Newbie--Laelia Anceps Guererro In-Bud

[estación seca]

In Minas Gerais near the town of Diamantina, Laelias grow on top of very flat rock benches 1 meter wide that emerge about 20cm / 8 inches from the surrounding white quartz sand, and extend in straight lines for many meters. Geologically these benches are newer igneous intrusions into cracks in older quartz; the older rock has weathered down to a field of white quartz sand, common in MG and Bahía.

Small amounts of organic matter accumulate on the bench tops, mixed with the sand. Bare rock is not visible on the top surface. There was almost nothing taller than grass. I was there during the dry winter, and the Laelias were purple from sun and cold, almost leafless. In the rainy season the benches are wet, and the surrounding sand below the benches often under a few cm of water.

Lithophytes from hot-summer areas rarely grow on bare rock. It's too hot. They grow in mats of decaying organic matter about 1-2cm thick that are wet to damp throughout the rainy season. Roots extend far laterally, but only under the organic mats. The bare rock between the mats is bare. I have seen this in México, Madagascar and Brasíl. If I remember I will try to dig up photos.

[rbarata]

Thanks for the info, ES.
Quartz are acidic rocks, I think, and one on the components of granit.

Originally Posted by estación seca;

If I remember I will try to dig up photos.

It woyld be great! Thank you!

[Roberta]

I think that quartz is chemically quite neutral, since it is very insoluble at any pH that is likely to be found in nature.

[SirCatofBloominCheshireC:]

[QUOTE=rbarata;831666]Mr. Cato... or should I say SirCato?
Sorry for hijacking your thread.

I don't have a problem with anyone hijacking the thread at all. I enjoy the new information and where the thread will go with the questions and answers.

---------- Post added at 10:01 PM ---------- Previous post was at 09:59 PM ----------

Originally Posted by Roberta

Which Encyclia?

It is Encyclia Hanburi. One day I hope to get ahold of encyclia fowliei as well. What is your favorite Laelia and Encyclia?

[Roberta]

Originally Posted by SirCatofBloominCheshireC:

It is Encyclia Hanburi. One day I hope to get ahold of encyclia fowliei as well. What is your favorite Laelia and Encyclia?

I do have E. hanburyi too... and it is pretty bulletproof. My favorite? I think, whatever is in bloom at the moment. I do love L. anceps.... I wish they lasted longer, but have acquired enough of them (with some variation in bloom time) that I manage to have at least one of them in bloom from late October or early November to February (still have a couple in bloom) But ask me in the late spring, and it would be L. purpurata. And the little rupiculous Laelias give so much color and last for a month or six weeks, if a plant has several spikes that don't all bloom at once, it can be in bloom for two or three months. So I love them too. In the Encyclia department it would probably be E. (Prosthechea) radiata which smells wonderful or E. (Prosthechea) cochleata that blooms sequentially for months. Both also quite bulletproof.

[rbarata]

I think that quartz is chemically quite neutral, since it is very insoluble at any pH that is likely to be found in nature.

I don't mean that quartz gets dissolved. The key here is silica. Take a look at this page, especially the section called "Rocks in the soil".

ES mentioned "...igneous intrusions into cracks in older quartz.". From his descriptio,n the rock benches are probably made of granite (over 70% of silica) and I'm assuming Laelias have evolved to to live and grow in "soils" with ph<7.
So, using silica based rocks/sand is a good measure, I think,

[Roberta]

If the pH is <7 I think it would be due the the organic matter in those cracks. Crystalline silica (SiO2) - quartz - Isn't going to contribute much of anything... the only things that break those bonds are hydrofluoric acid and strong alkali, the latter also needing high temperature to do more than attack the surface - caustic (concentrated sodium hydroxide solution will etch glass a bit), one can convert it to a soluble form (sodium silicate) by fusing with sodium carbonate at a temperature high enough to liquefy them both (like over a Bunsen burner flame) And sodium silicate is alkaline, since sodium is a much stronger base than silicate is an acid. If there are soluble silicates around, I think it highly unlikely that they came from quartz. Diatomaceous earth may have small enough particles of silica and enough surface area, but even that isn't going to change the pH much in nature.