# Root growth time, should I fertilise the plants?



## Hyun007 (Dec 25, 2016)

It is the raining season in Koh Samui, Thailand. The weather and the rain water seem to encourage more root growths, new leaf or new growth on those active as well as those that have been idling for months.

Many new small roots coming out of my Parishii. My only question is should I fertilise it. In the past, when I use 20-20-20 weekly on the new roots, it stopped the root growth. I have no idea whether it was the weather or fertiliser issue.

I have not fertilised it for more than 2 weeks now because of the regular rain(some heavy one, including a 96cm rain for 4 days!) and the new roots growth looks good and I am unsure of what I should do. Please advise, thank you.


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## Ray (Dec 26, 2016)

Most orchids are not particularly demanding of fertilizer, so a couple of weeks of none won't hurt anything, but I would have to ask about the concentration of the fertilizer you used... For example, for a 20-20-20, I would never apply it at a concentration greater than about 0.65 ml/L. My preference is to feed at every watering, and with that formula, I'd use 0.1-0.15 ml/L.


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## Hyun007 (Dec 28, 2016)

Ray said:


> Most orchids are not particularly demanding of fertilizer, so a couple of weeks of none won't hurt anything, but I would have to ask about the concentration of the fertilizer you used... For example, for a 20-20-20, I would never apply it at a concentration greater than about 0.65 ml/L. My preference is to feed at every watering, and with that formula, I'd use 0.1-0.15 ml/L.



Thank you Ray, that information is extremely helpful.

I was thinking of 13-13-13 which one friend said he is going to be using, now your daily light fertiliser is also a very good choice.


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## Ray (Dec 28, 2016)

A 20-20-20 and a 13-13-13 are the same formula fertilizer, the second being 65% of the concentration of the first. If you're going to use the 13%N formula, my recommendations would be to take the numbers in my prior response, and multiply them by 1/0.65=1.54.


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## gonewild (Dec 28, 2016)

Ray said:


> A 20-20-20 and a 13-13-13 are the same formula fertilizer,



Ray are they the same formula or the same ratio? 
If they are the same formula they would need to be made from the same chemicals and contain the same type of nitrogen. One may be made with all Nitrate nitrogen and the other all Urea.


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## Ray (Dec 28, 2016)

True enough, Lance.


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## Ozpaph (Dec 29, 2016)

weak, weekly


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## Hyun007 (Jan 1, 2017)

Thanks all for the inputs. Any idea when is a time for me to stop fertiliser? My tropical climate is different from most of you guys. I should just continue weekly throughout the year?


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## Ozpaph (Jan 2, 2017)

If they are growing, fertilize.


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## paphioboy (Jan 3, 2017)

Food for thought: In sub-tropical and tropical countries where heavy monsoons are common and occur seasonally, wouldn't this be a period where heavy runoff and leaching of nutrients occur? Coupled with overcast days, is it a good idea to give fertilizer during this period?


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## Stone (Jan 5, 2017)

paphioboy said:


> Food for thought: In sub-tropical and tropical countries where heavy monsoons are common and occur seasonally, wouldn't this be a period where heavy runoff and leaching of nutrients occur? Coupled with overcast days, is it a good idea to give fertilizer during this period?


From the studies I've read, the rainy season gives the most dilute concentration of nutrients but, obviously, they are constant. So Ray's ''a tiny bit all the time'' would be good then.
You have to be careful when it's hot as well. Many plants can be injured with a combination of high heat and high fert. Tanaka suggests stop feeding in summer and start again in autumn. But I think Tokyo does not have the cooler summer nights that I have here.


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## Hyun007 (Jan 5, 2017)

paphioboy said:


> Food for thought: In sub-tropical and tropical countries where heavy monsoons are common and occur seasonally, wouldn't this be a period where heavy runoff and leaching of nutrients occur? Coupled with overcast days, is it a good idea to give fertilizer during this period?



My area is currently having heavy monsoons for the second time in a month! It will last another few days. Many areas were flooded. I am wondering how am I going to fertilise the plants with the continous rain as I already missed the 1 week cycle. It is not possible for me to bring them inside the house or shade from the strong wind and heavy rain.


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## Hyun007 (Jan 5, 2017)

Stone said:


> From the studies I've read, the rainy season gives the most dilute concentration of nutrients but, obviously, they are constant. So Ray's ''a tiny bit all the time'' would be good then.
> You have to be careful when it's hot as well. Many plants can be injured with a combination of high heat and high fert. Tanaka suggests stop feeding in summer and start again in autumn. But I think Tokyo does not have the cooler summer nights that I have here.



Hmmm.....I will change to very light fertiliser during the hot season. Thank you for the information. I do need to know how to fertilise them if it continue to rain every day.


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## paphioboy (Jan 6, 2017)

Stone said:


> From the studies I've read, the rainy season gives the most dilute concentration of nutrients but, obviously, they are constant.



Agreed, but does the water carrying diluted nutrients stay on the surface long enough to be absorbed by the root velamen? 



> My area is currently having heavy monsoons for the second time in a month! It will last another few days.



Same situation here in northern part of Malaysia/Thai border (Golok river side). My opinion is not to fertilize at all, or only a little bit for plants that have new growths with a flush of new roots.


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