There are so many recipes. Maybe not as many as bread recipes, but sometimes it seems that way. As when I bake bread, I'm a little of this, little of that, kind of guy.

Probably the thriftiest way to reuse potting soil is to screen it, or at least pull out big bunches of roots, and then mix in an inexpensive, but not too inexpensive potting soil.

Beyond that ... well if you want to make it a mini project, google "potting soil recipes" and compare the ingredients you find to what is cheap and available locally. Rice hulls may be dead cheap in central California, but not so much in Canada, on the other hand Canadian peat should be available at a good price!

I suggest you play with it, and try a few things, in a few test pots.

Update: I personally would be brave enough to mix old potting soil with Premier Potting Soil, 25 L for $3.99 from Canadian Tire and see how it goes.

This post was edited by johns.coastal.patio on Thu, May 15, 14 at 20:33

There is a recipe many of us who hang out on this forum use for annuals and vegetables: it's called 5-1-1 and is described in the link I'll give below. It is cheaper than using store bought mix and works a lot better. It does not require any sifting (although some purists do sift ingredients, I never do). The catch is that it requires finding a source of pine bark "fines" which are pieces of bark that are smaller than 1/2 inch in diameter. This ingredient is called different things in different places, including pine bark mulch and soil conditioner.

I wouldn't reuse used soil from your neighbor unless it is very loose and "fluffy", in which case you might use it in place of the peat in the 5-1-1 recipe. It's a long post, but if you are willing to take the time, you will learn a lot. Even if you choose not to make 5-1-1 it will help you judge how well other mixes are likely to work.

Here is a link that might be useful: Container Soils -- Water Movement and Retention

So, what is the typical cost of 5-1-1 per cubic foot?

I'd guess that it might break down by region, and if the "5" part was cheap in your area, it will be cheap overall. northerner_on may indeed have a cheap source for pine bark fines, and that could be a deciding factor.

On the other hand, surely many folk are many miles from actively harvested pine forests, and that makes a difference.

The 5 part is the pine bark which I can get for less than $2 a cubic foot, not an unusually low price across the US. My last batch of 5-1-1 cost about $3 a cubic foot. The perlite is the most expensive component. By comparison, MiracleGro potting mix is at least $4-5 a cubic foot while Promix can be more than $12 per cubic foot.

I cannot find $2 per cu ft for pine bark fines in California. Maybe $3, which would just about match the price of pre-finished Kellogg outdoor potting soil, which is my application.

"Kellogg 1.5 cu. ft. Patio Plus Organic Plus Outdoor Potting Mix" currently $5 (ORMI listed, even)

Update: Oh, if you can make this rebate work, it is only $4 per 1.5 cu ft.

This post was edited by johns.coastal.patio on Thu, May 15, 14 at 22:40

Thanks everyone.

John, your idea sounded right up my alley. I have emptied the potting soil from my neighbour's pots and it's very light and may be primarily peat moss because it won't 'wet' easily. So mixing that with some Canadian Tire potting soil and adding some compost or manure seems appropriate.

Ohiofem, I do not think that pine bark fines are readily ( read cheaply) available, but I wonder what the purpose of that ingredient is. Perhaps a carbon source. I have large amounts of rotted logs around, all crumbly, which I have stored in plastic bags to germinate and kill off the weeds. Could that be used instead? Does it have any use in a container mix?

Having read the recipe, I think much of the conversation centred around perennials and trees in pots which is not the case for me. I will just grow these plants over the summer, and in addition since it is not my garden soil, I will fertilize them quite heavily.

I will consider the 5-1-1 for an indoor plant which I plan to re-pot this spring. It is a double red hibiscus, which has been in its present pot for a few years, but it is horribly pot bound so I will have to do a complete re-pot, pruning roots etc. It is in a large ceramic pot and I don't want it any larger. I think 5-1-1 will provide it with more nutrients and blooms which are very few these past two years.

So thanks again, I got lots of work to do. Happy Gardening!!!

There are two different mixes described in the link I posted. Much of the discussion was around the "gritty mix," which is recommended for trees and perennials. The mix I was talking about is the 5-1-1, which is intended for annuals, including flowers and vegetables grown for only one season. Hundreds of people who have come to this forum have used it over the past 10 years and most found it significantly better than mixes made up primarily of peat.

Both mixes call for conifer bark. Rotted wood or any kind of sap wood will not work well as a container medium. It will rob your mix of nitrogen. The purpose of pine bark is to help your medium retain its structural integrity and to create a favorable environment for plant growth. It is not intended as a source of carbon or any nutrients on its own.

And, FWIW, another forum member in Ontario used Alltreat Canada Redî Pine Bark Mulch and said it seemed perfect for the 5-1-1 mix.

Thanks for the explanation and the information on the Red Pine Bark Mulch. That is readily available here at Home Depot. The 5-1-1 is turning out to be more within my grasp than I thought. Lots more to do. Thank you so much.

Hi I just ordered the Alltreat Canada Redî Pine Bark from Home Hardware in Montreal. It's $6.49 for a 2 cu.ft. bag. Last year I used hemlock mulch in the 5-1-1 mix, and it worked well, but the Alltreat looks like a better option.

"Hundreds of people who have come to this forum have used it over the past 10 years and most found it significantly better than mixes made up primarily of peat."

I'd look for actual controlled experiments along those lines ... as for instance in this PDF:

Potting soil label information is inadequate

Interesting to note that the two "excellent" mixes at growing tomato seedlings there were pretty much bark, peat, and sand ... with sand being so much out of favor now.

JCP: I've noticed that many of your links are to sources that are quite old. That one discusses potting soils available in California in 1984. I doubt many of those formulas are the same now if they are even available. The OP asked about a recipe for making your own mix. If you want to see discussions of controlled experiments on substrate components, go to scholar.google.com and search on some components used in containers. Many things have changed since 1984, especially what's available to the home grower. Here's just one more recent controlled experiment comparing perlite and pine bark. There are many more, but you get the idea.

Here is a link that might be useful: Successful Beit Alpha Cucumber Production in the Greenhouse Using Pine Bark as an Alternative Soilless Media

Is "old" really a solid criticism? Aren't soil, compost, and plants all quite "old?"

What exactly are you suggesting, that plants have changed, or that the would has changed so much that "excellent" isn't "excellent" anymore?

Also, in argument it is "an appeal to missing data" to say "go find other studies, which will prove my point."

Until YOU provide the newer studies, YOU have not made your case.

I should probably remind you all at this point that I am not a One True Anything kind of guy.

I understand that there are many, many happy users of 5-1-1, just as there are many, many, happy users of MiracleGro, or Hydroponics, or Permaculture methods.

My suspicion is actually that as we get to be better gardeners out ability to use all these things increases.

They all work, though there are certainly ways to fail with each one as well.

We can note though, that in an adjacent thread, people are marveling at PharmaChad's success with his Bucket Garden.

His mix does actually sound like the two "excellent" types out of 1984.

Maybe things don't change that quick.

Yes, better gardeners are able to work around the inherent limitations (limiting factors) of specific ingredients, mixes, and conditions.

John, you have to remember that the 5-1-1 is a *starting point.* You'll see many of us recommend following the original recipe to gain an understanding of how a bark-based mix works, but after that we're fairly vocal about tailoring the 5-1-1 to the individual's growing conditions. In Florida, less moisture retention; in Las Vegas, more moisture retention, and so on.

For example, I've always used uncomposted fir bark for the 5-1-1; I've never used straight peat moss; and I have used Turface as a substitute for the peat portion.

Josh

Josh, I am absolutely fine with 5-1-1 straight up, or varied.

It's just "5-1-1 for world domination" that sometimes gets me down.

I personally believe that choosing your mix, once you learn the ropes, should be a personal and local decision. It should be shaped on your climate and your prices.

I'm down on "Mel's Mix for world domination" for the same reasons. If you have pretty good soil, you may just need the standard application of compost, and a standard (per box) application of a time release fertilizer to be good to go.

My take on 5-1-1

COST: as Ohiofem's ~~$3 per cu-ft (average). But it took me some time to figure out to get WHAT from WHERE. Conifer bark (mostly pine) is bagged and marketed as MULCH. They come in all shapes and sizes from CRUSHED, mini/small nuggets, medium and large nuggets. But because they are sold as landscaping mulch, often have a lot of sapwood ( a no no for 5-1-1).
So the difficulties about 5-1-1 Are:
---- Finding the right stuff.
--- even after finding the RELATIVELY right stuff you may have to need to screen.
--- Then you have to make the mix, per recipe'. ( add perlite, peat moss, lime, crf )

I think, for someone who can do all the work, 5-1-1 is a better potting mix, REGARDLESS of being economical or not. I have done a lot of studying on this subject, b,c I was going to do a lot of container growing this season. Right now I have about 22 potted peppers and tomato, all filled with 5-1-1( Slightly modified formula) . I have even used it in the tomato planting holes. I estimate that I have made about 14 cu-ft of it. The most expensive part is perlite ($17.00 for 2 cu-ft). The rest of ingredients cost around $2.25 per cu-ft

So as Josh said, You have to have some experience and feel for potting soil and adjust to your climate. For me, in PNW the 5-1-1 mix is almost perfect. We have cool weather and more rain. So drainage is important. If I was going to use it say in Central Texas I would modified it with MORE peat moss and/or Floor Dri (OptiSorb).

I can say in summary that perhaps 5-1-1 is not for everyone.

Well, let me ask you this:

Surely commercial greenhouse tomato growers are the most performance and cost driven users in any room.

Do they use 5-1-1 predominately?

I think the interesting thing, when we get away from houseplants and such, and to pretty much "production" use, there is a great deal of serious study.

Update: Reviewing papers from University of Florida, Vermont, and Cornell, I see a variety of choices, from pure rock wool, to pure bark fines, to peat based mixes.

As I say above, perhaps they all work.

This post was edited by johns.coastal.patio on Sat, May 17, 14 at 17:31

There are many nurseries that use bark in their mixes, along with the other ingredients that make great container mixes - perlite, pumice, scoria, and various grit.

They can all be made to work, yes; just as they all have their limitations (including bark mixes, of course). My focus is hot peppers in containers during the Summer, although I also grow a Sun Gold tomato in 15-gallons of 5-1-1. I have more success in the long-term with durable bark mixes than in peat-based mixes, and the cost is much less (than the Ocean Forest by itself, which I use in place of the straight peat in the 5-1-1).

Greenhouse tomato growers - starter plants, I assume? - grow quickly and don't require a durable mix for the grower to quickly move to market....and after that, it's up to you to replace the mix or pot up.

Josh

Actually, I'm talking about the greenhouse production folk, who are pretty much the only commercial growers who produce fruit from container grown plants.

The Greenhouse Tomato Handbook, from Mississippi State University Extension Service says (in 2010) that many growers there use straight bark fines, irrigate with 2-3 quarts per adult plant per day:

"In pine bark, 6 to 12 waterings per day are usually adequate."

That's interesting, right?

If you are doing it the drip way, you want to spread them out, and issues with flood watering become less applicable.

Update: not that this is the only way. Up north, UMass Extension claims:

"Most commercial greenhouse media for container crop production contains 30 to 60 percent peat moss alone or in combination with composted pine bark. Other materials such as vermiculite and perlite are added to affect water retention and aeration."

If you look to "organic" mixes, such as those recommended by North Carolina State University, things become even more varied.

This post was edited by johns.coastal.patio on Sun, May 18, 14 at 10:11

Here is that North Carolina paper, updated 2010:

Potting Mixes for Certified Organic Production

Appendix 3 - Recipes for Growing Media, shows amazing variation.