Root explosion with daily watering | root issues | Questions regarding fertilizing

[Cymbidium]

Hi,

for about 2 to 3 month now I've been watering one of my Vandas in a bucket of osmoses water over night for about 7-10 hours. Considering the weight in the morning it seems to suck in about 1 liter of water.
Additionally I've wrapped the roots in a few strands of Synthic to help keeping them moist during the day.

After just a few days of watering the Vanda as described I noticed new root growth all over the roots (see pictures). I've stopped counting by 50+. And I find new root tips every day. So they seem to like it.

Regarding the Synthic I just don't know. What I like is that they really seem to help a bit with keeping the roots moist. What I don't like is that they are not pulling water up the strand, so you need to soak them completely.
So I want to test some micro fibre as I've seen on YouTube.

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Unfortunately I've noticed a problem with two roots about 3 weeks ago. One root started to shrivel and got dry. But what kind of made me uncomfortable was that it had some black spots. So I decided to cut off the root. Of couse I desinfected the cutting tool and I also used peroxide on the root and let it dry for one day.
Then I started noticing that the root got a little darker when watering. And this darker part is starting to grow. Now I am worried that I might have a fungal infection or similar.
So, whatever is going on I guess I should have waited a few more days before watering it again.

What do you suggest? Should I use Physan 20? Cut it again and let it dry properly? or?

And then there's another root which also starts to blacken and shrivel. Is this just normal or something to worry about?

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And lastly: Fertilizer. I am really struggling to get a hang of fertilizing my orchids. I have quite a few different fertilizers (as far as they are available in Germany) and want to alternate them.
I've also bought a tool to measure the µSiemens.

A few questions which I couldn't answer myself so far.

How do I fertilize / what quantity of fertilizer does the orchid need?
a. Soaking the orchid pot for a few minutes in the fertilizer mix, similar as I water them.
b. Just using a watering can and adding "a bit" of fertilized water to the already watered orchid?
c. Just spraying the roots (vanda)
d. Spraying the leaves
e. ???

What strength /µSiemens should the water / fertilizer have?
I've heard so many different statements, like weakly weekly. But then also that this way the orchid might not get enough fertilizer. Then once a month in full strenght, but then also that this way the orchid won't have continious access to nutritions... What about the Vanda. So far I've only sprayed my Vandas with Orchid Myst every second or so day, without any negative or noticed positive effect. But as it is quite expensive I won't buy another bottle.
On the other side I've fertilized a cattleya with 250 µSiemens just by putting the pot for 2 seconds in the fertilizer mix and got a few burn marks on new roots after a few hours.

I've read so much and seen so many Youtube-Videos about fertilizing orchids, but still I don't really know how to do it properly.

Hope you have some advice for me.

Thanks!

[camille1585]

First about your blackening roots: 1 rotting root on a large and otherwise healthy root mass may be nothing to worry about. It could also be to the very long daily soaks, which don't give the roots enough time to dry out in between, especially with those strips of synthic. Soaking 7-10 hours seems like a lot, 1-2 hours will also get the job done.


I think that you are overthinking the fertilization. If you consider the impact of various cultural inputs you provide to a plant, fertilization comes pretty low in the list. Getting the light, humidity and temperature correct (or within an acceptable range for the plants) will have far more impact that finding the "perfect" fertilizing regime.

You don't need to alternate fertilizers, find a decent one and stick with it. If by osmoses water you mean reverse osmosis water, I recommend that you get some Akerne Rain Mix, which provides the necessary calcium, magniesum and micro elements that pure water is missing. Yes, you probably have to order it from the nursery in Belgium, but a pot of it goes a very long way (and you can order some orchids with it! ) Akerne Orchids: RAIN MIX (R) The recommended doage of 0,5g/L (little scoop provided!) gives about 70ppm nitrogen

Weakly weekly is actually a very good way of feeding orchids. Why? Most orchids in the wild are epiphytes, growing up in the trees with their roots exposed. The only nutrition they get is what runs down the tree trunks/branches that they are growing on. So they get very low levels of nutrition.

How to apply it: generally people will add the fertilizer to the water the plants soak in, usually 3 out of 4 waterings. With daily soakings I'm not sure what is best, maybe other people will know better. I'd guess that you use fertilizer less frequently, even at low dosage.

About your fertilizer burn on the Catt. Either your EC meter is badly calibrated (which is common for cheap meters), or the burn marks are actually something else. 250 µS/cm corresponds to about 160ppm nutrition, and that is low. It's not possible to burn roots at the strength unless it's a very, very sensitive orchid (not Catts)! µS/cm also doesn't take into account the composition of the fertilizer. (What's are the NPK values of your fertilizer?)

If you want a good source of information on fertilization, check out Ray's very informative site (he's a member here) Free Information >> First Rays LLC

[Ray]

I'll agree with everything Camille wrote except the part where your conductivity measurement is corresponding to a certain nutrition concentration, as that's going to vary with the fertilizer used, which was not specified.

I suggest the following:

• Definitely use Akerne's Rain Mix if you're using RO water.
• Mix it up at a concentration of about 70-75 ppm N, which for that formula is 0.5g/L
• Measure the EC with your meter and write down that reading.
• From that point forward, you can use THAT EC for your mixing target.

[camille1585]

Originally Posted by Ray

I'll agree with everything Camille wrote except the part where your conductivity measurement is corresponding to a certain nutrition concentration, as that's going to vary with the fertilizer used, which was not specified.

I'm aware that the TDS of a given EC depends on the composition of the fertilizer, but rough benchmarks due exist. I was double checking it just now and see that it's not estimated the same way in the US and Europe. Here 1 ms/cm is said to correspond to 640ppm, while in the US its 500ppm. Perhaps I should have been more specific in my earlier post to saw it was a rough measure.

[Roberta]

Camille is spot-on in support of the "weakly weekly" regimen. Would you rather eat a huge banquet once a month, or a modest amount two or three times a day? Orchids are similar, they want a little bit of fertilizer fairly frequently, not a big amount occasionally. Also, they grow slowly, so they need very little fertilizer - fertilize too little and the plant may grow more slowly than is optimal. Fertilize too much, you'll burn roots and even possibly kill it. Err on the low side.

[Ray]

Originally Posted by camille1585

I'm aware that the TDS of a given EC depends on the composition of the fertilizer, but rough benchmarks due exist. I was double checking it just now and see that it's not estimated the same way in the US and Europe. Here 1 ms/cm is said to correspond to 640ppm, while in the US its 500ppm. Perhaps I should have been more specific in my earlier post to saw it was a rough measure.

I was not aware there WERE "standards" in that arena!

Where I was coming from is based upon a comparison of the MSU RO formula (13.2-3-15-8Ca-2Mg) and K-Lite (12.9-1.3-1.3-10Ca-3Mg). Both have the same level of trace elements, so for the same nitrogen level in a solution, the MSU RO formula has about a 45% greater TDS, but only 11% greater EC.

[camille1585]

Originally Posted by Ray

I was not aware there WERE "standards" in that arena!

Where I was coming from is based upon a comparison of the MSU RO formula (13.2-3-15-8Ca-2Mg) and K-Lite (12.9-1.3-1.3-10Ca-3Mg). Both have the same level of trace elements, so for the same nitrogen level in a solution, the MSU RO formula has about a 45% greater TDS, but only 11% greater EC.

Interesting that the difference in ppm is so large! You have far more knowledge in this area, so I'm happy to learn more. I had come across those 'standards' late last year when doing a project at work with an American company. We had to copy their protocol for growing a certain crop, and they refer to fertilization in ppm, while we use EC. I had found that 'standard' online to have a rough idea of what EC we should be feeding, and luckily we found more detailed information on the manufacturere's website (saved us a lot of calculations!)

[Ray]

Camille, in my mind, it is that discrepancy that makes TDS a terrible control factor.

Most professional growers of commercial greenhouse crops here use "ppm N" as their controlling factor, having selected a formula that provides the correct balance of nutrients. Fertilizer manufacturers provide the EC versus ppm N data, so an EC meter becomes the easy-to-use tool for controlling the concentration.

For example, poinsettia growers all target for 1/2 gram of nitrogen fed to the plants over the time period from the planting of rooted cuttings to harvest. They know the volume of the pot and the solution retention of their medium, so by knowing the time to harvest and frequency of watering in their controlled greenhouse environment, they know what concentration of fertilizer to apply, so that the seasonal sum is 0.5g N.

TDS meters are just cheap EC meters with a built-in standard conversion factor, and as my example shows, There really cannot be an accurate "standard".