Diatomite Mix in a Home Setting

[work2ski]

Back in 2004, I went in with the hype of a new orchid mix that can't be overwatered with the primary ingredient => diatomite. They just forgot to mention that the rocks would suck the life out of your orchids if left dry for a couple of days.

Within 3 mos. of repotting with this, I loss a fair share of Onc, Mtssa, and some Brassias due to rotting because of too much moiture retention in the coir mix. Immediate moved these type back to a to a bark/charcoal mix and managed to salvage a few (summer of 2004).

Didn't know why I didn't learn from that and went out and bought more straight diatomite to use in my bark mix (replace the sphagnum portion with them). Afterwards, I made a close observation, especially on the phals. Any newly glistened root(s) that touch a piece of diatomite would start to shrivel away within days.

I repotted almost all of my plants this week-end and found no rot. Just severe dehydration on the root system (the roots that grew on or around a piece of diatomite is either dead and dry or severely deformed due to lack of moisture).

I am not sure how they are in a greenhouse culture with the frequent dampings but in a home/window setting, it is fatal to my orchids. Of all the things I am unsure about orchids, this I am sure. Because I don't have the luxary and time to keep a tight watering schedule, any delay in the watering would be deadly to the roots.

Only the phrags seem to do well in the mix but even then, they are all going into s/h. I don't trust this stuff because I have been using it for over a year now with horrendous results (except for the phrags).

For the gurus that have mastered using this material, I tip my hat to you.

Trung

[jtlqh]

Is lava rock different than diatomite? I just started to use them on my catt, onci, your post got me worried.

Qing

[Diane]

NO!! Lava rock is not Diatomite! I have some Catts that absolutely refuse to grow in anything but lava!!! I always have a bag of lava on hand. If you want something like that and don't feel comfortable with lava, you can use those clay pellets that they use for semi-hydro.... although I think those pellets may actually retain more water than lava....

Hmmm... I see and experiment in there somewhere.....

[Gin]

Here is my 2cents worth , a couple of years ago I recieved a Catt. in straight diatomite ... I grow a lot of Catts. in the pellets and all is well .
Not in the diatomite , thinking it would dry fast I watered along with the rest of them .. rotted the roots off it .
From what I have read it holds 150% of it's weight in water .
No problem with lava rock altho I have read it retains more of the Fertiliser salts than the pellets , both need to be flushed with clear (lots of it ) water off and on . I grow in a greenhouse . Gin

[work2ski]

Qing,

Diane is right lava rock is not diatomite. All my dens sit in straight lava rocks. Sometimes I would forget to water them for days and the roots are always OK. With diatomite, signs of dehydration to the roots are very visible and obvious. I will repot what's left tonight and will post some pics to give you an idea.

[uncasteeb]

I suppose without using a res the pellets would dry out very quickly & would be very difficult to get them wet again.
I leave a bucket full of pellets(LECA in my case) for weeks & weeks until i need to use them .
The 2 Catt species i have are in s/h but only have a very small res(about 1/2 the size i normally use) & the plants are growing nicely.When i used the normal size res the plants sulked & hardly grew.
I have been trying many different types of mixes for my Paphs & after about a year the plants in 1/2 bark & 1/2 LECA seem to be growing the best.Difficult to say as individual plants grow @ very different rates.

[work2ski]

Steve,

These are not pellets, and as far as I know, they are not used in a s/h setup. Seems to be a growing trend in my area for the growers to use them in place of sphag, but again, they are in a controlled env. in which the watering system is automated, with frequent dampenings. In my home, I have never seen anything that wick moiture out of the roots as fast as them. Just count my blessing that it hasn't caused any fatalities yet.

Hope the pics speak for themselves.

[Diane]

Boy those are some pretty unhappy looking spots on those roots! I guess I'll stick with my tried and true home mixtures...

[work2ski]

The bad thing is without seeing the roots, I would not have a clue. Leaves are upright and shiney. Look at the last picture. It happened to every single one of them. None of the new roots would make it very far after touching a piece of diatomite.

Noticed it a while back. I was just to lazy to repot and figured the post will help those who like to experiment with new mixes. No need for trial and error with this one.