may be, but isn't it also fair to say that the much higher levels of P and K widely used by commercial greenhouses for many more decades have not resulted in issues that can be attributed to those fertilizer formulas. The only one I can think of is the expense of using unnecessary nutrients.

For what it's worth, I've seen far more evidence than I need to very confidently conclude that KelpMax promotes strong root growth and that used as directed it is very beneficial to orchid growth. I am also confident that the higher levels of Ca and Mg in K-Lite are beneficial, if not essential, to good culture for people like me using water with low levels of these elements. This is because I've seen the symptoms of the resulting deficiency.

On the need for added Ca and Mg and the benefits of KelpMax I have no doubt whatsoever.

On the other hand, I see no evidence that using K-Lite produces noteworthy benefits to orchid growth beyond those from the added Ca and Mg. In fact, I also do not recall seeing you claim that any such benefits have been shown. As a result I've concluded that the very low levels of P and K in K-lite are at best an unnecessary risk compared to more conventional fertilizers, such as MSU.

For the forgoing reasons, I've stopped using K-Lite. Just as shadeflower has observed, after using it my orchids came to exhibit purple color that I have not seen kin the past. I have not concluded that the purple color indicates a nutrient deficiency, but there is a study on vanda where purple color and other undesirable symptoms were caused by very low P or K (I'm not recalling which). I'm not saying that K-Lite causes any problems whatsoever, but it is an outlier in P and K levels with no evidence I'm aware of that this benefits the plants. I will also acknowledge that I'm by no means an expert on this topic and that my conclusions may be the result of my ignorance on the subject.

-Keith

[Ray]

Originally Posted by K-Sci

I suspect you will agree that most orchids grow bigger, faster, and flower more profusely with nutrient levels far higher than in the rain forests.

Absolutely. I think that's the difference between a subsistence diet and a healthy one. But...again, it says nothing about the ratios.

These two levels, sufficient and toxic, appear to allow for a very wide range of the nutrients to be beneficial in greenhouse and home culture. People are successful using ratios such as 10-10-10 and even with bloom boosters that are as P-rich as 10-52-10.

Unfortunately, we know little about the true uptake dynamics, which is bound to have an impact. I just recently read an article from some college extension service that talked about how calcium, magnesium and potassium are taken up in an uncontrolled fashion if they are in solution, how they can compete for "capture sites" (my term) within the plant, and how overdoing any of them can cause issues due to the "blocking" interference they can cause. That is, too much of any of them can result in a deficiency in the others.

Phosphorus is a whole different case however, as the plant will take up as much as it can get, whether it needs it or not.

That may be, but isn't it also fair to say that the much higher levels of P and K widely used by commercial greenhouses for many more decades have not resulted in issues that can be attributed to those fertilizer formulas. The only one I can think of is the expense of using unnecessary nutrients.

I think we have to consider that most commercial nurseries don't actually keep plants around for very long, precluding the potential issues, and the breeding stock plants they do grow long-term get repotted regularly, thereby dumping the accumulated minerals in the medium.

Cool discussion - Happy Thanksgiving!

[K-Sci]

Originally Posted by Ray

I think we have to consider that most commercial nurseries don't actually keep plants around for very long, precluding the potential issues, and the breeding stock plants they do grow long-term get repotted regularly, thereby dumping the accumulated minerals in the medium.

Cool discussion - Happy Thanksgiving!

I think there are three types of commercial greenhouses. Those that buy established plants for resale (there are a lot of these now), those who grow orchids from seed then sell them to greenhouses of the first type, and finally, cut flower growers. There are many fewer of the latter than there used to be, but they would be on the front line when it comes to fertilizer ratio selections.

I agree, this is a very interesting discussion. Shadeflower's research kicked off this thread with a lot of studies and evidence I've found to be very enlightening. Some of his statements along the same lines have, in the past, received a cool reception and I was among those who questioned some things he said. Over time, I've come to see that there is vastly more hard data behind those statements than I initially realized. The studies he provided support some very interesting conclusions that run very contrary the conventional wisdom.

-Keith

[thefish1337]

I think a component of the discussion that is being missed is the microbial populations in different people's orchids. Specifically the phosphate and potassium solubilizing bacteria associated with their orchids- if you lack theses functions in the microbial populations that live in and on your orchid roots then you are forced to overcompensate with increased additions of these nutrients.

Applying phosphorous as a salt and without appropriate microbial helpers means that your plant really only takes up phosphorous when it is in its ionic form in solution... the massive increase in concentration that occurs as evaporation and dry down cycles happen causes the phosphorous to be complexed with cationic species which become much harder for your orchid to take up. In a natural system there is a balance between phosphorous immobilization and mineralization/solubilization that dictates the availability of ionic phosphorous. Increasing phosphorous fertilizer without the appropriate microbiology just drives your orchid and media towards immobilization. Additionally, the organic forms of phosphorous that are contained in micro life are an important source of phosphorous as these organisms growth and death releases these organic forms which are less likely to form insoluble complexes. In systems with low organic matter (like most orchid mixes) the deleterious effects of excess salts on microbial populations are much more pronounced. If you combine this with the over use of synthetic pesticides which are harmful to nutrient cycling organisms and it becomes no surprise to me that people start compensating with higher feed rates. There is nothing wrong with this... other than you lose a lot of resilience and efficiency in your growing system.

You can meticulously balance nutrient ratios, or you can use microbes and be lazy but that's just my $0.02. I'd rather use less salts and preserve and promote the functional organisms I've inoculated into my orchids.

[K-Sci]

Originally Posted by thefish1337

You can meticulously balance nutrient ratios, or you can use microbes and be lazy but that's just my $0.02. I'd rather use less salts and preserve and promote the functional organisms I've inoculated into my orchids.

How are you doing this?

-Keith

[thefish1337]

Originally Posted by K-Sci

How are you doing this?

-Keith

There are a number of plant inoculants I have tested, all work pretty well, some better than others. Bacillus subtilis, bacillus amyloliquifasciens, bacillus licheniformis and bacillus pumilus are primarily used in these products. They promote phosphate solubilization through many mechanisms. Ultimately the efficacy of these products comes down to the specific strains of bacteria they use: Bacillus subtilis from product a may not do the same things as Bacillus subtilis in product b. You may find that one product works better in your conditions and growing environment.

1. Tribus Original - 3 species consortium of Bacillus in high concentrations ...200x more concentrated than Quantum Total. I have tested this product for only 6 months but I have seen great results with all my houseplants and orchids.

2. Inocucor - only contains Bacillus subtillis but also is a consortium of beneficial yeasts, lactobacillus and molds. I have used this product for 4 years with excellent results.

3. Quantum Total - contains more species of bacillus + photosynthetic bacteria + humic acid. I have tested this for about 2 years and it works pretty well.

[K-Sci]

Originally Posted by thefish1337

There are a number of plant inoculants I have tested, all work pretty well, some better than others...

1. Tribus Original...

2. Inocucor...

3. Quantum ...

This is interesting. I started using Quantum a couple months after reading Ray's testimony to its effectiveness on OB. Initially I thought the smell might kill me, but I quickly found that the sulfur smell doesn't linger after use and the smell of the product still in the container moderates as the hydrogen sulfide dissipates.

I started using Quantum hoping that lightening can strike twice, with Ray's KelpMax being a very effective product and the first metaphorical lightening strike. The problem I'm having assessing the effectiveness of Quantum is that I lack a means to gauge its effectiveness. What results have you seen that led you to conclude that Quantum delivers on its promise.

-Keith