A cactus mix idea part 2 (oh, no!)

[Steve Johnson]

Okay, I've been researching this a little more, and I'd like to give another try at coming up with my own cactus mix. For those of you hardy souls who haven't become exhausted of this whole thing, I'd like to propose some ideas.

First, I'll see what I can do about going for a mineral soil without any organic components. The cactus mix at the California Cactus Center just doesn't seem to be doing it for me, so I think I'll have to find a source for sandy loam without any organics -- no peat, no compost, no nothing. Second, I have 3 other ingredients that'll mix with the loam by ratio for my various cacti. This gives me 3 different mixes according to my collection:

For my Cephalocereus senilis and Melocactus matanzus - 30% sandy loam, 50% pumice, 10% crushed granite, 10% decomposed granite
For my Astrophytums and Turbs - 40% sandy loam, 40% pumice, 10% crushed granite, 10% decomposed granite
For the rest of my cacti - 50% sandy loam, 30% pumice, 10% crushed granite, 10% decomposed granite

Fergit Lowe's and Home Depot. For that matter, Armstrong Garden Centers are useless for any advice besides how to kill your C&S. There's only one halfway knowledgeable nursery left that I know of in my area. It's not because they have any expertise about cacti, but I can talk to them about what I need to find. Whatever they don't already have, they can get for me, and it has always been a stand-out place for going the extra mile. We used to see this kind of place a lot more.

I realize that there are so many different variables it would be impossible to come up with the "perfect" cactus mix. What I'm trying to figure out is a good educated guess based on the cacti I have in my collection and in my area. If anyone would be kind enough to give me some feedback, I'd appreciate any thoughts and/or recommendations.

One last thing -- after some further reflection, I think it's apparent that fertilizer has to be part of the equation. A. Dean Stock posted on the MSU fertilizer which he recommended, and it seems to be a better fit for cacti than the fertilizer I was steered to when I first got my collection. If you'd like to check it out for yourself, here's where you can find it:

http://www.repotme.com/orchid-fertilize ... index.html

Thanks!

Steve

[iann]

Try to avoid mixing together aggregates of different sizes. All that does is let the smaller particles fill up the gaps between the larger ones. Obviously your sandy loam is going to fill up a lot of gaps anyway, but if they are mostly filled already by mixing a fine granite with a coarse granite then you just get a solid mass.

You can still use the dense packed soil, but it completely saturates when you add water and that is risky to plants. You can also compensate by adding less soil to get back some air spaces, but you can end up with so little soil that you might as well not have bothered.

So simplest to stick with your loam plus a single graded aggregate, maybe two. I add some (graded) grit with my clay granules because the mix is extremely light otherwise. Also it lets me add a limestone grit to some plants and still keep the soil mix consistent across the collection. In my greenhouse if a pot is too heavy compared to the others, it will never get watered and I'm likely to keep tipping it out to see why it won't dry out

[cactushobbyman]

In my greenhouse, I keep it simple. One part chicken grit, one part perlite, one part course sand, one part diatomaceous earth, and one part screened super soil. Fertilizer I use time release Osmocote. I have used this fertilizer since the 80'S. Great stuff. Knew the owner when they first went into business. Received a lot for free.

[*Barracuda_52*]

Up here in the woods we are limited to good supplies when it comes to stuff for soil mixes and also due to i have many diffrent types plants, i mix up my own potting soils for the diffrent plants i make due with what i can get. The stuff in bags from the stores i always have to clean it, take out any fert beads, mix it with several other ingrediants to get it right for my needs, nuke it and go from there.. I like using alot of pumice but thats hard to come by here have to order that so most the time i have to use perlite which has stinkin fert in it so i presoak it for few days wash it and then soak it again for another day and wash it again to get rid of any fert in it. I have sand everywhere up here but i preffer to use a calcium/grit sand thats for pet birds that i get cheap. Theres alot of things i can use to add to my soil mixes to get them adjusted just right. Graded/crushed lava, charcoal, shreded bark, coco coir and so on, but the coir i mainly use for my frogs tanks as i dont care to use it in my soil mixes.
Everyone has there own prefferances when it comes to soil mixes for plants what works for one person might not work for another.

[Steve Johnson]

Today I spoke at some length with an arborist at Sunset Nursery in Silverlake. This lady has been around for quite awhile, and she really knows her stuff when it comes to plant soils. Yeah, I know -- an arborist? But she was pretty good on cactus soils too, so she comiserated with my problem when I tried to find a mineral soil mix with very little to no organic materials. The arborist confirmed what I suspected. Retail nurseries simply do not have a pure (that is, inorganic) sandy loam, so all they have available are commercial mixes. The sad reality is that c&s comprise a very small percentage of the retail plant business in general. Yes, a few cactus mixes here and there may be adequate, but most go from bad to awful, and there's no retail demand for specialist cactus mixes worthy of the name. Want loam? Fine, but you're looking for bulk quantities, which would be completely out of reach unless a specialist nursery can justify doing it in bulk and at their price. However, we still have a problem there -- as Ian will tell you, loams currently available in the U.S. are very inconsistent in quality, and the vast majority of loams are too high in clay content to be useful as ingredients for c&s mixes.

This brings me back to square one with the CCC. I spoke with them Tuesday, and they were kind enough to tell me about what's in their mix. Basically, sandy loam, pumice, and fir bark as the only organic component. The mix has 20% of the organic, so I thought it seemed awfully high. Then today I went to California Nursery Specialties (aka the "Cactus Ranch") in Reseda. The owner has been doing it for at least as long as the CCC, and he was happy to spend some time on the phone with me about his mix. Turns out that it has some different organic materials, and even higher overall percentage than the CCC's mix. So the CCC's mix has the lowest amount of organic material, and the best I'll find compared to any of the other c&s mixes available in the greater L.A. area.

In terms of true specialty mixes, I suppose CCC would rate only as "adequate." However, when we consider all the other so-called c&s mixes at Home Depot, Armstrong Garden Ceters, etc., I think the CCC starts looking pretty dang good. The pumice will have to be upped a lot more. And I'll have to factor in different ratios according to the species I'm dealing with. But there's a lot I can work with, so this is just a matter of learning more and hopefully getting better at the art involved with cultivation. I withdraw my previous criticisms of the CCC's cactus mix (the fertilizer thing is another matter, though).

However, I'm not completely giving up on a couple other ideas -- a long shot, but possible. First, the Huntington Botanical Garden has a horticulturalist of many years specializing in their desert collection. Someone at the Huntington said that he makes up his own custom mixes in bulk amount, but he will occasionally provide excess amounts. I'll contact him to find out A. if someone like me could get into that when it's available, and B. what he might have in a mix that could be better than anything I'd be able to find from even the best retail nursery. Second, the L.A. Arboretum holds c&s sales a few times a year. Perhaps a specialist or two there could have their own custom mix batches large enough that a smaller batch can be found. Once again, this would depend on whether or not their mix is any better than what I already get at the CCC. Although these possibilities aren't workable for anyone living too far away, perhaps some of you in the general area may get some use out of the ideas I'm proposing.

By the way, does anyone have thoughts about adding some crushed gravel to pumice? I'm thinking about adding a little more weight to my pots in case they could use some extra stability in the high winds we sometimes get. Hasn't happened so far, but the vast majority of my pots are 3" - 5", and I don't want them going over a second-floor porch for a crash.

Thanks for all the time I keep taking up here -- hope you get something out of it!

[CoronaCactus]

You could substitute the pumice for crushed granite #5, which is about the same size chuncks as pumice, it's cheaper too. The rest of the mix would be for water retention. Personally, i'd chose one or the other. I've used both but see no reason to anymore.

or

Substitute the sand for DG (the sandy, finer stuff, not too chunky) this definetely adds weight to the pots. A flat of DG/pumice pots is twice to 3 times the weight of a pumice/supersoil flat. DG has pretty much all the trace elements needed, which in turn allows you to be less picky about which fertilizer to use.


BTW, if you're a CSSA member or a member of a local SoCal affilliate club, the HBG Desert Forum is held each year in January and admission is free.

[Steve Johnson]

You could substitute the pumice for crushed granite #5, which is about the same size chuncks as pumice, it's cheaper too. The rest of the mix would be for water retention. Personally, i'd chose one or the other. I've used both but see no reason to anymore.

or

Substitute the sand for DG (the sandy, finer stuff, not too chunky) this definetely adds weight to the pots. A flat of DG/pumice pots is twice to 3 times the weight of a pumice/supersoil flat. DG has pretty much all the trace elements needed, which in turn allows you to be less picky about which fertilizer to use.


BTW, if you're a CSSA member or a member of a local SoCal affilliate club, the HBG Desert Forum is held each year in January and admission is free.

Well, I do like the idea of DG. The closest source I can find in my area is Bourget Bros. in Santa Monica, but they only have it in 60 lb. bags. The small size of my collection keeps me to more limited amounts of what I can handle, so I'll look around to see if I may be able to find a place that has the finer grade of DG you're talking about. If that doesn't work out, #5 gravel might be more doable.

The CCC's cactus mix doesn't have all that much pumice, so I think the pumice I was planning to add would be substituted for #5 gravel just fine. After finally settling on the custom mix that seems the best fit for me, I'm finding these ratios: 60/40 pumice to CCC cactus mix for most of my cacti, 70/30 pumice to cactus mix for the Astrophytums, Turbs, C. senilis, and Melo matanzus. If I use the #5 gravel instead (yes, I'd rather have that stability!), I think that I may need to skew the ratio a little in favor of the cactus mix. Maybe more like 50/50 and 60/40, since gravel does lose the porosity one would have with pumice. That being the case, I'd appreciate any ideas you have. I understand there's no way that someone else can ask me for any kind of precision. However, I'm glad for whatever advice that comes from the people who are willing to give it.

EDIT -- I just found DG at La Canada Rustic Stone in Pasadena. They sell finer grades, and by the shovelful is no problem, so a 20 lb bag would suit me just fine. (Oddly enough, now I know that #5 gravel is the thing I can't find anywhere.) This changes the equation, since I'll have to figure out the proper balance between DG and pumice. On the one hand, too much DG will (I think) turn it into concrete, and on the other too much pumice won't let water hold long enough for the roots to get any moisture. Also, I've been using terra cotta pots. If my soil is DG and pumice, I'm concerned that in summer the pots would dry out long before my cacti have the chance for getting any moisture at all. Our summer heat is generally low 80s during the day, but with the occasional heat wave. Our part of L.A. is normally a good 5-10 degrees cooler than downtown or the San Gabriel/San Fernando valleys. Please bear in mind that I water only in the evenings. Under a worst-case scenario, I'm sure moisture would be retained over at least a night in terra cotta. Is that sufficient for the moisture needs of cacti, or would plastic pots be better?

Now I'm excited by the possibility of DG, especially being away from any organic materials. I'd really appreciate any help on advice for what is now "unknown territory" on my part.

By the way, there's a c&s society in the San Fernando valley that meets once a month on Sundays. Used to be a member back in the early 70s, so I think it would be great to rekindle the enjoyment I had with that when I was a lad. If I can make it, what a nice way to start 2012!

Thanks so much, Darryl. And merry Christmas to everyone on the forum!

Steve

[jenni]

Why dont you keep it simple then and just grow in straight pumice. Lots of growers do that around LA and it seems to work great. You just have to water and fertalize a little more IMO.

[Steve Johnson]

Why dont you keep it simple then and just grow in straight pumice. Lots of growers do that around LA and it seems to work great. You just have to water and fertalize a little more IMO.

Unfortunately, my collection is on the porch of my apartment over a 2-car garage. Here's what the exposure looks like when we get high winds in the area:

My pots are mostly 3" - 5", so all pumice is asking for a bunch of cacti to go crashing down. (When those 40 mph gusts came through on the 1st, I was very lucky that I didn't lose anything. With DG it's better safe than sorry.)