Perlite for semi-hydro

[blrnut]

Hi,

I'm trying to experiment semi-hydro with one of my phals. However, the only potting media that I'm able to get locally is perlite. The medium is not very coarse either The vendor mentioned that they are between 2mm to 5mm (~0.2 inch) in diameter. Are they too small for my experiment? I read in one of the articles that if the media was not coarse enough, the roots might rot. I was a little curious as there are quite a few orchids that folks try out in water-culture. So what exactly makes these roots rot.

Satish..

[cindiras]

Water makes the roots rot out. If you put one of your phals WITH GOOD ROOTS into water, those roots eventually rot off and the plant grows roots adapted to water. I would think Perlite would be a poor choice for S/H. It floats! How can it wick water when it floats on top? I have never triedto use perlite for my orchids, though. Has anyone else used it? What were the results? Satish, can you order Light-weight Expanded Clay Pellots (known as LECA) over the internet? I believe one brand -Ali-flor- is manufactured in the Netherlands. Is that a possibility for you?

[Halloamey]

Satish, I am successfully using perlite for my orchids for over 3 years now, never tried Semihydro with perlite though because as Cindi mentions it floats. LECA pellets are available in India in 3 different brands, One is Hydroton (very costly) Alifor and another local brand. PM me if you need to know the vendor from Pune.

[Undergrounder]

This is an old post but for the record,

Satish, yes perlite works fine as a S/H Medium, the water level in S/H is so low the perlite doesn't float. There are advantages and disadvantages for perlite over LECA:

1. Perlite is cheaper and much lighter to post.
2. It is well suited for finer root orchids and for seedlings IMO.
3. The particle size is small, which means it wicks water far better than LECA - The top stays wet, always, unlike LECA.
4. Water distribution through the pot is far more even than in LECA.

BUT..

5. Because perlite S/H is wetter than LECA, you get more algal growth, and the growth shows up more because perlite is white.
6. Perlite 'dust' is slightly annoying in fresh perlite. don't breath it in, but just wash it off before use.
7. Wet perlite 'sticks' together more, making repotting take longer. LECA 'rolls' making repotting faster.
8. Perlite is harsher on plants that are not used to S/H.
9. DRY pertlite can dessicate orchid roots if it stays dry for too long.. 100% perlite mix should only be used in a S/H setup, because if the mix dries out completely, it can injure the roots.

I use perlite on all of me S/H seedlings and a few of my larger plants. I've done so for about two years and results have been very good. It's now my
'go-to' media for sensitive plants. Still, most of my large plants are in LECA because LECA is an easier medium to handle at repotting time, and as far as growth goes, i've found little difference between the two media.

[blrnut]

Thanks for the detailed comparison, Undergrounder! I started S/H with LECA as a trial with 4 plants and been 2 months. 1 phal died due to crown rot as the water stayed for too long the others have been doing OK, except for a paph, which has not been able to put on new roots. Will wait for couple more months as the weather has started to warm up now, and the orchids should get into growth cycle.