Seedlings are quite a bit more challenging imo and explaining what is more challenging or how to overcome those challenges is hard to describe, also most of us are also learning as we go still. I could link some basic care guides but you've read those.
As long as you know how much light to give, the right temperature for it and how much to fertilize it then the challenging part is figuring out how to water it.
ES has explained his method. Others never compact their moss. Then others don't use moss at all. There are lots of different media's that can be used.
Some media's can be overwatered so you have to water those carefully or the roots will rot. My preferred method is using media's that are hard to overwater. You can pick the right mix so that if you give it a quick spray once a week till a bit of water runs out the bottom, that will keep enough for a week but you couldn't do the same with sphagnum as ES described it would get too waterlogged.
But finding the right media for the environment and the plant you have comes from trying out different things unfortunately.
People always so do x y and z and never to repot too many times.
But what if the person trying x y and z doesn't follow the instructions 100% and ends up overwatering. Or the media is too compact. Long term the roots would rot. It is a very complicated matter if one gets really technical about it but it does help to understand what it is we as growers are trying to achieve - more so I find than what substrate we actually use. Sometimes the substrate size is more important. Are we using slotted pots that dry faster or regular pots that need more aeration because they have less ventilation holes?
Those are the important aspects we need to think about and get better at with every orchid we grow. We learn and try to do things better for the next orchid we get...
Here is an article to help explain (yes boring stuff but very good). The article is all about air porosity and talks about plants in general. As we know orchids need even airier substrates than regular houseplants- I would estimate up to 40% for Cattleyas, compared to the 20% they talk about in the article:
Air Porosity and Water-Holding Ability of Media Components - Sun Gro Horticulture
edit: the article mentions pore space, air holding capacity and water holding capacity.
To understand the article it helps to know that the air and water holding capacity is when fully saturated. So for example rockwool has 65% water holding capacity and 25% air holding capacity which gives a total porosity of 90% (65% +25%)
When the media is completely dry all pores will be filled with air. When the pores are completely saturated with water then some pores get filled, some retain air.
Perlite has a total porosity of 65% which is comprised of 40% water and 25% air when fully saturated.
bark has a porosity of 80%, 60% water and 20% air at capacity
coconut coir has roughly 90% posrosity, 80% water 10% air.
An interesting proerty of cocnut coir :
Quote:
In addition to providing for the water-holding and nutrient-holding capacities in a substrate, coir has been shown to increase the disease suppressiveness of a substrate. Researchers demonstrated that when plants were grown in substrates composed entirely or predominantly of coir (at least 60% by volume), the incidence of damping-off of seedlings as well as root rot of transplanted plugs caused by several fungal pathogens was significantly reduced.
Coconut husks may also be chopped to form small cubes that may be used as a substrate for such species as orchids and anthuriums. Shredded coconut husk or chopped husk may also be placed in grow tubes and used as a hydroponics substrate. The large particle sizes create
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although I am not a fan of coir, it holds 80% water vs 10% air so can be dangerous to use.
Moss varies widely, but genreally has something around 85% porosity, 70% water and 15% air