I've watched a couple YouTube videos about 511 potting mix which is 5 parts pine bark, 1 part perlite, and 1 part peat or soil. I may have been directed to those videos from a post on this forum. I don't remember.

Has anyone tried the 5-1-1 mix? What did you use it for, and what were the results?

Does anyone know if any type bark would work for this mix? I'd rather use local materials than pay for pine bark in a plastic bag. There's lots of elm bark available around here, and I have a chipper to grind it up. Any opinions about whether that would be as good or better than the pine product?

I have no experience with use to share...YET. I stumbled upon this 5,1,1 and have become intrigued with it. I ordered "1/4 inch Pine Bark Fines" by Bonsai Jack thru Amazon. I'll be mixing up my first batch today. I've no idea what to expect or how deep I'll play with his 5,1,1 home made soil. I intent to post more.
Tim

Always curious about pine bark fines but is this a thing to be mail-ordered? Have never seen at big box stores or local gardening stores.

You won't see pine bark fines at common stores.

I made my own bark fines. I made 3 dirt sifters with 1/8", 1/4", and 1/2" hardware cloth. The bagged pine bark was from Menards, which is like Home Depot or Lowes, but for Dakotans, Cheeseheads, and Minnesotans only. I didn't like the bagged product because it had lots of wood in it. I ended up using a lot of elm bark that I found in the woods, because that was pure bark. I ran the bark through my chipper, and then sifted it through my bark-gradation sifters. I think my final bark mix was 2 parts 1/8" plus - 1/4" minus and 1 part 1/4" plus- 1/2" minus. The YouTube videos I watched just used everything that passed through the 1/2" screen, and then discarded what went through the 1/8" screen. I didn't really like that product because it was too coarse.


I felt the 5-1-1 mix was a bit too airy for my needs. There was nothing in it that held any water. I added washed sand, crusher fines, topsoil, and locally-sourced sedge peat to my mix. I ended up with 5-1-1-.5-.5-.5 mix, and I liked that a lot better. If anyone's interested, I could post some pictures later, and my opinions on the benefits of this stuff. As of right now, the jury is still out. Seems like quite a bit of work, but in some instances it may be beneficial.

I know this is a s old . But howd it work out , Rubi ? What did you grow in it? I am considering it for sempervivums . The mix I currently use has been 75% pumice and 25% Coco Loco potting mix . I had some that didn't do too well due to the rains in summer this year. So I'm considering trying Pine bark in the mix as well. I am using my vacuum mulcher to make it the right size and it is a lot of work. I spent $90 on the motor. I probably would've been better off just blowing the money on bonsai jack pine bark fines. 🤣. But I figured I could use the leaf blower/mulcher. It's a tad awkward. And it is kinda heavy. I may return it and get a different one. I chose the Toro brand because it has a metal impeller.

Mcgilljen said: I know this is a s old . But howd it work out , Rubi ? What did you grow in it? I am considering it for sempervivums . The mix I currently use has been 75% pumice and 25% Coco Loco potting mix . I had some that didn't do too well due to the rains in summer this year. So I'm considering trying Pine bark in the mix as well. I am using my vacuum mulcher to make it the right size and it is a lot of work. I spent $90 on the motor. I probably would've been better off just blowing the money on bonsai jack pine bark fines. 🤣. But I figured I could use the leaf blower/mulcher. It's a tad awkward. And it is kinda heavy. I may return it and get a different one. I chose the Toro brand because it has a metal impeller.

I still use chipped and sifted bark for all kinds of stuff. I use it for bedding in my worm bins, I use it for mulch, and I do use it in potting mix. I didn't like the 5-1-1 ratio very much, but that would work for plants that like a virtually soilless mix. I'm gonna repot a Christmas cactus in something that's close to 5-1-1. I've got the bark soaking right now. We'll see how that turns out.

If you have questions about the 5:1:1 mix, I should be able to answer them. I started experimenting with container media in the 80s after I failed at bonsai, and the 2 mixes I came up with were the 5:1:1 mix and the gritty mix. It was hard at first, getting anyone to believe anything could be better than rich looking black compost in a pot, but it caught on and a lot of people are doing well in it.
5:1:1 mix



Gritty Mix:


Al

Al,
Could you post the recipes for your two mixes? I've seen so many modifications by others, I've lost track of the authentic Al's mixes--which really work well.
I've also lost track of your original lengthy and technical article about particle size and soil composition. As I recall, it explains why you don't add assorted smaller particle sized components. It took me awhile to read and digest, but totally changed what I look for in soil media.
Thanks

Before I jot down the recipes that serve as good starting points for the 5:1:1 and Gritty Mix, I'll explain a simple concept that will help those of you who build their own media and help others understand some things about what happens when we try to amend media we feel is too water retentive.

In order to take advantage of media that offer fast drainage and superior air porosity, it's essential that the the media are based on a very large % of coarse material. The reason for this centers on something called 'the threshold proportion'. The easiest way to explain how it works is by providing an example that can be 'seen' in the mind's eye. Start with a quart jar, half full of marbles. We can all 'see' the large pores between the marbles. Now, start adding peat/ coir/ sand/ other fine material (PCSO) to the jar. What happens? All the large pores between the marbles are beginning to become filled with PCSO. If we keep adding PCSO to the jar until there is exactly enough fine material to fill all the spaces between the marbles, we have arrived at 'the threshold proportion'. The threshold proportion is the most difficult proportion of media ingredients to grow in because the marbles reduce the amount of space available for root colonization and the only part of the medium available for roots to grow is in the PCSO; so, where the roots must grow, the level of aeration is the same as what it would be without the marbles, meaning the coarse material (marbles) has not contributed at all to aeration; and as we'll see in a moment, it has actually reduced o/a aeration on a per volume basis.

Let's do another experiment using the same ingredients. We have a jar filled with PCSO, and we know there is some air between the particles. We'll need to pretend that PCSO is fluid enough so when we drop a marble into the filled jar, a volume of PCSO equal to what the marble displaces overflows the rim of the jar. Start dropping in marbles. As each marble is dropped in, PCSO and the air between the particles is displaced, so with every marble dropped into the jar, o/a air porosity decreases. The same thing happens when we try to "amend" an overly water-retentive medium based on all or nearly all fine components. When you start adding coarse ingredients to water retentive media in hopes of increasing aeration, aeration actually decreases until we get beyond the threshold proportion, until there is no longer enough fine material to fill all the pores between the coarse ingredients; only then, does air porosity begin to notably increase.

The 5:1:1 mix works well for 2 main reasons. 1) If made correctly it holds only a small amount of excess (perched) water, which means the soil column is well aerated from the top of the soil column to nearly the bottom. 2) The use of pine bark and perlite work differently than adding perlite to fine ingredients. Perlite mixed with peat provides very little additional air porosity because the peat particles completely surround the perlite particles as the PCSO particles above surround the marbles. When perlite is mixed with the flat platelets of pine bark, one piece of perlite wedged between 2 flat pieces of pine bark provides a great deal or air porosity - imagine a BB wedged between 2 dimes to get a 'mind's eye visual'.

The Gritty Mix is screened to a size that ensures almost all water is held on the surface of soil particles, in the internal pores of porous ingredients (bark/ Turface MVP), and at the interface where soil particles contact each other. When combined, soil particles screened to a size that will not pass a 1/10" mesh cannot hold perched water, and perched water is the primary enemy of air porosity and root health.

5:1:1 Mix
5 parts pine bark screened so it passes through a 3/8 or 1/2" screen (fines included)
1 part sphagnum peat (chunks broken up - ok to include small sticks)
1 part coarse perlite
garden (dolomitic) lime (1-1/4 cups/ cu ft of soil or 1 tbsp per gallon of soil

Gritty Mix
1 part Turface MVP or Allsport (screen and use what doesn't pass aluminum insect screen)
1 part crushed granite (grower grit), or #2 Cherrystone/ quartzite, or Manna-Pro Poultry Grit
1 part pine bark screened 1/8-3/8" or fir bark screened 1/8-1/4"

FWIW - I have never grown a plant that didn't to exceedingly well when fertilized with Foliage-Pro 9-3-6. It has all nutrients essential to normal growth, including Ca, Mg, and all the micros; it derives >2/3 of it's nitrogen from nitrate sources and uses no urea (helps keep plants more compact and full); and, it comes in a ratio that closely matches that at which the average plant actually uses the nutrients (offers the grower greater control and allows the grower to fertilize at the lowest rate possible w/deficiencies or toxicities.

Al

I had trouble with the 5:1:1 in grow bags, there were spots in the center that were completely dry and had no roots. I wonder if it would be better in plastic pots?

The Christmas cactus I repotted with coarse bark similar to 5:1:1 is doing great. It seems to love it.

@tapla Is 5:1:1 your original invention? If so, you're famous. There are lots of people on YouTube that have stolen your idea.

I started talking about the 5:1:1 mix and The Gritty Mix in 2004 when I joined another forum site. Initially I failed or had poor luck at growing plants in containers because I had no understanding of the importance of air:water ratios in media. I set the plant's aside and started reading texts about soil science (before the internet), which provided the science that underpins their efficacy. Basically, I looked into what chunky materials would serve best as the primary fractions of container media. To keep it simple, I came up with pine bark, sphagnum peat moss, perlite, and dolomitic (garden) lime for the 5:1:1 mix at a 5:1:1 ratio with bark being the largest fraction, The gritty mix consists of equal measures of screened pine or fir bark, Turface MVP, and crushed granite or cherrystone in a 3/16" size. I do realize that both are used widely and sold commercially.
Initially, I had a hard time convincing anyone that these media would make growing in containers easier and more productive. Eventually though, people took note and more and more people started using the mixes. So, while I came up with the decision to combine certain ingredients and ratios of the basic recipes, other users eventually started referring to the mixes as 5:1:1 and gritty mix. In direct answer to your question, yes, I was the one who started talking about them and providing information about how water behaves in container media to hobby growers. I think that understanding how water behaves in container media, getting to a place where one needn't constantly battle their grow media for control of their plant's vitality, represents the single step forward a container gardener can make. The recipes simply provide basic ways to implement the concept, which is much more valuable than the recipes. From the point where our grow medium is working for us instead of working at cross purposes to our efforts, everything gets easier and the reward in terms of personal satisfaction become greater.

Al

WOW ! Thank you Rubi and Al for the kind and detailed replies! I apologize that I've not replied sooner . I have no notification system to tell me when someone replies to a question. So I don't see it unless I just stumble upon it somehow.

Rubi , I appreciate the update. It sounds like the bark is truly a good addition to soils that need aeration and some moisture too , but not wanting sogginess . Since I last posted , I've watched my sempervivums thrive in a concoction of around 6-7parts pumice , lava rock , chicken grit , perlite ( and other random mineral amendments I had laying around at the time ) and 3 parts Coco Loco and 3 parts bark . My exact ratios flew out the window as I struggled to fill all my troughs . The biggest bummer is getting the bark the right size . It kind of turns into a "mix til it feels right " game for me . I spend a fortune trying to make the best soils . I did recently notice from an experiment that the Coco Loco by itself dries quite well of put in one of the plastic troughs and wet down, then left to dry for a few days . I'm almost curious if it would dry faster than the mix with all the mineral amendments. I'm doing some experimenting now . I really need to get all my semps planted . Some are in nursery pots and root bound . Their peat chunks are hardened and I loath to take the time to remove the hard peat . So I may leave it on some . They're actually quite healthy despite their hard peat root prisons . I hate waiting for the roots to dry for a few days to repot too because they decline at first when I do that and take awhile to recover. I've killed some by doing that anyway. Plus , their chicks can root into the new soil I've made and carry on their legacy even if the mother died from the peat . What brand and type of chipper do you use for your bark ? I've been using a vacuum leaf mulcher and it's so slow ! Such a pain ! I want something faster . Haha !

Al , you're brilliant! I truly love the concept behind these mixes . I must admit that even though I research a lot when it comes to soil , I don't think I have as much patience as you have exhibited in finding all these answers. Your soil pictures look so gorgeous! I sure wish that pine bark fines were easier to come by . I have spent a sheer fortune recently buying pine bark mini nuggets, different brands of soil conditioners that are supposed to be made mainly of pine bark fines , topsoils that have pine bark fines , bagged Sandy loam , this , that , and the other . I do have turface MVP on hand . But I've had a strange issue in many plants that had turface in the mix . I used to mix 1 part pumice , 1 part turface, 1 part chicken grit and 1 part Coco Loco or coir together for my succulents. They grew compact and chubby and looked gorgeous for a year or so and then would suddenly decline . When I would pull them from their pots and look at the roots, they would be all brown and desiccated. Do you have any idea why this might be? Was it because I was filling in the air space between the particles? I didn't experience this in the pots without the turface. So something leads me to believe that the turface had something to do with dedicated roots . But many folks claim turface holds too much water. That doesn't really make much sense to me because I have watched turface get wet many times and be bone dry within a day. Do you think people say it holds more water when compared to pumice ? I have tried using your exact gritty mix recipe. But my plants dried out far too quickly when I did that. I am definitely one to underwater. I know that you grow sempervivums because I have seen your pictures on the same provide them forum . I love the tiny ones in the Chapstick lids . That is too cute. Do you think it is OK to use your Grittymix recipe and then add one part of potting mix? Or would the potting mix take away too much air space? I have actually observed what you were talking about regarding adding lots of mineral amendments to a fluffy potting soil. I have actually noticed that the plain potting soil sometimes seems to dry faster than the one with all the mineral amendments. I think I am understanding what you were saying regarding that . Your analogies make perfect sense . I've seen the marble experiments on YouTube actually. It's so interesting. Maybe some of my plants failed in pure gritty mix because I didn't fertilize. And because I'm a lazy waterer . Have you grown sempervivums in your 511 mix ? Did they do well ? I definitely want to lighten my semp mix because I am using 5 tier stands with plastic troughs. They're very heavy with my current mix. I worry that they will break the stands eventually. If the 511 mix would work well, I could just use it and not have to worry as much. I'm glad you mentioned the fertilizer you like. I will try that. The bark I'm able to get is full of sapwood. It's so time consuming picking it out . Is there any disadvantage to just leaving it in there ? And is there any very affordable way that you can recommend to get the bark to the correct size ? I bought a bag of Happy Frog Soil Conditioner today. It seems to have bark that's 1/4" to dust size . Would that be good for 511 mix ?

Again, thanks to both of you for taking time to reply to me! I am honored that both of you replied

@Mcgilljen Lol - Thanks for the kind words. Having answers sort of comes with 40+ years of exploring different ways of making a plant's root system happy, as that IS a prerequisite if the plant is to be healthy.

Try these operations for pine bark. Let them know you're making your own grow medium and the bark needs to be dust to less than 1/2". If you draw a blank, ask if they can make a recommendation. Last week I found a perfect bark product in Austin TX, with minimal effort, for someone who had been searching for years ..... just by nosing around the internet and making a couple of calls.

Seagle Landscaping
1774 New Era Rd
(865) 428-1888

Mountaineer Mowing & Mulching
(865) 270-0870

When I would pull them from their pots and look at the roots, they would be all brown and desiccated. Do you have any idea why this might be? Was it because I was filling in the air space between the particles? If you didn't screen out the fines over insect screen, that's likely the reason - too much water. I screen the Turface and screen the dust out of the cherrystone or crushed granite and the prescreened fir bark I use. I then keep the volume of bark at 1/3 of the mix, but +/- the ratio of grit to Turface to alter water retention. Examples:

Std mix is
3 parts screened pine or fir bark
3 parts screened Turface MVP
3 parts screened crushed granite (grower size) or 3 parts #2 cherrystone (quartzite)

For more water retention:
3 parts screened pine or fir bark
4 parts screened Turface MVP
2 parts screened crushed granite (grower size) or 3 parts #2 cherrystone (quartzite)

For less water retention:
3 parts screened pine or fir bark
2 parts screened Turface MVP
4 parts screened crushed granite (grower size) or 3 parts #2 cherrystone (quartzite)
And even more subtle alterations are equally as easy.

The key takeaway here is you can markedly increase water retention if necessary without having to depend on perched water as the reservoir. When you screen the particles so they're larger than about 1/10", all the spaces between soil particles remain water-free. Increasing the volume of particles with internal porosity (Turface), and decreasing the volume of particles that hold water only in the surface of the particle offers wide latitude. That adjustability sets the stage for very healthy root systems for a very large variety of plants.


.... many folks claim Turface holds too much water The word "Turface" is on the bag of many products of varying sizes, all of which are inappropriate for use in container media except for Turface MVP and The screened Turface product Profile sells specifically for use in media (hard to find). Turface MVP, even if screened over insect screen and the fines are used elsewhere, is too water-retentive to be used as as a 1-part medium. It's purpose as it relates to the gritty mix is no more than adding water-retention w/o need to sacrifice aeration. You'll find that, in every case, anyone who complains that Turface holds too much water doesn't understand the concept that a medium's particle size primarily drives water retention, and the answer to too much water retention (associated with Turface MVP) is to use less of it, not discount it entirely as a part of your grow media.

Do you think it is OK to use your Gritty mix recipe and then add one part of potting mix? I wouldn't bother - I'd just use another mix: Reason, Turface takes more effort to make than most mixes and it cost's more on a per volume basis; so, it doesn't make sense to invest the time and $ it takes to make the mix and then undo it's most important characteristic - excellent aeration from top of the soil column to the bottom of the soil column, no matter what the ht of the soil column. In all honesty, if there was a plant that needed more water retention than I could manage by taking advantage of the medium's adjustability, I'd switch to the 5:1:1 mix. It would be pretty much the same as growing in a gritty mix amended with potting soil for less effort and less $ outlay.

Do you think people say it holds more water when compared to pumice? Yes, and they would be right. The internal pores of Turface products are open, so water and air can move freely in and out of the pores. Internal pores of pumice are closed at least to the degree that pumice from some sources can float on water for years before becoming waterlogged. This means that most of the air porosity pumice adds to media is the result of fracturing of the outer walls of pores on the particles' surface.

I've seen the marble experiments on YouTube actually. It's so interesting. Would you be kind enough to let me know what searchwords you used to find it or provide a link. I'd like to listen to whoever did the video.

Maybe some of my plants failed in pure gritty mix because I didn't fertilize. Oh goodness. Yes. Using a mix that drains that freely requires close attention to nutritional supplementation. And because I'm a lazy waterer. That too. While the gritty mix's ability to hold water is often underestimated, watering on an as needed basis is pretty much a standard part of any care regimen.

Have you grown sempervivums in your 511 mix? Yes Did they do well? Yes - you can see some bark if you look closely.

Semps will grow almost anywhere and will be at home in very spare (low nutrient load) media. In fact, they really often don't need a medium at all.




I'm glad you mentioned the fertilizer you like. I will try that. I mention it often because it's a product that delivers at least as much as it promises. It is the best product I have ever used for containerized plants, and the reasons are many and varied.

The bark I'm able to get is full of sapwood. Is there any disadvantage to just leaving it in there? And is there any very affordable way that you can recommend to get the bark to the correct size? There are several disadvantages to having a lot of sapwood in the bark. 1) It immobilizes nitrogen because it breaks down much faster. 2) It's breakdown is associated with a pH upward spike at some point during the composting process 3) While it might not seem important, work done by soil biota produces exothermic heat, which can warm the soil up to 10* higher than it normally would be, This isn't an issue for houseplants, but can be an issue for plants grown outdoors.

I've always had ready availability and easy access to pine bark of appropriate size. Some people have used mower or a small wood chopper to break it down, but I think you can find something if you devote a little time to searching the net and making calls.

I bought a bag of Happy Frog Soil Conditioner today. It seems to have bark that's 1/4" to dust size. Would that be good for 511 mix? If you were using in in the place of the peat fraction - yes. If you're using it as the base of the mix - no ...... you might as well just use the medium as it is. Mixing the bottom 6" of grow medium in any pot with an equal measure of perlite will reduce the amount of excess water the planting can hold by half. Adding some form of ballast can additionally limit how much excess water a planting can hold.
Compare D to A below to see how an overturned pot can work passively to eliminate a significant fraction of the excess water a planting can hold. Even tipping the pot (compare B to A) after a thorough watering can make a difference you can see the moment you tip the pot (after it has stopped draining).


Al

I'm excited to see Al posting here, as I discovered and have been reading so many old posts on other sites about soil and Al's gritty and 511 mixes. What an education, thank you!!

I want to try the 511 mix for the first time on some indoor potted ficus trees. I have a couple questions after reading the recipe above and the older discussions on other sites.

The bark: does this need to be partially composted or not? I'm having trouble finding bark with nothing else added, except for UniGrow fine orchid bark. That looks like it may be the right size but isn't partially composted.

Do I need to mix this up and wait 2 weeks before I repot my plants into it?

Thank you, I'm a newbie and appreciate the help! Also, I live in the LA area, I wouldn't think it would be so hard to find the bark component….

Thanks for the kind words, Tina!
The bark: does this need to be partially composted or not? No. It used tio be commonplace to find packaged bark that had been high in wind rows and turned with heavy machinery several times before it was packaged, but all the bark produced now is sold as fast as it can be skinned from the trees and milled. I've given up on even looking for it. The biggest issue with uncomposted bark is nitrogen immobilization, but that is a fairly minor concern due to the fact that conifer bark has natural polymers (suberin/ lignin) that limit the bark's rate of decomposition. That means populations of the soil biota that immobilize nitrogen are naturally controlled by the fact the natural polymers limit their ability to break down the bark for the energy to multiply. All you need to combat the minor immobilization is the knowledge it exists and making sure you fertilize regularly - but not with a fertilizer that derives it's nutrients from organic soil amendments. I'm having trouble finding bark with nothing else added, except for UniGrow fine orchid bark. That looks like it may be the right size but isn't partially composted. Pine bark of appropriate size is in short supply because most of it is contracted to manufacturing operations who heat the bark to high temps in specialized furnaces and burn the gasses created. If you're looking for a small quantity to see how well 5:1:1 works, you can find pine bark at American Bonsai: https://www.americanbonsai.com... - but you're better off looking for a local source from a financial perspective.

Bark is acidic and dolomitic lime is basic. It takes about 2 weeks If the mix is moist) for the reaction phase to be completed. After the reaction phase comes the residual phase, during which the calcium and magnesium in the lime will be more readily available. I have often made the mix and potted plants in it on the same day without discernible issue, but you should try to wait the 2 weeks if you're growing food plants susceptible to BER as a greater number than normal of the first fruits are very likely to be affected. The worst that would happen with your ficus is, you might notice a few leaves that are abnormally shaped of have holes/tears in them as they unfurl or soon after. That is temporal and might not even occur as the top growth will be largely suspended (by the plant) until the plant's chemical messengers signal plant central that the root system is now robust enough to support more top growth.

You might make a call to Shasta Forest Products in Yreka, not because I think they package pine bark, but because they might know who does in CA. Also, I'm sure you have wholesale greenhouse/ nursery ops in the area that supply soil components to those ops which still make their own media. I have a fallback supplier like that (about 50 miles distant) I can always depend on if I can't find it locally, but I have always had good luck finding nearer sources.

I helped a friend in the SF area for several years with her citrus and figs. She used to buy her bark from a place called Orchard Hardware Supply or something close to that name. Does that ring a bell? It's been a few years, but prolly still worth a call.
Al

tapla said:In order to take advantage of media that offer fast drainage and superior air porosity, it's essential that the the media are based on a very large % of coarse material. The reason for this centers on something called 'the threshold proportion'. The easiest way to explain how it works is by providing an example that can be 'seen' in the mind's eye. Start with a quart jar, half full of marbles. We can all 'see' the large pores between the marbles. Now, start adding peat/ coir/ sand/ other fine material (PCSO) to the jar. What happens? All the large pores between the marbles are beginning to become filled with PCSO. If we keep adding PCSO to the jar until there is exactly enough fine material to fill all the spaces between the marbles, we have arrived at 'the threshold proportion'. The threshold proportion is the most difficult proportion of media ingredients to grow in because the marbles reduce the amount of space available for root colonization and the only part of the medium available for roots to grow is in the PCSO; so, where the roots must grow, the level of aeration is the same as what it would be without the marbles, meaning the coarse material (marbles) has not contributed at all to aeration; and as we'll see in a moment, it has actually reduced o/a aeration on a per volume basis.

Al, do you have any specific number estimate for the percentage of a soil mix that would need to be fine particles to run into the PCSO problem you mention? Obviously your mixes attempt to minimize the PCSO percentage to well under 10% of the mix, probably approaching 1%. But there is a lot of runway between your formulas and a typical commercial potting mix, which appears to be 90% PCSO and therefore very problematic by your standards.

If you had a mix with maybe 10% sand that is too small in particle size and around 10% bark fines, is that 20% fines going to be too high? I realize that it would raise the perched water table a bit.

Mcgilljen said: Maybe some of my plants failed in pure gritty mix because I didn't fertilize. And because I'm a lazy waterer . Have you grown sempervivums in your 511 mix ? Did they do well ? I definitely want to lighten my semp mix because I am using 5 tier stands with plastic troughs. They're very heavy with my current mix. I worry that they will break the stands eventually. If the 511 mix would work well, I could just use it and not have to worry as much. I'm glad you mentioned the fertilizer you like. I will try that. The bark I'm able to get is full of sapwood. It's so time consuming picking it out . Is there any disadvantage to just leaving it in there ? And is there any very affordable way that you can recommend to get the bark to the correct size ? I bought a bag of Happy Frog Soil Conditioner today. It seems to have bark that's 1/4" to dust size . Would that be good for 511 mix ?

The trick with gritty mix and succulents is to put the plants into the shade and give them about three months in an unstressed environment to root. Once you see more vigorous plant growth you can bring them out into the sun and they will acclimate. Putting them into heat stress when they are freshly planted into gritty mix can be too much.

Do you filter your Turface MVP to get rid of the fines? Perhaps you left too many fines in the mix, and that is why your plants developed problems.

Those of you trying to find a good grit for Al's gritty mix can use the following very cost-effective method:

1) Find a wholesale garden supplier who stocks Olympia #2 sand. This is sand with both coarse and fine components, but most importantly it is well-washed sand. It is a gorgeous color and the lack of dust really saves time.

2) Run that washed sand through a sieve that is 1/12th of an inch, and the grit that does not pass is what you can use in the gritty mix. Even filtering to 1/20th of an inch gives a grit that is FAR superior to any horticultural sand you can buy in a bag.

Olympia #2 sand can be purchased under $150 per cubic yard so you can get quite a lot of it cost-effectively. I lose about 50% of the volume filtering it. The left side of this photo is what you retain with a 1/20th of an inch sieve. The right side of this photo is what you retain with a 1/12th of an inch sieve. Al's theoretical ideal is 1/10th of an inch.

tapla said: It used tio be commonplace to find packaged bark that had been high in wind rows and turned with heavy machinery several times before it was packaged, but all the bark produced now is sold as fast as it can be skinned from the trees and milled. I've given up on even looking for it. The biggest issue with uncomposted bark is nitrogen immobilization, but that is a fairly minor concern due to the fact that conifer bark has natural polymers (suberin/ lignin) that limit the bark's rate of decomposition. That means populations of the soil biota that immobilize nitrogen are naturally controlled by the fact the natural polymers limit their ability to break down the bark for the energy to multiply. All you need to combat the minor immobilization is the knowledge it exists and making sure you fertilize regularly - but not with a fertilizer that derives it's nutrients from organic soil amendments.

I have noticed that plants will often do well for the first 12 to 18 months in 511 mix and then start to suffer. I wonder if this is the inevitable breakdown of the bark robbing nitrogen? Is it possible to compensate for this by over-adding some time release fertilizer to the surface of the container, and are there any guidelines about how much to add, using something like Osmocote as a reference?