Is this okay for cactus soil

Discuss repotting, soil, lighting, fertilizing, watering, etc. in this category.
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Tuuumas
Posts: 7
Joined: Wed Apr 26, 2017 5:20 pm
Location: Finland

Is this okay for cactus soil

Post by Tuuumas »

So right now I have cacti in pure sand, which I'm told is a bad thing. So is it okay for me to just mix sand and normal plant dirt, as I don't have access to all these fancy vulcanic rocks they recommend here. I just want my cacti to be healthy. Also I've heard that the cactus mix they sell is not good either. Can I just do the dirt, or if not, what is the best (easyish) solution
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mmcavall
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Joined: Tue May 17, 2016 11:54 pm
Location: São Carlos - SP, Southeast Brazil, Cerrado Region

Re: Is this okay for cactus soil

Post by mmcavall »

Hi Tuuumas, what you describe is exactly the situation I had when entered the forum about a year ago. I had my cacti in a mix composed by 2 parts sand : 1 part dirt. It was very bad and I tried to improve it adding more and more sand... so it was getting worse... Reading the posts here and doing the tests described here: viewtopic.php?f=25&t=11498 I understood that sand is not a good ingredient.
I did not had access to "fancy" (lol) rocks such as pumice, perlite, cat litter and I had to find my own way. So that is the solution I've found (also reading the posts):
Any kind of gravel/grit is suitable. You can first try pure gravel/grit, and as you feel that something is missing to one or other plant, you can add a little dirt, leaf mold, coir, etc, but usually pure gravel/grit is sufficient.
I'm sure you can find some gravel around your location. Take a walk with a broom and dustpan and collect any kind of grit and gravel. Basaltic rocks are better than quartz. Reading "The Stone Eaters" issue on Xerophillia will help you, but, believe me, any pure grit you collect will be suitable.
Then use a sieve to discard the small particles, and wash all the rocks you will utilize, so the small particles and dusty will be washed out.
That's it. You have now a good mix basis. You can mix stones of different sizes. Many cacti species will do fine in this mix. I was not convinced at first, but my plants are telling me that it works. It is very cool to see health roots making their way among pure rocks.
If you feel that they need something more "fertile", just add a little dirt, or other ingredients, but remember that your mix must be aerated, so maybe only 20% of the mix will be dirt (it is just to give you an idea, but there is no exact recipe to follow).
With the time you will find your own recipe, but my advice is: start with any pure gravel, and forget the sand and the prepared cactus mix .
Tuuumas
Posts: 7
Joined: Wed Apr 26, 2017 5:20 pm
Location: Finland

Re: Is this okay for cactus soil

Post by Tuuumas »

Thank you for help
Salspi
Posts: 6
Joined: Fri Sep 01, 2017 11:00 pm

Re: Is this okay for cactus soil

Post by Salspi »

The mix I like to use is:

40% pumice 1/4" size
20% decomposed granite sand(not dust)
20% worm castings
20% coco coir

I fine sift the pumice and granite sand to make sure I get all dust out. This dust can accumulate at the bottom of your pot and create a sludge layer that will cause problems. I also add a 2" layer of lava rocks at the bottom of the pot for added draining before adding the soil on top of it. I don't know if this is optimal but it's how I do it and it works for me. I'm always looking for tips so anyone feel free to advise if there is an improvement that can be made. Hope this helps.
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ElieEstephane
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Joined: Tue Dec 13, 2016 12:10 am
Location: Lebanon (zone 11a)

Re: Is this okay for cactus soil

Post by ElieEstephane »

Tuuumas wrote:So right now I have cacti in pure sand, which I'm told is a bad thing. So is it okay for me to just mix sand and normal plant dirt, as I don't have access to all these fancy vulcanic rocks they recommend here. I just want my cacti to be healthy. Also I've heard that the cactus mix they sell is not good either. Can I just do the dirt, or if not, what is the best (easyish) solution
Hello tuuumas.
As mmcavall said u can use grit an gravel and all plants will do fine. However i'd watch out what kind of gravel i use. Stay away from alkaline rocks such as limestone and dolomite since south american cacti dont like them and will completely stop growing.
The thing i did when i started this hobby is i planted all my plants in 80% and 20% compost and placed them in full sun. I then watch how each plant grows and its rate of growth and change the potting mix and sun exposure accordingly. I found that full sun will completely halt growth on some species.
If you want to take it one step further, you can research the cacti you have and try to mimic the soil in their native environment. For example oreocereus species live in arid mountains in rubble with little to no humus or organic matter. From what i saw in other posts, oreocerei grown in high organic matter soil will grow small weak roots but growing them in pure mineral mix (grot and gravel) will force them to search for moisture and grow a stonger root system. Parodia\notocactus species on the other hand seem to like a little more organic matter in the mix. Epiphytes like even more organic matter in the mix.

In short, use a non alkaline gravel/grit mix with little to no organic matter and all your non epiphytic cacti will be happy.

Here's a picture of the mix i use.

Good luck!
There are more cacti in heaven and earth, Horatio, than are dreamt of in your philosophy.
One of the few cactus lovers in Lebanon (zone 11a) :mrgreen:
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