Custom Cactus Soil Mix

Discuss repotting, soil, lighting, fertilizing, watering, etc. in this category.
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WayneByerly
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Location: In the north end of the Sequachee Valley, 65 miles north of Chattanooga Tennessee USA. Zone 7a

Re: Custom Cactus Soil Mix

Post by WayneByerly »

daiv wrote: Tue Feb 10, 2009 11:22 pm All Cacti are succulents, but not all succulents are Cacti
You know, you were one of the real significant influences on me, in my starting to collect/grow cacti. I saw your presentation on TV. It was brilliant ... just stinkin' BRILLIANT ... how could I NOT start growing cacti after having seen that? Thanks Daiv ... you have been at least partly responsible for my possessing one of the greatest loves of my life.

A general note to all the cactiphiles here. I know you are just as aware of this as I am, but I'm going to say it anyway. You MIGHT be surprised at how many people I've run into that were not aware of this little factoid: Despite the fact that cacti are xeric plants, it does not mean that ethey should be given a diet of very little water. They are PLANTS, and they WANT their water. They may SURVIVE on very little water, but they will not THRIVE.
Make the moral choice & always do what's right. Be a good example. Be part of the solution & make a contribution to society, or be part of the problem & end your life with nothing but regrets. Live a life you can be proud of! Zone 7a
overcrash
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Re: Custom Cactus Soil Mix

Post by overcrash »

What I've learned from trial & error is that there is no cactus soil recipe that can be used by everyone on this planet.
There are indeed general guidelines that one may follow like the good draining requirement. However when it comes to planting your cacti there are a lot of variables that count.
In my area, I am living in the southern part of Romania, Easter Europe, the climate is temperate or at least it used to be. Nowadays we have mild winters with -10C (instead of -20C) and very hot summers with 37+. So I have difficulties on choosing the right soil for my plants happy. In winter the soil should stay on the dry side however some moisture is needed for the roots as I don't give them water for at least 3 months because of the low temperatures - not -10C but 0C as I am keeping them in the greenhouse.
In summer the soil should retain moisture at least for a week or so.
Of course I can't keep the plants outside as the first months until July there is a lot of rain.
So starting from these conditions I made a soil recipe that fits almost all of my plants requirements:

- Pumice for good drainage - not the fine graded type
- Lava rocks, crushed, 1-3 mm size
- Zeolite - small sized
- Compost - the cheapest one I find or if possible collected by myself from the garden - it should not contain fertilizers because I want to control the nutrients; only 20% of the total
- Sand - collected from a location near me - it is a clay based sand with a lot if quartz - at least 30%
- Horticultural charcoal

So the soil is 50-50, it helps me control the moisture in summer and winter. This is the best combination that I used until now and the plants seem to enjoy.
As an advice for everyone, try to use ingredients that you can find in your area/ country. Don't use expensive ingredients, invest more in your plants. Try, try, try mixing them until you get it right.

With the hope that this post will help someone I salute you and wish you a very nice day!
Radu M
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ohugal
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Re:

Post by ohugal »

Loph wrote: Fri Feb 26, 2010 8:59 am if i may add a mix we have tested in hot ET coutnries.

this mix has had potted/tray plants survive through meter a day rains, 3months of straight rain, and all teh other suually hot sunny humid weather. i suspect this would be ideal in places like malaysia/thailand and neighbouring countries, also micronesia, central/south america and anywwhere else it stays warm and really humid. but there is no nutrition, so you must fertilize.

we use
pumice 10-20%
"fine" washed sand 20%
coarse washed sand (or small grit)40%
forget the name but it is basically sand from lava rock 10-20%
and add aa little bit of slow release ferts....be it pellet poop or chemical balls....we use poop.

this mix ahs grown plants in teh above rainy situations. the following species we have grown fairly succesfully in it, outdoors.

Astrophytum capricorne/ornatum/asterias, Acanthocereus, cereus, trichocereus, tenocereus, neobauxima (spelling?), Mammilaria decipiens/prolifera/many unidentified sp., hylocereus, selenicereus, harrisia just., Coryphantha elephantidens, Echinocereus viereckii, Echinopsis arachnacantha/various unknown hybrids, epiphylum (they they dont need it), various gymnocalycium speceis/hybrids, lophocereus schotii, myrtillocactus geometrizans and ubnknown hybrid, any opuntia (lol), thelocactus setspinus and some other stuff. all did quite well with little to no rotted plants.
I'm considering switching to a completely mineral soil mixture in the future for my cacti (with the expection of leafy species). Your recipe has ingredients which are readily accessible to me. In the second year after repotting, what is your watering regime? Do you add fertilizer to each watering? I have the following (water soluble) fertilizers suitable for cacti at the moment: 7:17:35 (with trace elements) and Peeter 20:20:20. I also have something called Vitanal (for cacti) (a liquid) with contains amino acids, vitamins, proteins and carbohydrates. It is not a fertilizer.
Location
Antwerp, Belgium
temperate, maritime climate with mild winters and cool summers
hardiness zone 8a
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westfork
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Location: IA/SD: USDA zone 4b/5a & heat zone 6/7.

Re: Custom Cactus Soil Mix

Post by westfork »

Thanks for the article and everyone's input on what soil works for them. As stated, we all have different climates, species, and care schedules so there is no one perfect cactus soil. After years of tinkering this basic mix works for us in the Upper Midwest with the pots pretty much left on their own except for winter. Drains quickly enough for periods of extended rain, enough moisture retention to go long periods between rain in high temperatures, some nutrient holding capacity, and heavy enough to sit tight in 60mph wind.

Previous mixes that had much fine rock and very coarse sand retained too much moisture for us. Found that an aggregate of fairly uniform size and not too angular was best to preserve air pockets between the pieces. Located sources of pea gravel with the right type and size of rock, and then used an old cooker pot to separate into two more uniform sizes - the smaller being 1/4" and a bit smaller (but no fines under 1/8") and the larger ranging from 1/4" to 3/8". These are used in different mixes depending upon the goals. Each 42 pound bag yielded about 26# of the small and 16# of the large.
sorting gravel
sorting gravel
M3IMG_4893 sm 8-26-2023.jpg (138.59 KiB) Viewed 1344 times
This shows the mix using the smaller gravel. Ideally the pumice would be the same size, but we buy in bulk and it is all 3/8". We used to use 50% or more pumice but thought it might stay too wet during long periods of heavy rain. This mix is:
pumice - 2 parts
1/4" gravel - 4 parts
hairy coir - 1 part (The more fibrous not pithy type)
potting soil - 1 part (Found Black Gold to hold up better than most)

Counting the mineral portion of this potting soil, the mix is almost 80% mineral by volume.
In this mix, the lower container showing the larger gravel is not used.
soil mix components
soil mix components
M3IMG_4898 sm 8-26-2023.jpg (160.75 KiB) Viewed 1344 times
Some time release fertilizer is mixed in depending upon the season. A pinch of Epsom salts for the coir. Occasionally use our tap water to supply calcium that the coir could bind.
Here is what it looks like freshly mixed. Some of the finer material is washed away through the pots over time.
cactus potting mix
cactus potting mix
M3IMG_4904 sm 8-26-2023.jpg (103.12 KiB) Viewed 1344 times
This is the mix that works well in our outside pots using the 3 9/16" x 4 1/2", .715 liter Anderson bands with mostly closed bottoms. The standard "bottom cross" bands cannot retain a gritty mix.

This is just another idea that could be useful to some and worthless to others, and is really just a small adjustment to the standard theme.
Iowa / South Dakota border area. USDA zone 4b/5a Heat zone 6-7
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MrXeric
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Re: Custom Cactus Soil Mix

Post by MrXeric »

westfork wrote: Sat Aug 26, 2023 8:42 pm Thanks for the article and everyone's input on what soil works for them. As stated, we all have different climates, species, and care schedules so there is no one perfect cactus soil. After years of tinkering this basic mix works for us in the Upper Midwest with the pots pretty much left on their own except for winter. Drains quickly enough for periods of extended rain, enough moisture retention to go long periods between rain in high temperatures, some nutrient holding capacity, and heavy enough to sit tight in 60mph wind.

Previous mixes that had much fine rock and very coarse sand retained too much moisture for us. Found that an aggregate of fairly uniform size and not too angular was best to preserve air pockets between the pieces. Located sources of pea gravel with the right type and size of rock, and then used an old cooker pot to separate into two more uniform sizes - the smaller being 1/4" and a bit smaller (but no fines under 1/8") and the larger ranging from 1/4" to 3/8". These are used in different mixes depending upon the goals. Each 42 pound bag yielded about 26# of the small and 16# of the large.
M3IMG_4893 sm 8-26-2023.jpg

This shows the mix using the smaller gravel. Ideally the pumice would be the same size, but we buy in bulk and it is all 3/8". We used to use 50% or more pumice but thought it might stay too wet during long periods of heavy rain. This mix is:
pumice - 2 parts
1/4" gravel - 4 parts
hairy coir - 1 part (The more fibrous not pithy type)
potting soil - 1 part (Found Black Gold to hold up better than most)

Counting the mineral portion of this potting soil, the mix is almost 80% mineral by volume.
In this mix, the lower container showing the larger gravel is not used.
M3IMG_4898 sm 8-26-2023.jpg

Some time release fertilizer is mixed in depending upon the season. A pinch of Epsom salts for the coir. Occasionally use our tap water to supply calcium that the coir could bind.
Here is what it looks like freshly mixed. Some of the finer material is washed away through the pots over time.
M3IMG_4904 sm 8-26-2023.jpg
This is the mix that works well in our outside pots using the 3 9/16" x 4 1/2", .715 liter Anderson bands with mostly closed bottoms. The standard "bottom cross" bands cannot retain a gritty mix.

This is just another idea that could be useful to some and worthless to others, and is really just a small adjustment to the standard theme.
I like your mix. That pea gravel especially. I've been using decomposed granite, but the stuff I buy from Home Depot is more sand than gravel and I end up not using a good deal of it. I'll see what my local stores have to offer.
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westfork
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Location: IA/SD: USDA zone 4b/5a & heat zone 6/7.

Re: Custom Cactus Soil Mix

Post by westfork »

MrXeric wrote: Sun Aug 27, 2023 5:41 am I like your mix. That pea gravel especially. I've been using decomposed granite, but the stuff I buy from Home Depot is more sand than gravel and I end up not using a good deal of it. I'll see what my local stores have to offer.
All the bagged pea gravel are different in size and composition. Even the same brand can vary greatly from lot to lot. We just check out the landscape department whenever in a big box store on trips to the city. Hate paying a dime per pound for rock, but much easier to work with than bulk. Over the last few years these are the three that came closest to what we were looking for:
Bagged pea gravel close to 1/4"
Bagged pea gravel close to 1/4"
M3IMG_4906 sm 8-27-2023.jpg (128.58 KiB) Viewed 1312 times
--In the center is what I used in the post above - the KolorScape from Bomgaars in Sioux City. The exact same product from their Cherokee location was way too large.
--To the right is the NorthRock from Lowes in Sioux City. Nice rock but small for my general potting mix. Very useful for a smaller aggregate though.
--To the left is the GreensMix from Lowes in Sioux Falls (Our two Lowes stock different brands). This was the closest size we could find until we discovered that second batch of KolorScape.
It is a bit larger than what we were looking for but workable. Almost didn't check this one out since many reviews said this was thumb sized or larger. Obviously batches vary a lot.

In the past we have used Cherry Stone chicken grit for the aggregate since I love all forms of Sioux Quartzite and it is plentiful and cheap here where it is quarried. But it is so sharp and angular that it packs too tight (and goes through tires). Home Depot is usually a good source for rock and aggregate, but around here they haven't had any pea gravel we liked. Same for Fleet Farm, Menards, etc.
Iowa / South Dakota border area. USDA zone 4b/5a Heat zone 6-7
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