About adding limestone or not, and the use of dolomite
Posted: Thu Jan 26, 2017 4:33 pm
First of all I’d like to apologize for asking something probably already discussed many times in the Forum. But the Forum is something alive and there always will be newcomers with the same old questions. I’ll try to put in a different way and also I would like to say that I read lots of posts before formulating this question. But, again, I know this is not new…Anyway…
As I live in Brazil, most of soils are naturally slightly acid, and the pH of tap water is neutral. So, for me, the issue about substrates pH is a matter of add or do not add limestone or calcareous rocks. I currently don’t do that, and, without taking any measure, things will be good, on average, for most of my cacti.
On the other hand, I like to know about the natural habitat of my plants. Also, I’m interested on which kind of rocks and minerals they grow and which kinds I’m using. I’m aware that once the soil is inside a pot, it will not behave as it would do in nature, so it’s almost impossible to reproduce the soil of the habitat in a potted collection. Even knowing that, I’m still interested in the habitat. I use to search for images of a given species in its habitat, so I can have some clues about their natural environment, such whether the soils is sandy, humus-rich or a rocky outcrop. As much as possible, I would try to reproduce that, just for fun.
Finally, following other member’s experience, I’m more and more interested in grow my plants in soil-less, rocky substrates. When you start growing some cacti on pure mineral mixes, the kind of minerals that are being used gain new and higher importance. That’s why I’m here trying to objectively ask some questions about that (Ok, I know, I’m not being objective ).
So, how do you guys make a decision about adding limestone or calcareous rocks to the potting mix?
(a) I never add limestone and I avoid calcareous rocks
(b) I always add limestone and/or calcareous rocks
(c ) if the cactus is South-American, I don’t add limestone and avoid calcareous rocks; if the cactus is North-American, I add limestone and/or use calcareous rocks
(d) I search for information about the habitat and whenever is said that the soil is alkaline, I add limestone/calcareous rock
(e ) I don’t care
For example, I have a Mammillaria hutchisoniana, which is from Baja California. Finding information about Baja California soil can be tricky. At a first search, I found some references to soil alkalinity, but going a little deeper, I found out that the region is a mosaic of soils, and another Mammillaria species (phitauiana), also native to Baja California, likes acid soil because of the particular characteristics of its particular locality. As I don’t have any information about the exact locality for M. hutchisoniana, I can’t say for sure that it likes more alkaline soils. As a conclusion, I would get crazy if trying to find specific information for each species and try to give them these specific conditions. As result, I give up (option “a” above).
How do you guys usually deal with this?
Is there, somewhere, a list of cacti species with information about their locality and /or some information about it’s soil preferences?
This post is already too long, but I also would like to ask if calcareous rocks effectively will affect pH; in other words, should we bother about that or not?
In fact, I started this thread because I found a good and cheap source of ground dolomite, and I would like to use it in the sowing mix. Will it be a problem to Notocactus, and good for Thelocactus? Or it doesn’t matter at all?
here is a picture of the ground dolomite:
Thanks for your patience in reading all this, any comments are much welcomed.
As I live in Brazil, most of soils are naturally slightly acid, and the pH of tap water is neutral. So, for me, the issue about substrates pH is a matter of add or do not add limestone or calcareous rocks. I currently don’t do that, and, without taking any measure, things will be good, on average, for most of my cacti.
On the other hand, I like to know about the natural habitat of my plants. Also, I’m interested on which kind of rocks and minerals they grow and which kinds I’m using. I’m aware that once the soil is inside a pot, it will not behave as it would do in nature, so it’s almost impossible to reproduce the soil of the habitat in a potted collection. Even knowing that, I’m still interested in the habitat. I use to search for images of a given species in its habitat, so I can have some clues about their natural environment, such whether the soils is sandy, humus-rich or a rocky outcrop. As much as possible, I would try to reproduce that, just for fun.
Finally, following other member’s experience, I’m more and more interested in grow my plants in soil-less, rocky substrates. When you start growing some cacti on pure mineral mixes, the kind of minerals that are being used gain new and higher importance. That’s why I’m here trying to objectively ask some questions about that (Ok, I know, I’m not being objective ).
So, how do you guys make a decision about adding limestone or calcareous rocks to the potting mix?
(a) I never add limestone and I avoid calcareous rocks
(b) I always add limestone and/or calcareous rocks
(c ) if the cactus is South-American, I don’t add limestone and avoid calcareous rocks; if the cactus is North-American, I add limestone and/or use calcareous rocks
(d) I search for information about the habitat and whenever is said that the soil is alkaline, I add limestone/calcareous rock
(e ) I don’t care
For example, I have a Mammillaria hutchisoniana, which is from Baja California. Finding information about Baja California soil can be tricky. At a first search, I found some references to soil alkalinity, but going a little deeper, I found out that the region is a mosaic of soils, and another Mammillaria species (phitauiana), also native to Baja California, likes acid soil because of the particular characteristics of its particular locality. As I don’t have any information about the exact locality for M. hutchisoniana, I can’t say for sure that it likes more alkaline soils. As a conclusion, I would get crazy if trying to find specific information for each species and try to give them these specific conditions. As result, I give up (option “a” above).
How do you guys usually deal with this?
Is there, somewhere, a list of cacti species with information about their locality and /or some information about it’s soil preferences?
This post is already too long, but I also would like to ask if calcareous rocks effectively will affect pH; in other words, should we bother about that or not?
In fact, I started this thread because I found a good and cheap source of ground dolomite, and I would like to use it in the sowing mix. Will it be a problem to Notocactus, and good for Thelocactus? Or it doesn’t matter at all?
here is a picture of the ground dolomite:
Thanks for your patience in reading all this, any comments are much welcomed.