# Leaf tip die back. A sign of too much light?



## mrhappyrotter (Mar 23, 2013)

Short version: 

I've had several Phrag. Jason Fischer x Beauports for almost 10 years, that suffered from constant and severe leaf tip die back. Leaves would turn brown and dry out to the point that entire leaves would die. I've tried many, many remedies under the assumption of issues like too much fertilizer, nutrient imbalance, too little water and too warm of conditions. Nothing worked and I finally gave up last summer and grew them in deep shade. When moved to deep shade, the plants thrived, had almost no die back and even managed to bloom most heavily.

Flash forward to this fall after moving the plants inside. They stay constantly in cooler temps (upper 60's to low 70's). They were receiving standard phrag lighting, and the die back happened again. So, again, out of frustration, I moved them off the light shelves and onto a stand next to the lights and the die back has stopped again.

So, as the title says, is leaf tip die back a symptom of too much light?

Longer version:

Over the years, I've tried lots of different "remedies" assuming a number of different potential causes. I reduced feeding rates, reduced potassium levels, increased watering and took steps to keep the plants from getting too warm. My running theory was that they were not heat tolerant and/or that they were very sensitive to salts or excessive nutrients. Nothing ever worked. The leaves would pretty consistently die back pretty severely. Sometimes, 1/2 a leaf or more would turn brown and dry out over the course of a week or so. I even tried growing these plants indoors year round (where temps never exceeded the mid to upper 70s) and watered with RO or rain water pretty much exclusively.

Then last summer, I gave up entirely. I set the plants outside (in the heat) but in the very shadiest of spots I have. To my surprise, they thrived and even bloomed heavily. The die back ceased almost entirely. At the time, I didn't think it had anything to do with the light, I thought they had perhaps matured enough to out grow the die back.

This fall, I replaced all my lights with T8 fluoros and placed these plants close to the bulbs like all my other phrags. Shortly after, the die back started happening again, despite the moderate temps (upper 60s and low 70s) and reduced feeding regimen.

Once again, I gave up and decided that these plants weren't going to thrive for me, no matter what, so I moved them off the light shelves and onto various stands near the lights, but not directly under them. Then, very noticeably, the leaf tip die back ceased again.

What I don't get is that all this time, the leaves have never showed the typical signs of excessive light. They've always been dark green (as if they weren't receiving enough light).

Obviously, I can't say for sure if this will prove successful in the long term, but for now, in the short term, the leaf tip die back hasn't returned -- and this is the longest period of time with no die back since the summer when they were in deep shade.

Any thoughts? Comments?


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## Eric Muehlbauer (Mar 24, 2013)

I've had way less leaf tip dieback since switching to K-lite. And I fertilize phrags heavily.


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## phraggy (Mar 24, 2013)

I use,as a fertilizer, on my phrags blood and bone meal. Just a teaspoonfull sprinkled on the compost twice per year. I don't get this problem even though they are in fairly bright light-- but no sun. What does for one doesn't do for the other one!!!
Ed


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## mrhappyrotter (Mar 24, 2013)

That's the odd thing, guys. One of the things I tried was very low fertilizing, as in rain or RO with infrequent and very small doses of fertilizer. And since the end of last year, it's been geared more towards low potassium. And yet the plants still suffered from sudden and severe die back.

The only period(s) of time that I've seen absolutely no issues with this specific hybrid are when it was moved to, and grown in low light conditions -- far less than I'd reasonably expect to grow any phrag.

The point being, it seems like the cause may have been too much light (too intense), and yet I never saw any of the typical signs of excessive light levels (i.e. bleached leaves, light colored leaves, sunburn).

Again, still too early for me to conclude that reduced light will eliminate this specific problem in this specific cross, but I'm starting to get hopeful.


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## Rick (Mar 24, 2013)

How are they potted and are you adding some form of calcareous amendment to the mix? Are you using RO/rain water or tap water? Generally LTP is some combination of too much salt (with K and Ca excess typical in orchid culture) without enough water. Have you measured TDS in the pot? I have a 10" pot of Phrag caricinum set up with Leca in a semi hydro arrangement (so always plenty of water). It also was plagued with LTP even though kept right up next to the swamp cooler. LTP was greatly reduced by low k feeding, but when I got my TDS meter I found very high TDS levels in the sump water. Dumped and replaced with RO, measured the next day and high again. I probably repeated this daily for a few weeks before the residual TDS held up in the LECA dropped to low levels. Leaf quality is even better now. But just goes to show how even a supposedly inert potting media can influence pot chemistry well beyond what we know about the chemistry of the water/chemicals we pour into the pot.


Light level comparisons are hard to figure without a meter (for me), but if you have a bunch of other phrags without the problem in higher light levels, the Jason Fishers should be fine right up there with the rest. But if it works for these plants then why fight it? It might be normal for these plants. But it could be a symptom of excess pot salt.


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## gonewild (Mar 24, 2013)

Are all of the leaves having tip burn?
Or is it on only new or old leaves?

Humidity?

When the plants were outside did they get more water than when inside?


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## mrhappyrotter (Mar 24, 2013)

* How are they potted and are you adding some form of calcareous amendment to the mix?

This has changed over the years. The plants have been in fir bark mix, CHC, pure sphag and now a mix that is primarily rockwool for the past few years. For most of these mixes (including the current rockwool mix) I've had either oyster shell, eggshell or some combination of the two as a top dressing.

* Are you using RO/rain water or tap water?

This has also changed quite a bit through the years. I used to water with rain and tap, sometimes pure tap, sometimes pure rain or a combination of the two. But plants always get flushed with pure water (rain, distilled or RO) frequently. 

* Have you measured TDS in the pot?

Yes, with a simple EC meter, but in the 10 years or so of having the plants, TDS would have and could have changed drastically -- it's never correlated to the die back. For instance, when I never let the TDS get above 150, still had die back. 

* Are all of the leaves having tip burn? Or is it on only new or old leaves?

It does normally strike the newest leaf or newest 2 - 3 leaves when it happens. I'd considered the possibility of a nutrient imbalance (though again, this doesn't affect other plants) ... but I've always used a variety of ferts under the assumption that if one brand/formulation is lacking, perhaps another will make up for it. I also frequently use (diluted) fish tank water as sort of a natural supplement -- it's got nitrates and possibly trace nutrients.

* Humidity?

Highly variable and little to no correlation to the die back. I'd say the lowest I've ever seen in the growing area is 45%, normal is 55 - 60% in winter, higher in summer and 80 - 90% after plants are misted (which is a once or twice a day exercise).

* When the plants were outside did they get more water than when inside?

I've always grown them sitting in water (except when I went through the "maybe they like dryer conditions like caudatum types" experiment).

I guess the overall answer to most any cultural question is "it's changed over the years" as my general cultural practices have improved AND as I've experimented with various theories as to what was causing the leaf tip die back on these plants. Certainly, I've experienced some leaf tip die back on other phrags, but never so severely, so suddenly and so consistently as with the JF x BP.


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## gonewild (Mar 24, 2013)

How many plants are showing this?
Are they all siblings from the same cross?
Is this the only cross that has the problem?

If only this one cross is having the issue and it has been on going for years then you can not discount a genetic fault. Some individual plants just have "bad" genes.


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## mrhappyrotter (Mar 24, 2013)

gonewild said:


> How many plants are showing this?
> Are they all siblings from the same cross?
> Is this the only cross that has the problem?
> 
> If only this one cross is having the issue and it has been on going for years then you can not discount a genetic fault. Some individual plants just have "bad" genes.



It's 3 plants, started out with 5. One plant is large has many growths and has bloomed several times through the years. One is smaller, multi growth (only because it's barely stayed ahead of the die back over the years) but has never bloomed. Third one is barely holding on to life and looks more like a 3 seedling compot than a 10 year old plant.

They're all sibs of the same cross. I do get minor leaf tip die back on my other phrags from time to time, but it's usually very minor and never so severe and consistent.

So, yeah I'm convinced that it's just a genetic susceptibility to die back with this particular cross -- just trying to make sense of whether the die back is sometimes a symptom of too much light since it's starting to appear that reducing the light has eliminated the issue.

I suppose it could be that the plants simply don't grow as fast when they're in low light, and thus whatever the primary cause of the problem is, it simply doesn't manifest.


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## gonewild (Mar 24, 2013)

mrhappyrotter said:


> I suppose it could be that the plants simply don't grow as fast when they're in low light, and thus whatever the primary cause of the problem is, it simply doesn't manifest.



Exactly.


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## SlipperKing (Mar 24, 2013)

Its what Rick mentioned above, TDS. I have 20+ Phrags from all types of breeding and I like others was plague by the leaf tip die back until I stopped over fertilizing. Has nothing to do with the growing substrate unless you are harboring too much salt! Mine are in CHC with additives or Orchiata with additives or S/H and there is a gamete of light levels. I'm happy to say none have the dreaded LTD anymore. I use rain water 3-4 times then fertilize at 30-50 PPM of N. They grow and bloom fine. Stop adding fertilizer for the next 2-3 months and watch what happens. Don't be impatient...wait.


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## Leo Schordje (Mar 25, 2013)

SlipperKing said:


> Its what Rick mentioned above, TDS. I have 20+ Phrags from all types of breeding and I like others was plague by the leaf tip die back until I stopped over fertilizing. Has nothing to do with the growing substrate unless you are harboring too much salt! Mine are in CHC with additives or Orchiata with additives or S/H and there is a gamete of light levels. I'm happy to say none have the dreaded LTD anymore. I use rain water 3-4 times then fertilize at 30-50 PPM of N. They grow and bloom fine. Stop adding fertilizer for the next 2-3 months and watch what happens. Don't be impatient...wait.



What Rick said, plus, if I read your posts correctly you are top dressing your potting mix with oysershell, or egg shells. I would try to eliminate them. The oyster shell could very well be the cause of your problem. Too much calcium. If you are using K-Lite now, it has all the calcium the plants need. Majority of Phrags prefer mildly acidic potting mix. The oyster shell takes the pH more toward the alkaline and alters the ability to take up nutrients. 

So my suggestion would be to begin repotting and don't add a top dressing of oyster shell. Keep them moist to wet. Don't let them dry out between watering. They should improve, and be able to grow in higher light without brown leaf tips. But do give them the 2 -3 months no fertilizer rest as Rick suggested, especially after repotting to get rid of oyster shell. 

My thoughts, hope it helps


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## Leo Schordje (Mar 25, 2013)

Phrag exceptions, kovachii and fisherii and perhaps a few others (xeriphyticum?) want a potting mix slight more alkaline than acidic, these are the ones that benefit from oyster shell. 

Phrag extaminodia prefers a more strongly acidic mix, the addition of a small amount of peat moss in the mix, as peat tends to take pH lower than the typical 6.5 that most mixes end up near. I do mean peat, not dried sphagnum.Peat is the crumbly brown stuff that comes in bales, dug out of old bogs, not to be confused with sphagnum moss, which is harvested live, and is dried, then baled then shipped.


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## Rick (Mar 25, 2013)

Leo Schordje said:


> Phrag exceptions, kovachii and fisherii and perhaps a few others (xeriphyticum?) want a potting mix slight more alkaline than acidic, these are the ones that benefit from oyster shell.



If you are using K lite (or MSU pure water) I would avoid the alkaline ammendments for these also.

For one thing the calcareous materials are highly adsorbant of phosphate and with reduced phosphate in K lite, you can end up with very little avialable P in the short term. Also the higher pH from these ammendments reduce the solublilty of phosphate (with calcium, and at pH's lower than you'd suspect). So trying to get that pH in the 5.5 to 6.5 range is optimal for P uptake.

Secondly I've been looking at the alkalinity/nitrate relationship in plants at the enzyme level. It's almost species specific, but the optimal pH for Nitrate Reductase, the enzyme pathway that alows plants to convert nitrate to ammonia for internal use, is generally most efficient at pH's under 7.5 but greater than 6.0 for the species theyve done testing on. It also doesn't like a lot of TDS. 

So if you want to use a high NO3 percentage nitrogen source (like K lite or MSU) then Bill Argo's recomendation for use in a low alkalinity system is the way to go. Keep the pot salts low, don't add (much if any) high alkalinity pot amendments, and water a lot to maintain stable pH.


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## gonewild (Mar 25, 2013)

I would agree with both Ray and Rick except the condition is limited to a few plants in the collection and they are all genetic sibs.

I recall some years back having a couple flasks of Phrags have a similar problem. I don't remember what the cross was but I believe one parent was Beauport. So perhaps Beauport genetics has something to do with it?


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## Rick (Mar 25, 2013)

gonewild said:


> I would agree with both Ray and Rick except the condition is limited to a few plants in the collection and they are all genetic sibs.
> 
> I recall some years back having a couple flasks of Phrags have a similar problem. I don't remember what the cross was but I believe one parent was Beauport. So perhaps Beauport genetics has something to do with it?



It could, but is the Beauport making it more light sensitive of salt sensitive. The two actually go hand in hand from a water uptake standpoint.

What are the species in Beauport BTW?


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## gonewild (Mar 25, 2013)

Rick said:


> It could, but is the Beauport making it more light sensitive of salt sensitive. The two actually go hand in hand from a water uptake standpoint.
> 
> What are the species in Beauport BTW?



Leaf tip damage would be from salt or dehydration (low humidity). 
But the damage seems aggravated by light.(The fact that the damage stopped in low light)

It sounds correct the recommendations you made to offset the problem, but my suggestion is that based on this one cross the entire collection does not need a cultural change.

Beaumont is (caudatum x Mem. Dick Clements) and it should tolerate very strong light with the caudatum parent .... that is why I suggest a genetic fault.


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## Rick (Mar 25, 2013)

gonewild said:


> Leaf tip damage would be from salt or dehydration (low humidity).
> But the damage seems aggravated by light.(The fact that the damage stopped in low light)
> .



But higher light/temps increases water uptake. So dehydration/osmotics could be excaserbated by something trying to uptake a lot more water than normal and not just sunburn sensitivity.

If it otherwise grows and blooms fine in the lower light, then no point in pushing it to brighter, and we just adapt to what the plant wants. But if it won't grow/bloom in the dark, then leaf tip burn is the least of its problems. The assesment of this is inconsistent. In the first post it says they grow and bloom fine with shade. Then later on only one of 3 is good the other 2 are crappy, and 2 others are long gone. So it seems like only one in 5 has done well even when pushed back into darker conditions.

I guess if things are changing from a month to month basis and the plant is always in recovery mode, then its also hard to figure if dark growing is good or not for this plant. I think its a good excuse to get a conductivity meter to see whats going on in the pot.:wink:


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## gonewild (Mar 25, 2013)

Rick said:


> > But higher light/temps increases water uptake. So dehydration/osmotics could be excaserbated by something trying to uptake a lot more water than normal and not just sunburn sensitivity.
> 
> 
> 
> ...


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## Rick (Mar 25, 2013)

gonewild said:


> Rick said:
> 
> 
> > But even if this is the case the genetics of the plants are weak in relation to that environmental condition.
> ...


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## Ozpaph (Mar 25, 2013)

Could his oyster shell be contaminated with sodium etc from salt water?


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## Rick (Mar 25, 2013)

Ozpaph said:


> Could his oyster shell be contaminated with sodium etc from salt water?


 Nothing's impossible, but there's a handful of other things with oyster shell that are a sure bet.


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## Ozpaph (Mar 26, 2013)

Rick said:


> Nothing's impossible, but there's a handful of other things with oyster shell that are a sure bet.



could you elaborate, please?


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## Rick (Mar 26, 2013)

Ozpaph said:


> could you elaborate, please?



Excess bicarbonate/pH increase causing reduction in nitrate utilization, and adsorption/precipitation of phosphate causing phosphorus deficiency (short term with each fresh top dress).


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