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Yellowing leaves with rusty brown spots. Advice?

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Maxijazz View Drop Down
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  Quote Maxijazz Quote  Post ReplyReply Direct Link To This Post Topic: Yellowing leaves with rusty brown spots. Advice?
    Posted: 06 December 2009 at 14:11
 
The rusty brown spots started appearing at the first pair of leaves (the ones with one leaflet), at first i didn't think much of it, and now those two leaves have turned completely yellow. This is the most recent picture taken of another one of the leaves, the pair one level above it, the pair with three leaflets. I've read through most articles on the forum about Magnesium deficiency, cause that's what i suspect the problem is. Most suggest Epsom salts, and i am going to look for it first thing tomorrow. Unless it is caused by something else?
 
The reason for me suspecting the problem being Mg deficiency, is that i've just realized the fertilizer i am using - MiracleGro all purpose plant food, has most of the trace elements such as Zn, Fe, and Mn, though in very small amounts (i assume that's all they need to grow well?), but there's no Mg or Ca in it! This means that if they were using any Mg or Ca it had to come from the worm compost in the initial soil mix, i would assume it isn't enough?
 
If i can't find epsom salts, are there any other ways to boost up Mg and Ca levels?
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Maxijazz View Drop Down
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  Quote Maxijazz Quote  Post ReplyReply Direct Link To This Post Posted: 06 December 2009 at 14:19
Sorry, had problems uploading the pic, this is the .gif file
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sarah louise View Drop Down
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  Quote sarah louise Quote  Post ReplyReply Direct Link To This Post Posted: 07 December 2009 at 01:05
Frankly, it doesn't look like Mg deficiency to me (eg. yellowing leaves with green veins), but I really can't really say much about an image of a single leaf... the spots might just be burn from fertiliser splashing the leaves when you water.

We really need to see pictures of the whole plant in order to assess the damage in context of the overall health of the plant.

If you can't get the images small enough to post them to the thread, larger sized images can be uploaded to the gallery.

To make sure you have enough Ca and MG in your soil mixes add a small handful of dolomite lime before planting (or potting up) and mix well. It will also help keep your pH stable.


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Maxijazz View Drop Down
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  Quote Maxijazz Quote  Post ReplyReply Direct Link To This Post Posted: 07 December 2009 at 14:34
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  Quote Maxijazz Quote  Post ReplyReply Direct Link To This Post Posted: 07 December 2009 at 14:50
The leaves come from this plant, from above it looks just fine.
As you can see in this next pic, some of the higher leaves are starting to lose its color.
Sara thx for your input, hope these pics can help you identify the prob..
I was thinking, maybe they became yellow cause the lowest leaves are now too far from the HID light? If so, it shouldn't develop brown spots, right?
 
I went looking for epsom salts, couldn't find them here.
I got Garden Lime instead. The instruction says it is used to stabilize ph levels and to add magnesium and calcium. The particles are white and really fine. I was wondering, would it be ok to mix it with along with the watering?
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  Quote sarah louise Quote  Post ReplyReply Direct Link To This Post Posted: 08 December 2009 at 01:08
Thanks for uploading more images, if you save them as jpg rather than gif images they will show a lot more detail.

From the pictures it doesn't look to me like there is much wrong with your plant. Lower leaves will yellow evenly and die off naturally as the plant grows. If the yellowing really starts to spread up to higher parts of the plant then they need some extra nitrogen.

There are a lot of things that can cause spotting, as I mentioned earlier, splashing lower leaves with fertiliser will leave small burns as will misting a plant that is under high intensity lighting. Unless the spotting is spreading, or is associated with other symptoms, I'm inclined to think it is just splash burn.

From the little I can see of them, the pots don't look to be very big. If your plants have been in the same pots for a long time it may be that they don't have enough room and are becoming root bound. Plants that are root bound will begin to yellow and look a bit sad and droopy, if you can see a lot of roots coming out of the drain holes you need to replant them into bigger pots with fresh soil.

If they need potting up you can add an extra teaspoon of lime per litre of soil and mix well. If they don't need potting up it would be better to sprinkle a little lime onto the surface of the soil an then water. Garden quality lime doesn't usually disolve fully, so if you mix it with water before applying you run the risk of leaving alot of it in the bottom of the watering can.
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  Quote Maxijazz Quote  Post ReplyReply Direct Link To This Post Posted: 08 December 2009 at 02:27
There's something wrong with my pc, i used to be able to upload .jpeg files but now it doesn't recognize any other files but .gif!!

The plants look healthy overall but i'm just worried about the yellowing leaves and brown spots cause after much reading i realize it might be caused by Mg deficiency. The book that I've been depending on since last year mentioned that Mg deficiency diminishes flower harvest, n thats the last thing i want.

I've had a previous experience where a healthy looking plant initially started yellowing from the bottom, and within a week it became 100% yellow, wilted and die, despite all my efforts to save it.

I'm using 3 gallon pots for them now, and they are 35 days old as of today. I'll definitely lift the pots up today n check if the roots are growing out of the holes at the bottom. Wouldn't 3 gallon pots be big enough for plants that are about 2-3 months old? I'd hate to have to transplant all 5 females, its just so much work! But i'd do what i have to if its a necessity.

If i am re-potting, i'll be sure to add garden lime into the soil mix. Yeah I've realized that it doesn't dissolve well in water. So before i watered them i made sure that it was first in a bottle, i shake it well, then pour it into the watering can, and immediately start watering the plant after that. O well, sprinkling some at the soil surface sounds more efficient!
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  Quote sarah louise Quote  Post ReplyReply Direct Link To This Post Posted: 08 December 2009 at 08:28
Mg deficiency gives the leaf a distinctly stripey look, yellow but the veins stay green. The last pic shows ever so slightly lighter green between the veins but the earlier ones are a more even yellow which to me suggests normal leaf recycling rather than a Mg problem.

 
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  Quote Maxijazz Quote  Post ReplyReply Direct Link To This Post Posted: 08 December 2009 at 15:58
Ok, i've checked the holes at the bottom of the pots and i can see the roots, does this mean they are already 'pot-bounded'?

The average height for my 5 plants are around 32 inches, some have said that the rule of thumb is 12 inch per gallon? So i think its about time to transplant them into bigger pots. I've been lowering the daylight hours day by day, tomorrow they will be receiving 13/11, and day after that will be their first 12/12 day. Will it be a sufficient pot size if i moved them into 5 gallon pots? They will probably finish flowering at about 60 days from now? FYI, they are afghani #1.
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  Quote sarah louise Quote  Post ReplyReply Direct Link To This Post Posted: 08 December 2009 at 22:48
It does sound like they are ready for bigger pots with some new soil. When you change pots don't try and break the root ball open or try and tease the roots apart. Many people do this with root bound house plants but cannabis does not like it at all.

Changing the lighting by an hour a day is unnecessary and does not achieve anything apart from slowing down the start of flowering. It would have been simpler to leave them at 18/6 (or whatever you used during vegetative growth) and made the change to 12/12 in one go.

Normally it's better to leave a plant for a week or so to settle into the new pot before changing over to flowering. In this instance your Afghanis are already experiencing long enough nights to trigger flowering so just keep doing what you are doing with the lighting.

Best of luck with flowering,

sara%3c3ceed%3c20leaf
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