# sanderianum marks on the leaves



## Elite Orchids (Jun 4, 2019)

i grow my sanderianums in quite bright, but a couple of them have developed marks on the leaves like this - any idea what causes this and what the rememdy is? thanks


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## troy (Jun 4, 2019)

It looks like sinensis, the plant is using the energy from the old leaves, transfering to the new growth is ok, I'd give them some magnesium sulfate, I alternate weekly a low k fertilizer 15-5-15 cal/mag with a 16-16-16 acididic balanced fertilizer used 1/4 teaspoon per gallon of ro with perfect results


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## Elite Orchids (Jun 4, 2019)

troy said:


> It looks like sinensis, the plant is using the energy from the old leaves, transfering to the new growth is ok, I'd give them some magnesium sulfate, I alternate weekly a low k fertilizer 15-5-15 cal/mag with a 16-16-16 acididic balanced fertilizer used 1/4 teaspoon per gallon of ro with perfect results


thank you - much appreciated - i will try


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## Ozpaph (Jun 4, 2019)

looks like its natural.
Unlikely to be 'mites' - wipe the underside of that leaf with a white tissue and magnify.


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## emydura (Jun 5, 2019)

Ozpaph said:


> looks like its natural.
> Unlikely to be 'mites' - wipe the underside of that leaf with a white tissue and magnify.



I agree. I'm not sure what the problem is. The leaves do seem to be getting smaller though, which is not a good sign.


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## Elite Orchids (Jun 5, 2019)

Ozpaph said:


> looks like its natural.
> Unlikely to be 'mites' - wipe the underside of that leaf with a white tissue and magnify.


 - yes - nothing on the tissue paper.


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## Silverwhisp (Jun 5, 2019)

troy said:


> It looks like sinensis, the plant is using the energy from the old leaves, transfering to the new growth is ok, I'd give them some magnesium sulfate, I alternate weekly a low k fertilizer 15-5-15 cal/mag with a 16-16-16 acididic balanced fertilizer used 1/4 teaspoon per gallon of ro with perfect results




Aka “senescence” .


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## Ozpaph (Jun 5, 2019)

I would check the roots.


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## Stone (Jun 5, 2019)

Ozpaph said:


> I would check the roots.


Yes agreed. This is very easy to diagnose. The plant lost roots at some point in the past (12 months?) You can clearly see that because of the smaller new leaves. It is using it's reserves to stay alive and if no new roots come soon - big problems. The oldest leaves are always the first sacrificed for N - mainly - and lack of N is often accompanied by colouring.
No point fertilizing the medium if there are no roots. Maybe a mist once a week with urea will keep the N up. otherwise, I have found with orchids in this state it helps to spray/water with very diluted auxins to get a root going. It's always a long way back though.


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## Elite Orchids (Jun 6, 2019)

Stone said:


> Yes agreed. This is very easy to diagnose. The plant lost roots at some point in the past (12 months?) You can clearly see that because of the smaller new leaves. It is using it's reserves to stay alive and if no new roots come soon - big problems. The oldest leaves are always the first sacrificed for N - mainly - and lack of N is often accompanied by colouring.
> No point fertilizing the medium if there are no roots. Maybe a mist once a week with urea will keep the N up. otherwise, I have found with orchids in this state it helps to spray/water with very diluted auxins to get a root going. It's always a long way back though.


i took the plant out and the roots are minimal - i can spray with urea 46.0.0 weekly. The maximum you can water with auxins though is every 4 weeks - is that correct?


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## Elite Orchids (Jun 6, 2019)

Stone said:


> Yes agreed. This is very easy to diagnose. The plant lost roots at some point in the past (12 months?) You can clearly see that because of the smaller new leaves. It is using it's reserves to stay alive and if no new roots come soon - big problems. The oldest leaves are always the first sacrificed for N - mainly - and lack of N is often accompanied by colouring.
> No point fertilizing the medium if there are no roots. Maybe a mist once a week with urea will keep the N up. otherwise, I have found with orchids in this state it helps to spray/water with very diluted auxins to get a root going. It's always a long way back though.


out of interest what ratio of water to urea do you use for a spray? - thanks again


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## Stone (Jun 6, 2019)

Elite Orchids said:


> out of interest what ratio of water to urea do you use for a spray? - thanks again


I would start with 0.5 grms/litre and see if you get greening after a week or 2. A friend of mine here sells a hormone/B1 product which seems to work very well. It is rather weak so you can use it often. He also has a stronger one which is used only once. I think he posts worldwide. ''Vita grow H'' is what I use. He also has ''paph grow'' which is a paste to smear onto the base of the plant. to stimulate roots.
It has worked well for me but you need patience. https://floralaboratories.com.au/keikigrow-plant-hormones/vitagrow-h/


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## Ray (Jun 7, 2019)

I'll I agree with Stone on the use of urea in this case.

Orchid growers in general are quite "anti-urea", due to that rubbish about it requiring bacterial decomposition to be absorbed. While that may be required for rapid uptake by the root system (it's very slow if that doesn't occur), the leaves take it up much better than nitrates or ammonium compounds.

I think that the utility of a light switch is a fair analogy for auxin use: recommendations of frequent, dilute application are like walking past the switch and barely brushing it - you've made contact, but nothing happens. Apply the correct amount of pressure to the switch and the light comes on. Apply too much pressure (overdose the concentration) or apply it over and over (too frequently), and it can break.


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## Tom-DE (Jun 7, 2019)

sanderianum doesn't need strong light, especially for seedlings. You will get better growths under less light condition. The light level for mine is not more than 1200FC and it grows and blooms happily.

Strong light might have been the reason why the growths of your plant are getting smaller and smaller, which it is not a good thing........ If you don't correct your growing condition for your plant, the feeding is not going to do much IMO. If I were you, I would repot it and grow it less light first. Your plant still looks okay, so the new roots should come......


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## Ozpaph (Jun 7, 2019)

Stone, tell me how you use (and how much) the flora labs 'stimulants'. I have been soaking freshly deflasked plants in these before potting up. Not sure if it works.


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## Elite Orchids (Jun 7, 2019)

thanks all for your help so far - Tom what does IMO mean? it doesn't sound good. 

Attached are my tray of sandies - they obviously all get the same treatment, but some are quite dark while others are light in colour. i'll try the urea spray weekly. i already do a "kelpmax" spray every 4 weeks at 10ml per litre. 

other thoughts ?


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## Tom-DE (Jun 7, 2019)

"IMO"= in my opinion


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## Tom-DE (Jun 7, 2019)

Elite Orchids said:


> other thoughts ?



now it is more complicated....why not show people the other plants at first? or tell people it is the only plant having that problem........good luck!


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## Stone (Jun 8, 2019)

Ozpaph said:


> Stone, tell me how you use (and how much) the flora labs 'stimulants'. I have been soaking freshly deflasked plants in these before potting up. Not sure if it works.


Oz, The vita grow H (brown liquid) is used once a month or more often whenever you feel like the plant might need it. It is claimed to keep roots moving even over winter and I would not argue against this from what I've seen. The stronger one (red liquid) is used only once after deflasking. The paste is used on rootless paphs or to stimulate roots after dividing. I don't use any of them that often but when I have, I've noticed root stimulation with about 2 or 3 weeks - new roots from the rhizome and new root tips on older roots as well. Especially on mounted orchids where you can see them easily.
I'm not crazy about the idea of spraying leaves with them so I try to avoid that and soak the roots and lower stems only.


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## Ozpaph (Jun 8, 2019)

thanks


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