Paph roots rotting

[Markedg]

I am having issues on some of my paphs with root rot. This mostly affects the multiflorals. I live in Dublin, Ireland and grow my orchids in a 10x12 foot greenhouse. I have potted them in medium, straight bark in pots that are just big enough for the roots. I water them when the pot starts to feel lighter, about 1x a week. I have been buying either nbs or bs seedlings from a well known breeder. Most of them are doing fine, and a few are even showing spikes. They will look fine to look at, growing a few side shoots but no roots. For example, I have a paph phillipense that looks fine. I nearly knocked it over but I was able to stop it. I then noticed that the plant had no roots but had a few very short ones starting. There are just a few of these plants doing this. I have quite a few other paphs and they are growing away happily.

I have always read that paphs could be repotted at anytime but I have read in a few places that this is not correct. That once you repot your paphs, it has to regrow new roots. In the fall and winter here, the light levels go down by quite a lot. It does not get bright until 8:30am and it is dark by 4 pm. I am not sure if this could be an issue.

Would anyone have any idea of what I could be doing wrong? I appreciate any help you could offer me with this problem.

 

[TyroneGenade]

The medium is probably too acid. Mix some shell grit, dolomite, limestone, crushed brick chunks into the mix. This has helped for me.

Also, if it takes a week for the plant to dry out then for a lot of that week the medium is probably too wet for the roots. The stony material in the mix will help with this.

 

[Justin]

What is your water quality? Have you tried a reverse osmosis filter? High total dissolved solids & high salt levels in particular can be detrimental to paph roots. R/O water (some also use rainwater) makes for awesome root growth.

 

[Darin]

I'd repot and use a bit looser mix. Something to open up the airspaces (charcoal, gravel, sponge rock, etc).

 

[NYEric]

I then noticed that the plant had no roots but had a few very short ones starting. There are just a few of these plants doing this. I have quite a few other paphs and they are growing away happily.

This is good, it seems to be trying to grow roots. add some open media like horticultural charcoal, and perlite. Also, are you fertilizing? Try the revised media, a little more water, and some light fertilizer.