Are you growing your cacti in a soilless mix?

Discuss repotting, soil, lighting, fertilizing, watering, etc. in this category.
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Steve Johnson
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Are you growing your cacti in a soilless mix?

Post by Steve Johnson »

If not, you may want to consider going soilless. I just found a good article on the subject which I'd like to share with our members:

https://southsideplants.com/blogs/plant ... otting-mix

There's only one caveat -- the article mentions coir as an ingredient. Avoid it like the plague. If you'd like to know why, our resident horticulturalist MikeInOz will give you the details:

viewtopic.php?p=398697#p398697

I went soilless back in 2012 when I moved 64 of my 68 cacti from a heavy soil-based mix to a hydroponic pumice and granite gravel mix. The benefits have been quite significant, although there may be a couple of drawbacks to this mix for some of you:
  • Pumice is easily available in the US, but not so easy in other countries. If you can't buy pumice, Perlite is second-best. Only problem there is that it floats away whenever you water. A good thick layer of gravel top dressing on your pots keeps the floaty stuff from getting all over your plants. Another viable option -- calcined clay cat litter. Either Perlite or calcined clay will work just fine as the mineral component in a soilless mix.
  • The hydroponic approach is appropriate to humid or very humid climates. If your local climate is on the dry or very dry end of the scale, such a mix will dry out too quickly in the pot -- that's when you'll need a soil substitute for better water retention as the soilless mix dries out like it would in a soil-based mix.
If you're able to grow your cacti in a hydroponic mix, the only downside is the fact that you'll have to fertilize every time you water them in the growing season. If you'd rather not fertilize every single time, a hydroponic approach is by no means your only choice for going soilless.

A helpful repotting hint

Actually, this is standard practice among experienced growers, and it applies regardless of whether you're switching to a soilless mix or staying with your soil-based mix of choice...
  • Step 1 -- take the cactus out of its pot and inspect the roots. If you see a root mealy infestation, follow step 3 on what to do.
  • Step 2 -- clean the old soil out of the roots as thoroughly as possible. That includes digging up into the root ball to dislodge the soil -- important because a bolus of old soil hiding under the base will be asking for trouble if you leave it in the pot.
  • Step 3 -- if you do have a root mealy infestation, soak the roots in a 2% solution of soap and warm water for about 1/2 hour (insecticidal soap is best). Soap residue gives you some extra protection when they dry out, so don't rinse them before you repot.
  • Step 4 -- always repot your plants in fresh dry mix.
And finally -- if you're repotting cacti in the growing season, let the roots settle in for 2 weeks, then water the plant. For you new growers out there, following these steps will give your cacti a good start on life under your care.

Happy growing, everyone! :)

Steve
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Download
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Re: Are you growing your cacti in a soilless mix?

Post by Download »

I've moved to a semi-hydroponic mix last spring (September-October last year), and have been using a mixture of about 60% decomposed granite, 20% sea-shell based chicken grit (people have misunderstood me when I have previously mentioned this, thinking it's chicken shells or something, but it's actually calcium-rich grit that chickens eat to improve digestion) and 20% orchid mix (mostly decomposed bark - orchid mix here in Australia does not contain peat), which is then sieved with a ~0.8mm (35 mesh?) sieve to remove the fines.

I made a big mistake though: I did not use enough fertiliser. Because it wasn't a true hydroponic mix, I was a bit lax with fertilising, and then we had an unusually wet spring which probably washed a lot away. Then on the first really hot day (~40 degC) a bunch of my really well established plants, that had been exposed to this sort of sun many times before, suddenly got "burnt".

I use quotation marks because it's not really like normal sunburn. Instead of burning and then the burns bits "shrinking", with well defined edges between burnt and unburnt, most of the burnt plants developed leathery brown/yellow patches that fade into normal flesh (similar to corking, but not the same). It's very unusual burning.

Anyway, as these were established, sun-hardened plants, and the only thing I had changed since last summer was the growing medium, I could only conclude that nutrient deficiency caused the problem. So I quite aggressively fertilised all my plants and have not seen the problem since despite several similarly hot days.

So yeah, use fertiliser every watering.
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Steve Johnson
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Re: Are you growing your cacti in a soilless mix?

Post by Steve Johnson »

Download wrote: Sun Feb 12, 2023 5:46 amSo yeah, use fertiliser every watering.
Have you thought about going with the Osmocote slow-release Cacti & Succulents fert MikeInOz uses? That would certainly make things easier for you. Why Osmocote makes it only in and for Australia is beyond me. All we get out of Scotts here in the US is Miracle-Gro Succulent Plant Food -- it's a miracle if anyone can grow cacti or succulents with that stuff.
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Re: Are you growing your cacti in a soilless mix?

Post by FredBW »

What are the true benefits of a soil less mix? Soil-based pathogens?
I have been keeping Cacti for years in Cactus mix without pathogens,and for the most part they thrive.
Most all of my problems have been from watering issues. If I go soil less,am I still not going to have watering issues?
And as far as Coir,I have my own cactus mix that has some coir in it that is working very well. I also have 2 San Pedro cuttings in 100% coir doing exceptionally well. I have to disagree with avoiding it like the plague.
If I switch to a "soil less" mix am I not introducing myself to a whole new ballgame of problems?

Keeping cacti in soil and fertilizing 2 or 3 times a year during growing season. Repotting every few years with a hand full of worm castings, seems simple,cost effective,and without much danger of screwing up. Everywhere I read talks about how cacti are not heavy feeders,so what is the benefit?
Yes,if you love to tinker soil less cacti growing might have it's rewards. But as plumbers say. The more bends you put in a pipe,the more likely you are to have a clog. So for the average cacti grower like me,why would I go soil less? Sorry,I don't get it.
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ohugal
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Re: Are you growing your cacti in a soilless mix?

Post by ohugal »

FredBW wrote: Sun Feb 12, 2023 2:35 pm So for the average cacti grower like me,why would I go soil less? Sorry,I don't get it.
Have you fully followed the conversations from the last months or so? Because growing in a soilless medium (no or very low amount of peat for example) is more forgiving towards overwatering. You mentioned most of your problems come from overwatering as I understand it.
I don't think a soilless mix is applicable to every species, but I think Steve's collection of cacti is a good candidate. It's also a question of understanding and embracing different cultivation practices. If you have watering issues with certain plants why not try a different approach?
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Steve Johnson
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Re: Are you growing your cacti in a soilless mix?

Post by Steve Johnson »

Fred, I'm just giving people different choices to consider. If what you're doing works for you, fine. However, this brings up a question -- are your cacti growing as well as they could be? The only way to get the answer -- try growing a few cacti in a soilless mix for comparison and see if their growing quality improves over the course of 2 years. This is not about "tinkering", it's all about testing to see what works best and what doesn't in terms of giving our cacti the optimal conditions for excellent, vigorous growth over the course of many years.

I'm not trying to convince you to test some of your cacti on a soilless mix, and I do realize that you may be taking chances you're not willing to take. That's entirely up to you, and if you're satisfied with the way your cacti are growing, continue whatever you're doing.
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FredBW
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Re: Are you growing your cacti in a soilless mix?

Post by FredBW »

I have been following the conversations over the last months with great interest. Which is what led me to what I posted.
A person new to growing Cacti reads all of this and is tempted to go all out. When in reality growing in soil works extremely well with very little attention or maintenance..
The watering problems I have had are not enough to do all of this. The problems I have really aren't that many. I am not trying to belittle all the work that is gone into fertilizers and advanced growing.
But I am trying to point out this is "advanced" and for an average cactus grower it might be a bit over the top.
I am trying to say it in a way as to not ruffle any feathers which isn't easy. I certainly don't mean to step on anyone's toes.
But I think I am pretty successful growing in soil without all that much work,and will leave it at that.
I probably should have stayed out of it. But the horse is out of the barn ,and I will say no more :)
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Re: Are you growing your cacti in a soilless mix?

Post by Steve Johnson »

FredBW wrote: Sun Feb 12, 2023 10:09 pmI probably should have stayed out of it. But the horse is out of the barn ,and I will say no more :)
Among other things, the forum is there to share knowledge, information, and opinions. There's no one right or wrong way to grow cacti that works for everyone in the world. There's certainly nothing wrong with being an "average" grower either.

For whatever it's worth, I'm relaying my personal experience to help other growers who might benefit from it...
ohugal wrote: Sun Feb 12, 2023 7:40 pmI don't think a soilless mix is applicable to every species, but I think Steve's collection of cacti is a good candidate.
Exactly, and I'll give you an example of the difference between tinkering and testing:
  • Tinkering = throwing things up against the wall to see what sticks (figuratively speaking), no thought behind why changes may or may not lead to better results.
  • Testing = clearly identifying problems, and coming up with thoughtful solutions based on experience.
Sometimes testing has to be a matter of trial and error by the grower observing changes that are good, bad, or indifferent. In the pre-Internet days, the only way to go from beginner to expert was by killing lots of cacti in the process. Back then if you had a local expert to guide you when you entered the hobby, the trial-and-error process wouldn't be so painful. Unfortunately there were no local experts around when I fell in love with cacti at the tender age of 12 in 1970. I spent the next 20 years going through trial and error (mostly error) as a tinkerer without knowing why I was having so many problems. What I'm doing now is light years ahead of what I was doing before circumstances forced me out of the hobby in 1991 -- thanks entirely to what I started learning when I built a new collection in 2011 and joined the forum that November.

Here's the "custom" mix I got when I purchased my first round of cacti from the California Cactus Center in June 2011:

CCC_soil_sample.JPG
CCC_soil_sample.JPG (123.25 KiB) Viewed 27569 times
The owners of the CCC recommended that I lean out the mix with pumice, but only for some species. By the end of 2011, I instinctively knew that most (if not all) of the cacti wouldn't do well in their mix. Getting opinions from various forum members in early 2012 led me to a recommendation from Darryl Craig of CoronaCactus Nursery -- go with a soilless pumice and granite gravel mix. Once I took all of my cacti out of the CCC mix, I was shocked by the poor root systems coming out of the pots. At that point I wasn't tinkering, I was testing. And because I was being guided by an expert grower, the trial-and-error process was almost painless, ending the 2012 growing season with results that were better than I could've imagined. However, I say "almost" because there were a couple of cacti that didn't do well in the hydroponic mix...

Tephrocactus articulatus papyracanthus from the CCC -- unpotted after a year of being in pumice and granite gravel mix (3/16/13):

Tephrocactus_articulatus_var_papyracanthus_Jr03162013.jpg
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Tephros grow taproots only if they're grown from seed, but their preferred method of propagation is by dropping segments that root. Whenever you buy Tephros, you'll most probably be getting rooted segments like the "paper spine" cactus you're seeing. Problem: No taproot, and those thin scraggly fibrous roots wouldn't support growing in a soilless mix hydroponic or otherwise. Solution: When I moved it to a 50/50 mix with pumice and soil from the CCC, the "paper spine" finally started growing new segments because the roots were growing too. That experience came directly from another member who suggested it.

Another Tephro which I got from the CCC in 2012 -- articulatus inermis on 5/26/12, and unpotted on 3/17/13:

Tephrocactus_articulatus_var_inermis05262012-03172013.jpg
Tephrocactus_articulatus_var_inermis05262012-03172013.jpg (133.09 KiB) Viewed 27569 times
Also a rooted segment, although the "pine cone" cactus didn't mind being in a hydroponic mix. With that said, it has been doing a lot better once I moved it into the same 50/50 pumice and soil mix I used for the "paper spine". The only other cacti that needed soil in the mix for better growth -- 2 Eriosyce senilis, and experience coming from the same member who suggested it for the Tephros.

Truth be told, I only have direct experience growing 66 species, all of them desert cacti, so I can't tell you about other desert species that really need soil in the mix. If you're already an experienced grower doing well with a soil-based mix, more power to you. For good or ill, everything starts out in the roots -- if you're inexperienced and/or you're having problems with your cacti, chances are good that a soil-based mix is the cause of your trouble.

Not sure if you should go soilless? When in doubt, ask for advice on the forum and more widely-experienced members than me can help.
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CactiJim
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Re: Are you growing your cacti in a soilless mix?

Post by CactiJim »

Do you guys think that growing cacti in Phoenix, Arizona would do well with a soiless mix? Or does the extreme aridness and heat during summer warrant perhaps a 25% organic/75%inorganic mix? I mainly use terracota and plastic (that Terracota thread about the hawarthias really got me thinking, Steve!) but I’m very curious about testing an inorganic mix and maybe watering more frequently and fertilizing the inorganic pots every time I water.

Man, I want to buy like 12 of the same cactus species of a similar size and run a test with all different types of soils to see which one does the best. So much exploration, so little time!

-Jimmy
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Tom in Tucson
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Re: Are you growing your cacti in a soilless mix?

Post by Tom in Tucson »

CactiJim wrote: Tue Jun 27, 2023 6:49 am Do you guys think that growing cacti in Phoenix, Arizona would do well with a soiless mix? Or does the extreme aridness and heat during summer warrant perhaps a 25% organic/75%inorganic mix? I mainly use terracota and plastic (that Terracota thread about the hawarthias really got me thinking, Steve!) but I’m very curious about testing an inorganic mix and maybe watering more frequently and fertilizing the inorganic pots every time I water.

Man, I want to buy like 12 of the same cactus species of a similar size and run a test with all different types of soils to see which one does the best. So much exploration, so little time!

-Jimmy
I use a nearly 100% inorganic mix. The 1-2% organic material is either blown in by the wind, dead animal exoskeletons, or scant fragments from my various mineral sources. I've used no deliberate organic soil in over 8 years, and I have no noticeable growth limitations thus far.
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Re: Are you growing your cacti in a soilless mix?

Post by Steve Johnson »

CactiJim wrote: Tue Jun 27, 2023 6:49 amMan, I want to buy like 12 of the same cactus species of a similar size and run a test with all different types of soils to see which one does the best. So much exploration, so little time!
I know the feeling.

Since Tom in Tucson is doing well with a largely inorganic mix, it makes a good argument in favor of the idea that such mixes work even in an arid climate. Given the rather high humidity in my part of L.A., straight pumice takes too long to dry out, and I found that granite gravel in the mix is a good "moderator" as the mix goes from wet to bone-dry in about 7 or 8 days. Because pumice retains a surprising amount of moisture, straight pumice may actually be good for growers in places like Arizona, New Mexico, etc. This is something you'll have to test for yourself:
  • Fill a nonporous pot with pumice and weight it dry. Write down the weight.
  • Water the pot until water comes out the drain hole like a faucet. Weigh and write down the saturated weight.
  • Weigh the pot every day until the pumice reaches its dry weight. Write down how many days it takes for the pumice to go from wet to bone-dry.
Desert cacti love it when their roots dry out between waterings in the growing season. The question is -- how often should they be watered? I water most of my cacti every 2 weeks in the growing season, so I figure on a week of the roots soaking up the water and a week of going dry, and that's my wet-dry cycle. If the straight pumice wet-to-dry test works out for you, you'll have a good idea about how often you should water. What we're talking about here is an essentially hydroponic approach, the requirement being that you'll have to fertilize every time you water.

The only caveat I make regarding soil-less mixes is the fact that some species' root systems won't grow well in them, as I noted in one of my posts from February 12. That'll be the post involving photos of my Tephros. But for a lot of desert species, I highly recommend going soil-less/hydroponic whenever possible.
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Re: Are you growing your cacti in a soilless mix?

Post by CactiJim »

I will try this for sure.

Generally, is there a rule of thumb for the maximum time allowable for soil to be wet? Say, bone dry, a pot and substrate weigh 1lb. Fully wet, 1.5lb. And it takes 5 days for the pot and substrate to weight 1lb again. Is 5 days too long or about right? I know variables such as species and season affect this but just generally.

Took me a while to respond because my AC broke but I finally fixed it.
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Tom in Tucson
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Re: Are you growing your cacti in a soilless mix?

Post by Tom in Tucson »

CactiJim wrote: Tue Jul 11, 2023 6:14 pm I will try this for sure.

Generally, is there a rule of thumb for the maximum time allowable for soil to be wet? Say, bone dry, a pot and substrate weigh 1lb. Fully wet, 1.5lb. And it takes 5 days for the pot and substrate to weight 1lb again. Is 5 days too long or about right? I know variables such as species and season affect this but just generally.

Took me a while to respond because my AC broke but I finally fixed it.
Congratulations on fixing your AC. That must have been a nightmare. Many years ago I lived in Glendale AZ, and the AC went bad in June. The quickest repair took almost 2 weeks.

Anyway, back to the topic, Even with a 100% mineral mix the main 2 factors effecting soil drying are particle size, and exposure to the sun. Clear as mud?
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Re: Are you growing your cacti in a soilless mix?

Post by Steve Johnson »

CactiJim wrote: Tue Jul 11, 2023 6:14 pmGenerally, is there a rule of thumb for the maximum time allowable for soil to be wet? Say, bone dry, a pot and substrate weigh 1lb. Fully wet, 1.5lb. And it takes 5 days for the pot and substrate to weight 1lb again. Is 5 days too long or about right? I know variables such as species and season affect this but just generally.
I don't know if there's a hard-and-fast rule on the matter, although I'd say that a cactus mix going from wet to bone dry in 5 days is acceptable. Then it becomes a matter of how often we should water, and it really depends on the species. No easy answers on that one, but a few basic criteria may be helpful:
  • Springtime growers vs. summertime growers vs. cactus species that grow during the spring and summer. Cacti that do most of their growing in summer will need water more often than they do in spring. For example -- Turbinicarpus (with the exception of valdezianus) blow up like beach balls and split if they're watered too often in spring. I water my Turbs every 3-4 weeks in spring, then every 2 weeks when they put on their summertime growth. Turb valdezianus does most of its growing in spring (watering every 2 weeks), doesn't do much in summer (watering every 3 weeks), and puts on some fall growth. While the rest of my cacti are done with deep watering for the year, the valdezianus gets one last drench.
  • Plump vs. "thirsty". Some species should stay plump all throughout spring and summer, while other species do better if you let them get a bit shriveled between waterings. If your powers of observation are good -- and you learn more about the behavior of the cacti you're growing, you'll know which is which.
  • Plant size. I'll give you another example, this one involving an Astrophytum myriostigma I got back in 2011. I used to water it every 2 weeks in spring and summer. Then as it got bigger (and bigger and bigger), I started noticing that the base was getting awfully shriveled with that summertime watering schedule. The plant gets watering every 10 days in summer, which I started doing a few years ago.
It takes some time to develop a feel for how often we should be watering our cacti, and a "conservative" approach beats killing them with kindness when they get watered too often. The good news is that your cacti won't die of dehydration unless you let them go without water for a year.
Tom in Tucson wrote: Tue Jul 11, 2023 7:59 pmEven with a 100% mineral mix the main 2 factors effecting soil drying are particle size, and exposure to the sun.
Sorry, but I'll have to disagree with you on that...

The primary factor drying out the potting medium should be roots soaking up the water. If the root system is properly sized to the pot (in other words, not overpotted) and the potting medium supports robust, healthy root growth, evaporation is only a minor secondary factor.

If growers living in arid climates are relying on low-fired terracotta pots to dry out the mix, then A. they're using the wrong mix, and B. porous clay causes all kinds of problems in terms of root growth. I'll explain why and what you can do about it here:

viewtopic.php?t=45833

Tom -- I'm not making any assumptions about whether you do or don't grow your plants in terracotta, so this is just a general FYI to our members living in arid lands.
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Re: Are you growing your cacti in a soilless mix?

Post by CactiJim »

Tom in Tucson wrote: Tue Jul 11, 2023 7:59 pm
CactiJim wrote: Tue Jul 11, 2023 6:14 pm I will try this for sure.

Generally, is there a rule of thumb for the maximum time allowable for soil to be wet? Say, bone dry, a pot and substrate weigh 1lb. Fully wet, 1.5lb. And it takes 5 days for the pot and substrate to weight 1lb again. Is 5 days too long or about right? I know variables such as species and season affect this but just generally.

Took me a while to respond because my AC broke but I finally fixed it.
Congratulations on fixing your AC. That must have been a nightmare. Many years ago I lived in Glendale AZ, and the AC went bad in June. The quickest repair took almost 2 weeks.

Anyway, back to the topic, Even with a 100% mineral mix the main 2 factors effecting soil drying are particle size, and exposure to the sun. Clear as mud?
Yeah, it was brutal. It was over 100° everyday and it was broken for a week and a half. Wife was very frustrated (rightfully so! :? )

I’m still experimenting with my soil mixture and with porous vs non-porous.

I recently got a bunch of soil amendments but here is what I have:

-Top Soil Plus (by E.B. Stone Naturals) https://www.summerwindsnursery.com/az/p ... mendments/

-Nature’s Way Lava Sand https://www.summerwindsnursery.com/az/p ... mendments/

-3/16 pumice https://www.ofwolfinbargerinc.com/mixing-components/

-(3/16)/(3/8) lava cinders/rock https://www.ofwolfinbargerinc.com/mixing-components/

-3/8″ Palm Springs Gold (just gravel/rock) https://www.ofwolfinbargerinc.com/decorative-rock/

You're probably familiar with this Tom but I also have a bag of Tank's cactus mix (basically coconut chips (3/8 size) and pumice https://www.amazon.com/Tanks-Pro-Organi ... 9902&psc=1

I think I'm gonna try what you're doing Steve. Straight up pumice and gravel (Palm Springs Gold), in my case, with glazed pots/sealed terra-cotta pots.

I know this is quite a number of soil amendments but I really like experimenting. Interesting because I recently repotted some golden barrel seeds and the roots on those things - WOW. Pretty sure that was either 50% pumice and 50% worm casting or 75% pumice 25% worm castings. That soil seemed to have done really good. Again, I'm just here experimenting and stuff, nothing too crazy.
-Jimmy, Phoenix, AZ
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