Multiple problems with my orchid!

[WaterWitchin]

Originally Posted by Token

This is good advice, the person that invented semi-hydro was clearly an inexperienced person and semi hydro has been around for 40 odd years yet nobody questions that it does not really work for exactly the reasons Ray has posted.

The other thing you will see orchid beginners try out to kill their plants is douse their roots with 3% Hydrogen peroxide.

Bad advice seems to linger and those 2 I keep see beeing used badly again and again

I totally disagree with the semi hydro comments Token. You obviously haven't successfully grown that way, but it doesn't mean many can and do.

I totally agree about using peroxide on roots. Bad advice has always been with us in many ways, and always will be. In many ways, shapes and forms.

[Ray]

Originally Posted by Token

This is good advice, the person that invented semi-hydro was clearly an inexperienced person and semi hydro has been around for 40 odd years yet nobody questions that it does not really work for exactly the reasons Ray has posted.

That comment kind of “got to me”.

1) I am the guy that “invented” semi-hydroponic orchid culture.
2) S/H works because the physical properties of the medium prevent suffocation.

With any potting medium, when we water, most of the liquid pours right through the medium. Some of it is immediately absorbed by the plant and the potting medium, but there is a third portion that is held between the particles by surface tension.

When using 8-16mm LECA as a medium (that’s a pretty standard size) the size of the void spaces is large, so that “bridging” water can only be in the immediate vicinity of the pellet-to-pellet contact points, leaving lots of open volume. Additionally, LECA is pretty good about “sucking up” the small amount of bridging water, so it will go away relatively quickly, too.

Compact sphagnum moss is pretty much the other end of the spectrum, as the voids in it are so small that they can be completely filled with bridging water, cutting off the airflow to the roots, suffocating them.

Even a nice, coarse bark mix that started out more LECA-like in its water capturing capacity, will decompose into smaller and smaller particles, resulting in a greater and greater amount of bridging water, and then suffocation.

[camille1585]

Originally Posted by Token

This is good advice, the person that invented semi-hydro was clearly an inexperienced person and semi hydro has been around for 40 odd years yet nobody questions that it does not really work for exactly the reasons Ray has posted.

The other thing you will see orchid beginners try out to kill their plants is douse their roots with 3% Hydrogen peroxide.

Bad advice seems to linger and those 2 I keep see beeing used badly again and again

Regarding semi-hydro, there is a massive difference between waterlogged and growing a plant very wet. Pore space explains this difference. Pores can be filled with air or water and what the ratio is will depend on how wet/dry the substrate is, and what the pore size is. In an old organic mix free water doesn't drain well anymore because as the substrate degrades, pore size gets much smaller. If air can't easily replace water in the pores, then you have no oxygen and the roots suffocate and die. Now look at semi-hydro. The system is designed to have very high pore space, both inside the leca balls and between the balls. The larger gaps are what allows the water to easily drain out, and why it's nearly impossible to overwater in S/H. Basically, the system is designed to have lots of air around the roots.

I'm not sure where you got the idea that S/H doesn't work. Most failures come from improper timing of repotting, or an environment not suited for it or the plant in question. S/H is not a one size fits all solution, no substrate or potting technique is.

As to your second remark, I guess you noticed that the forum does an excellent job of trying to combat the bad advice about dousing the roots about H202. Lately it does frequently pop here, but people are picking up the information elsewhere on internet, then happen to mention it here when asking for help with an ailing orchid. In the responses to those posts, forum members will nearly always advise to NOT use H2O2 on the roots, or anything for that matter given how sensitive roots are.

---------- Post added at 08:17 PM ---------- Previous post was at 07:42 PM ----------

Oops, I missed the second page of posts, and see that Ray already responded similarily...