Dinema root tip burn - Orchid Board

Steve83 · #1 08-25-2020, 08:14 PM

MY Dinema polybulbon is constantly getting burnt root tips, cannot figure out why. It is mounted on cork and receiving identical care to my other mounts, E. porpax and E. Porpax var alba (also on cork).

It will put out roots that look great for a few days, and then they'll just turn black at the tip, and resume putting out more roots. It has also grown a number of new pseudobulbs, with no leaf tip burn.

Temps for it have been in the low 80s f, and humidity dropped to 60% today. The last feeding was 2 days ago (Sunday) and I mixed MSU fertilizer with RO water. My TDS reading was 150ppm if I recall correctly.

The newer roots looked great yesterday with green growth tips, and even when I checked on them this morning.

I have been lightly misting the mounts with only RO water maybe 3-4 times a day (if the roots are white). Is that possibly causing it (no nutrients)?

estación seca · #2 08-26-2020, 01:05 AM

If you look at the habitat photo on IOSPE (which lists it as Encyclia polybulbon) you will see it growing in a bed of moss on a tree branch in cloud forest. I doubt the roots are completely dry more than a few hours a year.

Ray · #3 08-26-2020, 09:05 AM

Quote:

Originally Posted by Steve83

Temps for it have been in the low 80s f, and humidity dropped to 60% today. The last feeding was 2 days ago (Sunday) and I mixed MSU fertilizer with RO water. My TDS reading was 150ppm if I recall correctly.

The newer roots looked great yesterday with green growth tips, and even when I checked on them this morning.

I have been lightly misting the mounts with only RO water maybe 3-4 times a day (if the roots are white). Is that possibly causing it (no nutrients)?

RO water would do nothing damaging.

TDS meters are notoriously bad for measuring the true content of a fertilizer solution. Is that the MSU RO formula @ 13% N? How much are you mixing in a gallon and how often are you applying it?

Steve83 · #4 08-26-2020, 09:22 AM

Ray, yes it's the MSU RO formula (13-3-15). The last application was Sunday.

This morning I mixed a little over 1/4 tsp to a gallon, for a reading of 200ppm.

I also moved it to a cooler area of the tent this morning, and backed off the light a bit.

The reason I wondered about the possibility of over spraying with just RO water, was if it could be from lack of nutrients (like with leaf tip burn due to lack of calcium), or just burning of the wet green tip due to the light intensity.

Ray · #5 08-26-2020, 11:35 AM

Quote:

Originally Posted by Steve83

Ray, yes it's the MSU RO formula (13-3-15). The last application was Sunday.

This morning I mixed a little over 1/4 tsp to a gallon, for a reading of 200ppm.

1/4 tsp/gal is about 40 ppm N, which is fine for used even a couple of times a week and should not do any "burning" whatsoever.

Your 200 ppm TDS reading is suspect though. At 40 ppm N, the true TDS (g fertilizer per kg water) is about 300 ppm. (Read this)

Quote:

The reason I wondered about the possibility of over spraying with just RO water, was if it could be from lack of nutrients (like with leaf tip burn due to lack of calcium), or just burning of the wet green tip due to the light intensity.

Neither of those is possible. If the root tip got hot enough for sun damage, the water would evaporate and cool it.

Leaf tip necrosis is due to calcium deficiency as cells form, so they simply do not form correctly. It is not a case of them growing fine, then dying back - although that is what it looks like. Watering does not "extract" anything from the plant. If the roots were fine, then crapped out, the issue is ether toxicity or a cultural deficiency.

Steve83 · #6 08-26-2020, 02:47 PM

Well, I'm just going to document it's daily culture to see if I can figure it out.

I've realized it's going to be best to systematize everything, especially since I have so much control over environmental parameters in the tent.