Are you growing your cacti in a soilless mix?

[keith]

Strong Adsorption: Diatomite rock has strong adsorption and ion exchange functions. It can slowly transport silicon and be absorbed by plant roots, thereby growing plants healthily. It can be used as top dressing or soil amendments. "

Amazon disagrees with zero ion exchange ratio . Your book says to use bone meal high in Phosphorus I thought this forum said that was BAD. I don't know and have stopped talking about soil mixes especially on this forum. I read them , disagree with almost all of it and all I can say is whatever you choose to use it should drain well.

BTW I agree with most of what your book says buts its old and so am I

[ChaoticN]

Steve you mentioned 90 ppm of N causes bloat, is that for all species including jungle cactus plants? I was thinking a fast grower like a dragon fruit could handle more fertilizer than say a mamillaria.

Right now I’m feeding most of my jungle cactuses those granules I posted on here not long ago supplemented with gypsum granules for the calcium and they seem to like it.

Id also like to mention the mineral mix Steve recommended and the fertilization method he taught me is working great for most of my cactus plants with a few exceptions like cleistocactus or jungle types. I have found that for some tephrocactus the mineral mix can work really well with a small tweak, I added in 1/8” akadama with the pumice and DG.

[Steve Johnson]

Steve you mentioned 90 ppm of N causes bloat, is that for all species including jungle cactus plants? I was thinking a fast grower like a dragon fruit could handle more fertilizer than say a mamillaria.

My experience is confined to knowledge of desert cacti, and that's where I see nitrogen bloat as a problem among growers who pump up their desert cacti with too much N. For jungle cacti, higher-N feedings should be fine, although I'll leave the specifics to the people who grow them.

[MikeInOz]

Your book says to use bone meal high in Phosphorus I thought this forum said that was BAD. I don't know and have stopped talking about soil mixes especially on this forum. I read them , disagree with almost all of it and all I can say is whatever you choose to use it should drain well.

BTW I agree with most of what your book says buts its old and so am I

The Phosphorus in bone meal is only very slowly available. No problems with it even for P sensitive things. I am old too..

[ossy96]

Correct -- for jungle cacti like Christmas cacti, Thanksgiving cacti, etc., I think Jerry is on the right track. While a straight pumice-granite gravel mix is great for most desert cacti, I'll point out a few exceptions:

• Opuntioids (Tephrocactus for example)

• Echinopsis

• Eriosyce senilis

These cacti do need soil in the mix, in which case I'll recommend a 50% soil-50% mineral gravel mix. The only succulent I grow is a Haworthia attenuata, and it's also in a 50% soil-50% mineral gravel mix. My experience with succulents in general is close to zero, so I don't know if their roots would support a soilless mix without organic material.

I want to repot my echinopsis oxygona and some other cacti, in a few days, because of this i made some cactus soil with 20 % soil, 20% coconut coir, 30 % crushed red brick and tiles, 10 % river sand, 10 % perlite and 10 % seramis. Until now it was ok with soil from the garden, will it tolerate that much mineral percentage(60%)? My other cacti i will repot are astrophytum myriostigma and Mammillaria plumosa! Thanks

[Steve Johnson]

I want to repot my echinopsis oxygona and some other cacti, in a few days, because of this i made some cactus soil with 20 % soil, 20% coconut coir, 30 % crushed red brick and tiles, 10 % river sand, 10 % perlite and 10 % seramis. Until now it was ok with soil from the garden, will it tolerate that much mineral percentage(60%)? My other cacti i will repot are astrophytum myriostigma and Mammillaria plumosa!

From "The Cal-Mag of my dreams?" thread I started way back in July 2022, our horticulturalist-in-residence MikeInOz had a few things to say about coir:

I wouldn't use coir unless I absolutely had nothing else to use. And probably still wouldn't. It has many problems. 1, It is often high in chloride, this can be mitigated by rinsing several times. 2, It has very low S and Ca and very high K. So much so that it can cause Mg deficiencies unless it is amended. Soaking in CaSo4 or MgSo4 and CaNo3 after rinsing can help. 3, Orchid growers were initially told that Coconut was the medium to end the use of all other mediums and went ahead and used it at full throttle. What did they find? Most had great results for a start and then found all kinds of deficiencies showing up later, severe chlorosis, death of roots and death of the entire plant in many cases. 3, Fungal mycelium LOVES coir unless it is completely consumed by composting. It thrives in it and if it gets a foot hold, the entire root ball can become choked with white mold and dead roots. Fungus tends to proliferate in dry, acidic conditions rather than moist alkaline ones where bacteria usually dominates. 4, It should have Fe and Cu added to it. 5, It is sometimes prepared from green husks and can contain unwanted plant hormones. Having said all that some people say they have used it with success but I think we should be aware of it's possible problems. It is interesting to note that some commercial Dutch nurseries said they never want to have to see or deal with coir products again. If you want to use an organic component in your mix, a far superior product can be easily - if somewhat slowly - made a year in advance by using readily available products such and leaves, cow manure and sawdust or shredded garden clippings composted well and matured moist over a long time then dried, screened and stored for later use. Or if you have access to genuine cow manure (luckily I have from a farmer next door) you can age that and use it. Another option is to use a high quality composted pine bark as the organic fraction of your mix. All these are far superior in every way to coir.

But wait, there's more!

Coir dust is used successfully in mixes for bedding plants and general mixes where it is fed heavily (EC is high) and it is kept moist, but for mixes which dry completely you can have the troubles I mentioned. As long as the Ca, Mg, and S is balanced with it's high K, and the chloride is leached out it works ok. It actually has very good properties like high AFP and wettability. But because it is made from raw un-composted material, and some batches are exceptionally bad, when something goes wrong it goes wrong spectacularly. Another problem is that it holds water for such a long time, you might think your mix is dry and needs water when it doesn't. I cannot understand why cacti growers would use it.

Moral of the story: Stay away from coconut coir.

Regarding cactus mixes, keep it simple -- 2 or 3 ingredients for the mix. IMO anything beyond that is "over-engineering" the mix for no useful purpose. With that in mind, I think you'll do better with a simple mix containing soil and some sort of mineral gravel (pumice, Perlite, calcined clay granules or crushed granite poultry grit -- choose 1 mineral, not 2 or 3 or 4). If you can't get pumice, calcined clay granules (AKA Leca balls) are preferable over Perlite and granite gravel. The soil component coming from your garden is fine, but it must be sterilized first. Use a 50% soil-50% mineral gravel mix for Echinopsis, tilt more in favor of the mineral component for Astrophytum and Mammillaria.

[ossy96]

Thank you! Untill now i thought coir is the magic ingredient, and oh believe me every person i ask has such a different way to prepare the cactus soil, as i ask more people, the more comfused i am!

[Steve Johnson]

Thank you! Untill now i thought coir is the magic ingredient, and oh believe me every person i ask has such a different way to prepare the cactus soil, as i ask more people, the more comfused i am!

I know the feeling, and sadly a lot of confusion comes from gardening websites. Given Mike's many years of specialized knowledge growing cacti, it's a genuine blessing to have him on the forum.

[ossy96]

I want to repot my echinopsis oxygona and some other cacti, in a few days, because of this i made some cactus soil with 20 % soil, 20% coconut coir, 30 % crushed red brick and tiles, 10 % river sand, 10 % perlite and 10 % seramis. Until now it was ok with soil from the garden, will it tolerate that much mineral percentage(60%)? My other cacti i will repot are astrophytum myriostigma and Mammillaria plumosa!

From "The Cal-Mag of my dreams?" thread I started way back in July 2022, our horticulturalist-in-residence MikeInOz had a few things to say about coir:

I wouldn't use coir unless I absolutely had nothing else to use. And probably still wouldn't. It has many problems. 1, It is often high in chloride, this can be mitigated by rinsing several times. 2, It has very low S and Ca and very high K. So much so that it can cause Mg deficiencies unless it is amended. Soaking in CaSo4 or MgSo4 and CaNo3 after rinsing can help. 3, Orchid growers were initially told that Coconut was the medium to end the use of all other mediums and went ahead and used it at full throttle. What did they find? Most had great results for a start and then found all kinds of deficiencies showing up later, severe chlorosis, death of roots and death of the entire plant in many cases. 3, Fungal mycelium LOVES coir unless it is completely consumed by composting. It thrives in it and if it gets a foot hold, the entire root ball can become choked with white mold and dead roots. Fungus tends to proliferate in dry, acidic conditions rather than moist alkaline ones where bacteria usually dominates. 4, It should have Fe and Cu added to it. 5, It is sometimes prepared from green husks and can contain unwanted plant hormones. Having said all that some people say they have used it with success but I think we should be aware of it's possible problems. It is interesting to note that some commercial Dutch nurseries said they never want to have to see or deal with coir products again. If you want to use an organic component in your mix, a far superior product can be easily - if somewhat slowly - made a year in advance by using readily available products such and leaves, cow manure and sawdust or shredded garden clippings composted well and matured moist over a long time then dried, screened and stored for later use. Or if you have access to genuine cow manure (luckily I have from a farmer next door) you can age that and use it. Another option is to use a high quality composted pine bark as the organic fraction of your mix. All these are far superior in every way to coir.

But wait, there's more!

Coir dust is used successfully in mixes for bedding plants and general mixes where it is fed heavily (EC is high) and it is kept moist, but for mixes which dry completely you can have the troubles I mentioned. As long as the Ca, Mg, and S is balanced with it's high K, and the chloride is leached out it works ok. It actually has very good properties like high AFP and wettability. But because it is made from raw un-composted material, and some batches are exceptionally bad, when something goes wrong it goes wrong spectacularly. Another problem is that it holds water for such a long time, you might think your mix is dry and needs water when it doesn't. I cannot understand why cacti growers would use it.

Moral of the story: Stay away from coconut coir.

Regarding cactus mixes, keep it simple -- 2 or 3 ingredients for the mix. IMO anything beyond that is "over-engineering" the mix for no useful purpose. With that in mind, I think you'll do better with a simple mix containing soil and some sort of mineral gravel (pumice, Perlite, calcined clay granules or crushed granite poultry grit -- choose 1 mineral, not 2 or 3 or 4). If you can't get pumice, calcined clay granules (AKA Leca balls) are preferable over Perlite and granite gravel. The soil component coming from your garden is fine, but it must be sterilized first. Use a 50% soil-50% mineral gravel mix for Echinopsis, tilt more in favor of the mineral component for Astrophytum and Mammillaria.

Well pumice is not really available here and i dont really like perlite cause it floats... thats why i use the crushed red brick it is almost the same like clay granules just a bit sharper..

[Steve Johnson]

Well pumice is not really available here and i dont really like perlite cause it floats... thats why i use the crushed red brick it is almost the same like clay granules just a bit sharper.

Yes, indeed -- Perlite is the least preferable mineral because it's a floaty pain in the backside. If the crushed red brick has a certain amount of porosity, it'll be almost as good as calcined clay (not sure about pumice), in which case a 50% crushed brick-50% soil mix should still be fine for your Echinopsis. As I said earlier, keep it simple.

One other recommendation I'll make -- add a nice thick layer of nonporous gravel top dressing to the pot. Not only does it add a decorative touch, it also keeps floaty stuff from getting all over the base of your cacti when you water, and it prevents the upper part of the mix from drying out too quickly in summer. Although you don't want river sand for a mix, river gravel is good as a top dressing.

[ChaoticN]

Hey everyone it’s been a while since I’ve made a post here but I wanted to thank everyone for helping me figure out good mix’s for my cactus plants.

Hey Steve I wanted to thank you especially & I need to ask you another question, I have a few cactuses flowering right now and I was wondering should I still use the same fertilizer mix you taught me during flower? Using that mix u showed me has greened up my cactus plants quite a bit compared to what they looked like before, it has helped a lot with their appearance.

[Steve Johnson]

Hey Steve I wanted to thank you especially & I need to ask you another question, I have a few cactuses flowering right now and I was wondering should I still use the same fertilizer mix you taught me during flower? Using that mix u showed me has greened up my cactus plants quite a bit compared to what they looked like before, it has helped a lot with their appearance.

First of all, you're most welcome! Use the same fert regardless of whether cacti are or aren't in flower -- the belief that cacti need high-P fertilizers when they flower is a myth.