# Yellowing leaves



## PHRAG (Feb 27, 2007)

I have this problem. It has happened to phals, a couple of neofinetia, one or two miniatures and a couple of other species. It is not a pest issue that I can see. 

This is what happens. Leaves, usually the oldest leaves on the plant, begin turning yellow and eventually fall off. It happens one leaf at a time. In a couple of plants, the leaves have all fallen off, one at a time. Humidity and temperature are not any higher than usual, and I actually cut back on the amount of time I leave my lights on because I think maybe my plants are getting too much light. Some were looking very pale, but now they are greening back up again. I don't think it is crown rot, because the plants actually stay alive. Some just lose one or two leaves, and in a couple of cases I lost the whole plant but the roots were still healthy. Very odd indeed.

Any ideas?


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## gonewild (Feb 27, 2007)

PHRAG said:


> I have this problem. It has happened to phals, a couple of neofinetia, one or two miniatures and a couple of other species. It is not a pest issue that I can see.
> 
> This is what happens. Leaves, usually the oldest leaves on the plant, begin turning yellow and eventually fall off. It happens one leaf at a time. In a couple of plants, the leaves have all fallen off, one at a time. Humidity and temperature are not any higher than usual, and I actually cut back on the amount of time I leave my lights on because I think maybe my plants are getting too much light. Some were looking very pale, but now they are greening back up again. I don't think it is crown rot, because the plants actually stay alive. Some just lose one or two leaves, and in a couple of cases I lost the whole plant but the roots were still healthy. Very odd indeed.
> 
> Any ideas?



Air pollution?
Can you post photos?


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## PHRAG (Feb 27, 2007)

Lance, I will post photos next time it happens. Right now, none of the plants are losing a leaf. It happens pretty quickly. The leaf turns yellow and within three days falls off completely. No other signs of disease, and the plant usually keeps on growing just fine. I would think it was just old growth dying off, except for the two plants that didn't make it.


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## gonewild (Feb 27, 2007)

Are you fertilizing your plants?


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## PHRAG (Feb 27, 2007)

Not as regularly as I should be. I am, and in low doses, but not every time.


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## gonewild (Feb 27, 2007)

So without nutrients how is the plant supposed to keep it's leaves green and healthy?

Believe it or not plants can starve to death. oke:


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## PHRAG (Feb 27, 2007)

Point taken. But are you sure it couldn't be aliens or something?  

I guess I need to start taking better care with my fertilizing regime.


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## gonewild (Feb 27, 2007)

PHRAG said:


> Point taken. But are you sure it couldn't be aliens or something?



UGH, you do cover your plants with aluminium foil at night don't you?



> I guess I need to start taking better care with my fertilizing regime.



You get an A+ for that guess.


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## dave b (Feb 27, 2007)

The Feb issue of Orchids has an article (part 2) about Phals. In it is a brief talk about the use of potassium and effects of lack of. Seven phals were used in test, given potassium levels ranging from 0 to 500ppm. Interestingly enough, the phal at 50 ppm dosage shows definite yellowing of older leaves. The Phal at 0ppm dosage appears dead, with practically all leaves gone (one severely shriveled leaf left). They quote that all plants suffering potassium deficiency over time died. The other Phals exhibit healthy looking growth, full green leaves, with good blooms. Optimum potassium levels were listed at 200 -300 ppm. Research was conducted at Texas A and M. What i cant find, though i read it recently, is how the ppm dosage corresponds to guaranteed analysis: by wt. that we commonly see posted on our fertilizers.

I too have seen some yellowing, especially on a couple Phals. I have been fertilizing pretty light for a while, and am upping it a bit on these plants.


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## Rick (Feb 28, 2007)

Also when was the lat time you repotted? I grow almost all my phals mounted so I don't generally see this problem, but a bunch of phal growers near me often atribute stuff like this to sour old mix and chlorine in the irrigation water.

Dave sounds like he has some good info too.

You can't get 200 ppm of K out of any natural waters, that will require fertilization. But the ability to extract minerals from the environment is often pH dependent. Often those old acid mixes promote too much uptake of trace metals and nutrients.

There's lots of variables. Also I often get yellowing and leaf loss when humidity is low (rather than high). Reducing light is probably a good try too.


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