Root Rot in large Phalaenopsis

[nutgirl]

This is a large double Phalaenopsis that I've had for several years. It had previously been potted in bark.

Last year (late spring/early summer) I changed it to S/H where it's been happily (or so I thought) growing. New leaves, flower spikes etc.

During the summer I noticed that I was not seeing any new roots forming from the main trunk (don't know the technical term) of the plants so I checked the roots and saw new root formation at the ends of the originals so fiqured that's what it was going to do in S/H.

Everything started to droop and go downhill last week so I pulled it up and the pictures tell the tale.

There were still firm, pale roots at the end of the mushy rotten roots but I don't think they were long for this world.

I cut everything off, separated the two branches and will start over with them again. They are currently in loose sphag until I see new root development.

What did I do wrong? Is it not a good idea to convert large mature plants to S/H since the existing roots can't adapt?

I'd like to know before I wipe out something else.

Maureen

[Zoi2]

Did you have new root growth before you potted in s/h?
How often were you flushing the pot with straight water?
I almost lost a couple of phals due to not flushing enough and they acted pretty much as yours is....they are now in water culture growing new roots, this spring I'll repot to s/h.
Joann

[nutgirl]

No, I didn't wait - should have- but when I saw new root growth in the LECA I though I was home clear.

I water all my S/H grown orchids once a week with weak fertilizer solution.

Maureen

[DelawareJim]

Maureen;

All the older roots die off like that when converting to S/H, which is why it's recommended to transfer plants when they start growing new roots. Keep it warm and humid and the new roots will adapt to the S/H conditions just fine.

The older roots die off because they are adapted to growing in the environmental conditions the plant was potted in before and can't change to the new conditions.

As an aside, I've been doing a lot of research into growing houseplants in Hydroculture which is very similar to S/H and has been huge in Europe for almost 40 years now. A lot of people cut off almost all the roots when converting their plants. They leave just enough root to keep the plant from falling over because all the old roots will die off. Some even unpot the plant after a month or 2 after converting to trim off all the old dead roots.

I also discovered this first hand with a Clivia miniata division I converted. All the old roots died off and the plant fell out of the pot. So I cut off all the roots, staked the plant, and a couple of weeks later, I had 4 roots growing out of the inner liner pot.

Cheers.
Jim

[nutgirl]

Jim,

Thanks for the converting to hydro info. I was wondering how they did it with well established plants.

I know I jumped the gun with this plant by figuring the new roots would soon start growing.

Live and learn. This year I'll be more patient and wait for roots then convert.

Maureen

[Ray]

Whether they succumb to the new environment is also related to what they were growing in prior to the move to S/H culture.

For example, if you grew it in a bark-based mix, it tends to be drier, so the move to S/H would be a drastic change requiring root replacement. If, on the other hand, it was in soppy sphagnum, the change would be a significant improvement in air supply without a reduction in moisture, so the roots would likely be fine.

You might also consider if temperatures played a role in the somewhat sudden demise.

This time of year, with colder, drier air, the evaporation from the medium can do some fairly significant evaporative cooling. Couple that with lowered nighttime temperatures to save heating costs, and the root zone can become uncomfortably cool for the phals - and they HATE that.

[nutgirl]

Ray,

I suspect temp played a part in it. We've had a dreary cold couple of months, even indoors.

It was planted in a gallon container and the middle of the pot - where most of the roots were - was probably pretty moist and cool even though the room temp was in the upper 60's.

I've learned a lot from this experience.

Maureen

[nibbler]

Can I ask do you always have such large root loss? I have just moved 7 of my 11 orchids into Semi Hydro. 6 Phals and 1 Dend. I did this to avoid killing the plants by over watering and suffering root loss.

[nutgirl]

Hi,

This is the largest plant that I have converted to S/H. Every other Phalaenopsis I have done has responded beautifully, but they were all much smaller, less established plants to begin with and they all had new roots forming when I did it.
I moved a Beallara with a large root ball to S/H last year. All the existing roots rotted but there were so many new ones it never skipped a beat.

After this one rotted, I checked the roots on all my others. It looks like most of their original roots have rotted but the new S/H roots are going like crazy.

After thinking about this one I have concluded it was probably a combination of not waiting long enough for new root growth to really get started and too cold a temperature this winter for the root zone in the pot.

I thought this was an interesting point from Jim:

Originally Posted by DelawareJim

Maureen;


As an aside, I've been doing a lot of research into growing houseplants in Hydroculture which is very similar to S/H and has been huge in Europe for almost 40 years now. A lot of people cut off almost all the roots when converting their plants. They leave just enough root to keep the plant from falling over because all the old roots will die off. Some even unpot the plant after a month or 2 after converting to trim off all the old dead roots.

So from now on I will only change to S/H when there is active growth and warm temps. (and I think unpotting after a month or so to check and clean things up isn't a bad idea. It doesn't seem to bother them. I've had the cats knock over enough to know.)

Hope this helps
Maureen

[nibbler]

It does thanks. I will keep an eye on them. Hopefully they will be ok.