Container Soil Questions

AndrewRaz(5-6)October 13, 2013

First of all, thank you all for your wisdom here. I've read through a large amount of the material here, and it has been enlightening to say the least. I know Al ("the" Al) is the mastermind behind the gritty and 5-1-1 mixes, but so many people have been able to take what he has put together and run with it. So thank you all, and especially you, Al (From MI, just a short hike from Detroit, where I'm going to school, no less!).

I think I understand the concept behind the mixes for the most part. I might not have all the nuances, and definitely not the lived experience though (reading isn't doing). I'd love to pick your brains on a couple lingering questions, Al or any of the other experts here about both the gritty and 5-1-1 mixes:

1). How does one determine criteria for substituting components? Al said something about "sacrificing plant vitality on the altar of convenience." I go to school, and I can't always feasibly take my plants with me on break, and with all my courses, I don't always have enough time to fiddle as much as I might like, so if I need soil that doesn't have to be watered as frequently, how do I determine what to substitute, and how much?

2). What do I do with components that don't pass the sift? Granite, Turface, bark, etc. What do I do with it if it's too big or small? "Waste not, want not," right? What do I do with granite, turface, bark, etc, that may be either too big or to small for use in the container?

3). How exact do I need to be in sifting? I imagine if I spent the time, I could sift until every single piece of crushed granite (Manna Pro poultry grit) passed through the 1/8" screen, and have none of it retained at all. Do I just give it a couple shakes, or what?
3b). What about bark--some of it can easily pass through a mesh of a certain size, but still be 4 times as long as it is wide. Just cut/break it, or what?

4). What is sapwood? How important is it to remove? Is it identifiable by color as all light wood, or is there something more to it?

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A...lots of questions to answer....sifting gets rid of the small elements of a potting mix that prevents good drainage (an important factor). Sapwood is the stringy pulp-like wood particles that break down much quicker than bark. If you are able to find quality components to work should not have a great deal of waste when sifting. Gritty mix appears to be the fastest draining....most work/maintenance intense mix. It requires constant watering/feeding (especially in warm weather). You can tweek all mixes to be more draining or perch more water. Hope this quick synopsis helps a bit. Experiment.....

    Bookmark   October 14, 2013 at 11:10AM
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Ohiofem(6a Ohio)

Andrew: What plants are you wanting to put in one of these mixes? What conditions will they be living in? (Indoors? Southern or northern exposure? How often can you water?) If you're growing an indoor bonsai in a small container, you're going to need to give it a lot more attention than a ficus in a 5-gallon pot in low light. The bonsai needs a gritty mix that has been made to the strictest standards, while the larger plant may not require a mix that has been so carefully sifted.
I have many house plants in gritty mix and several in 5-1-1. In the winter in my centrally heated house with low sun, my larger plants don't really need to be watered that often. When hot summer comes to the Ohio River Valley, I need to water more often.

    Bookmark   October 14, 2013 at 8:33PM
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Thank you both for your responses.

Ohiofem: I'll list the plants I have (some of which I will give away) with the intended potting medium I plan to use. Right now, I have a couple sanseveria (gritty), a few ficus cuttings (probably 511), a gardenia (511) and an azalea 'bonsai' (511). I also have a juniper and a Japanese Maple outside that are just about dead (lots of factors). The windows in my room face south, and I do get quite a bit of direct light. The azalea says it isn't supposed to be in temps lower than 60F, and it has been fluctuating wildly, so I brought it inside. It is also the most problematic--an online purchase with a near-solid mass of soil of two different consistencies around the outside vs in the root ball. Hence the need to repot it.

I *can* water most days, but I must to be able to leave them for a few days at a time, or leave them with a neighbor - I don't always have a lot of control over my schedule.

That's why I'm asking about the conditions of modifying the mixes. I will probably stick with the recommended recipes, but I would like to understand more behind it. I think I get the general concept now, mostly, but I just don't know how to go about considering "alternates" if need arises. I just threw some soil together before I knew anything for the sanseveria, and it ended up a peaty mess that is either wet for days or dry and doesn't take water again. Because I didn't know what I was doing, the JM and the juniper mix ended up being an even mix of bark, peat, and soil, and it just stays wet for days (part, but not all of the reason they aren't doing well.) If I want to lengthen the time between required waterings, do I just add more peat, or some other component? How much, and then how do I know how much to offset the PH? I know that would increase the PWT, but that's kind of what I'm trying to get at with my question.

I know sifting removes the fines that clog up the drainage. But once I sift those out, what do I do with them? Can I use particles of granite, turface, perlite, or bark that are too large or too small for anything else? That's also why I want to know how particular I need to be about particulates.

    Bookmark   October 14, 2013 at 10:49PM
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Ohiofem(6a Ohio)


I think people new to these mixes always overestimate how quickly they dry out and scare themselves about how often they will have to water. Most inexperienced growers water too often as it is. I have many large plants growing in gritty mix inside during the winter that can go two or three weeks between waterings. Even my most demanding plants in smaller containers of gritty don't usually need to be watered more than once or twice a week. And, I find the 5-1-1 needs about the same amount of watering that the better quality store bought mixes I’ve used in the past--like Promix and Fafards--do.

You have a pretty large and varied plant collection that ranges from the sanseveria, which I have found impossible to kill, to the azalea "bonsai," which I don't think anyone but a bonsai master could keep alive indoors over the winter. (I did keep one alive for one fall and winter by carrying it from microclimate to microclimate inside and out, sometimes twice a day. Not worth it.) And maintaining a Japanese maple or juniper over winter is a different kettle of fish. But, I’ll throw in my 2 cents on maintaining houseplants over the winter in Michigan in hopes that someone else will add theirs.

On your specific questions:

1. Substitution: The size of the components is the most important consideration. For gritty mix, you want all ingredients between about 1/8 inch and 3/8 inch in diameter. For 5-1-1, you want all ingredients at 3/8 inch or smaller. Secondly, I wouldn't try to substitute for the pine/fir bark in either mix. The gritty mix is one-third bark and the 5-1-1 is 70 % bark, and I think that is the most important ingredient in both mixes. In gritty mix, you can substitute an inert substance that is not absorbent for the granite, and one that holds some water for the Turface. Perlite would do for either, although it is closer to Turface in its behavior because it does hold a lot of water on its surface. If you want the gritty mix to hold a little more water, it would be better to increase the Turface or floor dry and reduce the grit than to use ingredients smaller than 1/8 inch. Used indoors, I don't think you want the 5-1-1 to be any more water retentive than it already is. When I use 5-1-1 outdoors for summer vegetables, I substitute Turface or NAPA floor dry for the perlite and substitute compost for some of the peat to increase its water holding capability.

2. What do you do with the screened out material? I add the stuff I sift out of gritty mix to my 5-1-1, or I add it to my outside beds.

3. Personally, I don't spend anywhere near the amount time and effort many others use on screening materials for the gritty mix. And I don't screen materials for the 5-1-1 at all. I just rinse the dust off the granite grit and only rapidly sift the Turface and bark over insect screen for the gritty mix. If I were growing more picky plants or bonsai in very small containers, I would spend a lot more effort on this. (I would use 5-1-1 for your gardenia and azalea since they both like moister soil.) Most of my plants are in one-gallon pots or larger, so I don't worry about it.

4. Sapwood comes from the wood under the bark of the tree and is fairly easy to spot if you have a good source of pine bark. It usually is a lighter color and can be easily splintered into straight pieces, unlike bark chips which are hard to break up. Just take out the obvious stuff. If your bark has up to about 5 percent sapwood mixed in, it will be OK.

    Bookmark   October 16, 2013 at 6:19PM
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Thank you so much, Ohiofem! Your answers were very helpful.
As you can tell, reading doesn't answer all the questions. I'm one of those people that would bug people a little more and get some more answers rather than charge ahead and screw something up. So thank you again for your answers.
P.S. I don't have high hopes for the Azalea. But without new soil, I think there's no hope for it at all.

    Bookmark   October 18, 2013 at 2:36PM
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seysonn(8a WA/HZ 1)

I think that you have to understand the concept.

You cannot just concentrate on drainage and aeration. The other side of the coin is moisture retention and with comes nutrients storage.

The other issues are : Indoor vs outdoor, Annual vs perennial. Plant types. That s some plants don't mind slightly wet soil and in fact some plants like that. Then others cannot tolerate too much moisture. Then there are differences in climates and growing conditions.Then also there is a practicality issue that require us to compromise. So you have to juggle all those balls the best you can. Gardening is not a pure science.

So putting all those together, I will have my own little recipe for 5 .1.1 mix. I am gardening at PNW. If I were gardening in south Texas I would do differently.

    Bookmark   November 11, 2013 at 4:14AM
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Ohiofem(6a Ohio)

I would encourage those just starting out with making their own potting mixes who are willing to put in the effort to follow Al's recipes as closely as possible the first time. After that, you can consider minor variations depending on your own experience. Drainage and aeration are in fact the most important considerations. If those are close to ideal, moisture retention is taken care of and nutrient use only requires careful attention to using the proper fertilizers in the proper amount on a regular schedule.

Hundreds, if not thousands, of people have used Al's recipes with excellent results since they were first discussed on Gardeweb eight years ago. Many others think they know enough to make significant alterations in the recipes even though they have never given the real thing a chance. They are often disappointed.

Here are the recipes with Al's comments:

The 5:1:1 mix:

5 parts pine bark fines, dust - 3/8 (size is important
1 part sphagnum peat (not reed or sedge peat please)
1-2 parts perlite (coarse, if you can get it)
garden lime (or gypsum in some cases)
controlled release fertilizer (if preferred)

Big batch:
2-3 cu ft pine bark fines
5 gallons peat
5 gallons perlite
2 cups dolomitic (garden) lime (or gypsum in some cases)
2 cups CRF (if preferred)

Small batch:
3 gallons pine bark
1/2 gallon peat
1/2 gallon perlite
4 tbsp lime (or gypsum in some cases)
1/4 cup CRF (if preferred)

I have seen advice that some highly organic (practically speaking - almost all container soils are highly organic) container soils are productive for up to 5 years or more. I disagree and will explain why if there is interest. Even if you were to substitute fir bark for pine bark in this recipe (and this recipe will long outlast any peat based soil) you should only expect a maximum of two to three years life before a repot is in order. Usually perennials, including trees (they're perennials too) should be repotted more frequently to insure they can grow at as close to their genetic potential within the limits of other cultural factors as possible. If a soil is desired that will retain structure for long periods, we need to look more to inorganic components. Some examples are crushed granite, fine stone, VERY coarse sand (see above - usually no smaller than BB size in containers, please), Haydite, lava rock (pumice), Turface, calcined DE, and others.

For long term (especially woody) plantings and houseplants, I use a superb soil that is extremely durable and structurally sound. The basic mix is equal parts of screened pine bark, Turface, and crushed granite.

The gritty mix:

1 part uncomposted screened pine or fir bark (1/8-1/4")
1 part screened Turface
1 part crushed Gran-I-Grit (grower size) or #2 cherrystone
1 Tbsp gypsum per gallon of soil (eliminate if your fertilizer has Ca)
CRF (if desired)

I use 1/8 -1/4 tsp Epsom salts (MgSO4) per gallon of fertilizer solution when I fertilize if the fertilizer does not contain Mg (check your fertilizer - if it is soluble, it is probable it does not contain Ca or Mg. If I am using my currently favored fertilizer (I use it on everything), Dyna-Gro's Foliage-Pro in the 9-3-6 formulation, and I don't use gypsum or Epsom salts in the fertilizer solution.

Gardening is a science.

    Bookmark   November 11, 2013 at 4:14PM
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seysonn(8a WA/HZ 1)

Gardening is a science.
I agree there is science some to it BUT I said it is not a PURE science.

Also, what I meant to say was that any "One Size Fits All" solution may not be the best approach. I just gave example:

1) Indoor/outdoor houseplants to be around for years .

2) Outdoor annual garden plants: like tomatoes, peppers. They usually last for about 6 months

so instead of 5-1-1, I may use 4- 2 -1 OR 5 - 3- 1, depending on my growing conditions. That is getting away from "one size fits all" tailoring to specific conditions to achieve better results. Then again, we are free to do and experiment and nobody is forced to do it this way or that way. I will experiment with 5-1-1 and 4- 2 -1 and 5 - 3- 1 side by side.

This post was edited by seysonn on Wed, Nov 13, 13 at 1:56

    Bookmark   November 12, 2013 at 3:18PM
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