Two comments:

For phalaenopsis, I recommend a much broader, and likely shallower pot. Do not be afraid of "overpotting" with S/H culture; the LECA spreads the moisture far more evenly, so there's no "soppy center". Plus, aerial roots will tend to enter the pot that way, making it more stable.

The root-tip death is due to desiccation. LECA is VERY absorbent, so if a root tip comes in contact with a dry pellet, they will extract the moisture from it. A shallower pot, more frequent watering, or even better, raising the humidity in the growing area, can alleviate that.

I have a couple of questions. This will be my first winter in semi hydro. I keep my "warm growers" in a room that right now ranges between 28°C during the hottest hour of the day and 20°C at night (82°F - 68°F). It's still really warm in Mexico City. I glued one of those cheap aquarium thermometer stickers to one container and the temperature inside hasn't dropped from 20°C. So my question is, when should I fire up the heat mats? And will it affect the blooming cycle?

To answer that, one has to consider two aspects:

1) Is the plant's blooming affected by temperature? Of typically-grown orchids, phalaenopsis are the most common in which that answer is "yes". But if it has already seen the required period of average temperature reduction, heat mats are no issue, and may actually help the growth and blooming.

2) How is "warm-growing" defined? Many cattleyas, for example, are warm-growing, but have no issues with a moderate chill. Phalaenopsis, on the other hand, are actually more "hot-growers" than "warm", but are pretty tolerant of warm conditions. They will not do well with chilled, wet roots.

My growing area has winter temperatures like yours in the day, and cooler at night. I don't use a heat mat. My Phals do fine.

Do you think a good spraying with water onto the root and surface of the LECA will assist in getting the roots past the upper layer? I have natural humidity and my dry line is only 1-2 layers down.

I was thinking of making a little hole by moving the beads around and letting the root go down before covering it over again?

Does the dry line affect some orchids more than others? My cattleyas are not bothered at all and neither are my oncidiums. Hopefully the den-phals will be OK, it's my first time growing these.

I think the issue with spraying is the need to do so very often, to keep it moist.

You might consider a plastic cover or film "tent" over the top of the roots and the pot.

One decent idea I've seen was to make a round, clear plastic "cover" out of a vinyl page protector sold at Staples and the like. Make the disk be about 1" smaller in diameter than the pot, cut it radially to the center, and remove a portion in the center, about an inch bigger than the base of the plant. The gaps allow you to water with it in place, and it still allows air flow, but some of the evaporating water will condense on the plastic and drip back into the pot.

Hello,

I’m glad to see you kept up-dating this post. It is very interesting. I intend to get Cattleya and grow them in SH.

I wrote in March, to tell you, that your post gave me the little push I needed to start the SH with Cyrtocidium (Wilsonara) kolibri.

http://www.orchidboard.com/community/836927-post19.html

At the time I got the Kolibri, the roots were in a bad shape, they were pretty much all rotten. Any how, it is doing pretty good now. The pseudobulb even plumped.

I also decided to grow in SH, a Schunkeara (Beallara), a Miltoniopsis and a other Oncidium (Odontoglossum type one), that I got shortly after, and they are all doing pretty good.

Only two of them have algae and they are the ones for which my wather reservoir are glasse one. The two other one are white opal reservoirs. I was told that algae need light to form. Maybe that algae will eventually form with time. However, it does not really bother me but it would be nice to avoid it.

Any time there. Is a combination of light, water, and fertilizer, there will be algae, but it really does no harm.

Once it has appeared, you don't want to kill it in place; it's bettering to repot and then clean the old one. Preventing it in the first place is the key.

For folks using clear or translucent pots, I used to recommend a monthly watering with a disinfectant like Physan, but I have since learned that algae growth is very often an indicator of over-fertilization.

When I reduced my feeding from 125-, to 25-35 ppm N at every watering, I no longer had an algae issue, and my plants actually grew and bloomed better than ever.

I used to worry about algae and what would happen when it builds up a lot. But it looks a lot worse than it really is. It's confined to the inside of the pot walls and I've learned to co-exist with it and ignore it.

I was going to try the pot covers that Ray suggested but I decided I will first try increasing my frequency of waterings to address the dry root tips. Rather than waiting for the reservoir to go down and misting the top, I will just water those ones perhaps 2 or even 3 times a week until the roots go down. I enjoy watering my orchids so this should not be a problem and they seem to respond well to frequent flushings. Unless that is just my imagination! I won't be fertilising them every time though. I will probably alternate fertilier and plain water so that I am not wasting it. Especially on orchids that are not quite fully established.

As for updates, vanda seedlings are not doing much, cattleya seedlings are going nuts. Oncidiums looking plump and miltoniopsis leaves growing smoothly and reasonably quickly. Paphiopedilums are alive and just plodding along - no signs of distress but really difficult to gauge what's really happening in the container. Phals are doing fine with the cooler and dim weather in the UK. We are getting near to freezing at night outdoors, though of course they live inside with central heating. I'm not out of the woods but they look a lot better than they did last year.

I'm very much looking forward to my new den phals to get established so that they are able to support themselves a bit better.

I was watering my orchids today and enjoying that I can water everything all at the same time. I was struck by how healthy everything is looking. I recently threw some IKEA den phals into semi hydro and they seem to be doing well.

Many of my orchids including cattleyas, phals and oncidiums have roots down to the reservoir with no apparent issues. It is nice to know the LECA does not break down and I won't have lots of repotting to do this spring. The only orchid for me that did not like semi hydro were vanda seedlings and TBH I expected them to hate it (but I wanted to see how it would go as an experiment).

My phals are doing great in semi hydro, no issues with it being winter/cooler but I did the conversions at a warm time of the year so they could settle in before the winter came. Only 4 out of my 20 phals did not spike yet this season but they are in the lower light window so I think they will bloom in spring.

I only have one big cattleya in bark that I am afraid to disturb and one phal left in moss. I have around 50 or so orchids in S/H and could not be happier with the technique. My paphs seem totally unaffected by the transfer to semi hydro.

The only orchids that I grow routinely in bark now are the cymbidiums which I keep in the garden year-round. The cymbidiums are so big that I am happy just to carry on with Orchiata for these.