Problems with SH- grow room details inside. PLEASE HELP!
 

So here's the lowdown:

Over the past year I've repotted maybe 20 orchids into SH. These have been a mix of catts, phal, oncidium, alcra, odontocidium, a few other variety I forget.

I've experienced about 75% success rate. I want this to be much higher... I notice on almost all of the new transplants the existing roots are becoming soggy, brown, and have small patches of white fluff.

When I repot, I pre-soak the hydroton in RO water with a little cal mag and superthrive. Then, I fill one of ray's pots or similar 1/3 full of the hydroton, place the plant in, full the rest while tapping the pot etc.

I let the plant rest for a couple days and then fill the container 80% full with RO water + 3/4 tsp MSU orchid fertilizer + 2 drops superthrive per gallon and let drain. The cattleyas, which are repotted from just rocks, I even dump the reservoir after watering so just the moist hydroton remains.

My grow room is about 65 degrees at night and 75ish during the day. The plants are located on a bookshelf against a West window. The ones in SH are sitting on a HydroFarm heatmat to provide underwarmth. I just started using the heatmat a month ago to try and speed up root growth. The top shelf of the bookshelf has a 200W compact fluero which is properly cooled. A desk fan flows directly on all plants all day as well as an oscillating fan 5 feet away. Humidity between 30%-65%.

I also repot everything with new growth only. It seems like it's always a race between rot and root growth. Worse case scenario the plant abandons all new green root tips and everything becomes soggy, etc.

I've saved most of them by cutting everything away, spraying it with organicide, and repotting into sphagnum.

Heres a couple pics. The first one you can see on the top of the bookshelf is where the fluorescent light is located:
http://i45.photobucket.com/albums/f8...l/DSC00626.jpg

http://i45.photobucket.com/albums/f8...l/DSC00646.jpg

and THANK YOU for any help!! Like most of you, I love my plants and am always striving to make them thrive a bit more.

Karl,

Success in converting a plant to semi-hydroponics is determined by several factors, not the least of which is how big the difference between the old- and new conditions in the pot. The more disparate, the more "difficult" for the plant.

Given that roots tailor themselves to the conditions they grow in, then don't change, you can understand why we expect the old roots to fail in the new conditions - unless the old conditions were also quite wet. That is why it is important that repotting be done just as brand new roots (not new growth on existing roots) are forming.

The fact that you sometimes see those new roots fail suggests that there is another factor paying a role. I would guess either too cool - consider the evaporative cooling from the medium; the heat mat will improve that - or you're not cleaning the medium well enough to start.

I am assuming that the MSU formula is for RO... If not, that's another issue.

Ray-
I understand that new roots have to form in the new conditions. The plants of mine that do well, their existing roots will first turn green and plump, sucking up water, then, once the new roots have dove 3-4 inches into the hydroton, ALL the old green roots die off and the new ones take off into the resevoir.

Don't know why they are all rotting out, though. I rinse the hydroton throroughly 3x then soak for an hour and rinse again a couple times.

Maybe I am misunderstanding you, but what you just described sounds pretty standard.

The scenario you mention about the old roots plumping up and turning green is an indication that the velamen is becoming saturated and translucent - as expected. That does not mean those roots are well-suited for staying that way, so the fact that they die is also to be expected - as it the fact that the new roots grow down into the reservoir.