Here’s my problem…I really like Pro Mix. Pro Mix is very hard to find in my location and ordering it seems to at least double its price. I am thinking about mixing my own potting mix and want your input. I have researched the threads here and many are from 2015 or later and have read some of the Houzz threads where you guys have contributed from even earlier than that. Has anyone settled on a best recipe? Anyone out there making a mix similar to Pro Mix?
Katy
I have no idea what Pro Mix is made of. I do my own mix which is 4/5 compost and 1/5 DE and am quite happy with it.
I am fortunate that medical mary Jane is legal here because promix is on every corner practically. Less than 25.00 a bale. Promix is a great product. With that being said I want to start making my own mix too.
I found three 2cu bales of it in a walmart closeout for $5 each last year. I cannot find it locally now…
$39.00 a bale with $37 for shipping…I can’t handle that but I really love the product!
The bales of the HP version are just Canadian sphagnum peat moss with some dolomite lime to offset the acidity, and then has some perlite in it, plus they add some mykos… There may or may not be other ingredients but that’s the basic mix. They also have numerous other variations however so when you say Pro-Mix you need to be more specific if you mean the bales or pre mixed potting mixes…they have a website. I have taken to making my own from scratch and adding amendments as needed for different plants.
I am just exploring this topic myself. Yesterday I went to a landscape supply company and scooped up a 5 gl. bucket of conifer bark with a mix of fines and coarser ground pieces = $2. I potted up about 20 fig starts about 12 days ago and was concerned that the mix I used ( = peat, perlite, a little lime, etc.; some store-bought with a lot of cheap [my own peat and perlite] added to stretch the $) was holding too much water and would rot the roots. Things have turned out OK, but I’m going to add the bark into this next batch. People use all sorts of mixes…often 5-1-1-1-1 (web search) or a variation of it. One person summed it up well though by writing that, many variations of mix will work.
They need some food in a container at some point…don’t over-water them. Basic stuff.
Edit: I forgot to mention dirt…I used a little regular dirt which in my yard is a bit red clay though kind of loamy, with a bit of organic in it.
The more I read the more I wonder just how much it does matter. However I have used cheap bag mixes with vegetable seedlings and wondered why they wouldn’t grow and after I added fertilizer (that was supposed to be included in the mix) they did start growing. when using the ProMix they grew like crazy…so, was it the fertilizer or more of a balanced mix or less water retention or ???. I just know that I have been very satisfied with my plants in this medium but I’m running out and I cannot afford to purchase it. That being said I have a list of the ingredients and I’m going attempt to find the right mix for it. I can find all the ingredients but don’t know all the ratios. I have found a good article from Penn State that helps a bunch.
https://extension.psu.edu/homemade-potting-media
Katy
I worked out several homemade mixes that work pretty well. The key with all of them is to sterilize before use.
1 - 5.3 cubic foot bale of peat moss
3 gallons perlite
3 gallons vermiculite
15 gallons high quality compost or worm castings
1 quart dolomite lime
A 5.3 cubic foot bale of peat moss when expanded is about 25 gallons. This mix will be slightly acidic, down around 5.0 so if growing veggie seedlings, it will need 1 quart of finely ground dolomite lime thoroughly mixed in… This mix will have plenty of nutrients to support growth for up to 6 weeks.
So what about sterilizing?
1 - turkey fryer
1 - 55 gallon steel drum
4 - bricks
tools to cut the top out of the drum
I cut the top out of the 55 gallon steel drum, place 4 bricks in the bottom of the drum, place the cut out top of the drum on the bricks, put water in to cover the bricks, then fill the drum with potting mix. Place a piece of sheet metal on top of the drum to hold in the steam. Turn on the turkey fryer with the drum on top and let the water in the drum boil for 1 hour. Do not boil too hard or all the water will evaporate. You want it hot enough to have steam running out the top of the drum after filtering through the mix to sterilize it… Turn off the turkey fryer and let the drum cool overnight.
How do you mix this up in large volume? I put a sheet of greenhouse plastic about 20’ X 20’ down on the ground and put all the ingredients on top. Bust up the peat moss by hand. Then use the plastic to roll the mix around several times until it is thoroughly mixed. With practice, this only takes a few minutes. The sheet of plastic can then be used to transport the mix or can be used to dump it into a barrel for storage. I suggest getting help with this part since the mix can be fairly heavy depending on moisture in the compost.
Every year I pot up about 75 5-gal pots with apple trees, and have tried all kinds of bagged and bulk nursery potting mixes. After 8 years nothing has given the same growth as plain dirt from the yard, amended a little bit with ammonium sulphate and soil sulphur due to our high PH. I mulch the pots with shredded apple prunings from the last season, which adds organic matter every year to the dirt. I keep using the same dirt year after year in the same pots without sterilizing it. The years with the commercial and bagged potting mixes have been disasters, never again.
I buy pine bark, the smallest I can find, or use soil conditioner which is pine bark in these parts. Good pine bark is hard to find. Pro-mix general purpose mix is not as expensive.
I use
3 parts pin bark fines
1 part compost
1 part Pro-mix GP
1/2 part DE (size of perlite Napa floor dry, or any 100% DE floor dry product. Can substitute with perlite. A little of both is great!
I have used it for three years, and I’m happy with it. You could use peat moss instead of pro-mix. Soil will be slightly acidic. The compost will keep it down. using tap water to water will add carbonates and slowly knock it down too.
I decided to make my own mix last winter. I used to use pro mix but I find that the peat based mixes dry to quickly in my greenhouse and I end up fighting with the plants all summer long. I wanted something with better nutrients and water holding capacity.
We farm so I have a ton (or tons) of well composted manure I mixed it 50/50 with Pro Mix in my compost tumbler. I tumbled it for about 3 months. It seems to be doing the job, I started all my cut flowers, tomatoes, and melons about a month ago and there are no issues yet. We will see what the long term results are.The tumbler is in a heated place so when one batch is done, I put it in a large container and start another.
I got the idea from a “pot” grower at a hydroponics store who uses composted manure and reconstituted coir brix. He says the 3 months of mixing is critical for a good final product. I must admit, the soil at the end of the process looks far better than the initial mix. I couldn’t find coir last fall so I used a bag of Pro Mix but his soil was phenomenal so I am going to stock up on coir brix this fall and make it his way this summer.
I admire you mixed it for 1/4 of a year. Wish i had that kind of time! 
Your arms must be sore!
Here is my mix, though it’s a rough ‘recipe’ as I don’t measure and it’s shovel-fulls into a wheelbarrow. I’ve been using more or less the same thing for decades and it works well for me. Mostly for vegetables in the greenhouse (winter eating and spring starts) and a few cuttings.
I put a 1/2 inch screen sifter on a wheelbarrow and shovel in and sift as I go:
a half dozen shovels of compost (a wooden paddle helps push damp compost through the screen)
maybe half that amount of garden soil (we have sandy-loam soil and I usually take it from the paths between beds). I haven’t always included garden soil but feel the mix was too rich without it, making my winter lettuce grow too whimpy.
several or more shovels of sharp sand (sifted gravel type sand not the soft sand of most soils). I’ve used Lake Superior beach sand, too (it’s a sharper sand than the fine Lake Michigan sand) but like the sifted gravel better.
a generous dusting of wood ashes
a shovel or so of old sawdust or shredded dry leaves or well dried grass clippings to help lighten the mix.
Mix it all up with shovel or hoe (one with rounded edges works nice in the wheelbarrow, like you’d use for mixing cement). In the fall I fill my winter flats and a galvanized garbage can so I have it ready for use mid winter and spring. This year I happened to have some vermiculite so have added that to my seed starting pots/flats and cuttings. Can’t really tell if there is a difference.
I don’t sterilize my soil so I get some weeds; easy to pull out. I have a permanent bed on the north side of my greenhouse (bench for pots and flats on the south). This soil never gets ‘changed’ but I dig plants in from the garden to the bed in the fall and often dump used flat soil there. Any extra goes back out to the garden.
In the spring I have run out of mixed potting soil and simply gone out to garden and dug up soil from a bed and used that. It worked, too. Reading all the different mixes folks use successfully it’s obvious there’s no one ‘right’! But the conditions one is growing in probably makes a difference, too. Sue
Here’s a photo of the larger sifter I use. It’s really handy. We found it and a companion at a garage sale for a few dollars many years ago. One had 1/4" hardware cloth bottom, the other 1/2". What a find! They were old and used and very well made. They have continued doing great service all these many years. Here I’m cleaning/sorting dry beans (I just swiped the image from our website but I might have some better photos if anyone’s interested for making one).
I used my compost tumbler LOL, and it was winter so there was not much else to do.
I’ve had good success with miracle to garden soil and add some perlite. I usually try and get as much of the bigger sap wood pieces out.
I need one of those, I have no room anywhere to do it on the ground. Plus the bonus of mixing my soils! I use garbage cans and a pitch fork now. You know studies of compost and root rot show that compost contains bacteria that like to eat the root rot fungus. Compost prevents root rot. Google root rot and compost on Google scholar and numerous studies pop up that confirm it. Interesting in one, even the crappy compost helped some, every compost tested worked to some degree compared to the control. In the UK they use compost in all potting mixes, bagged or otherwise.
Sifted compost. Maybe 70 percent or so. Peat moss for the rest. Diatomaceous earth.
I get Optisorb sweeping compound from the auto parts store for the diatomaceous earth. I don’t know— add some. ( Be sure and wear a mask while handling.) Until it looks like the dispersion of vermiculite in a bag of retail potting soil, maybe.
I put the bigger sticks at the bottom of the container, the unsifted compost and peat mixture in the middle and the sifted stuff with the Diatomaceous earth on the top few inches.
I’m not saying it’s the greatest. I’m saying it works.
A lot of people say that compost is a bad thing in potting soil because it’s too water absorbent. Well, it’s no more water absorbent than peat moss and we use that all day long for potting soil. I do live in an arid climate and use porous grow bags, however.
I’d say that the main disadvantage in my mix, is that you really have no idea what nutrients are in your compost. Also, it presents a moving target since the breakdown of the stuff presents a certain amount of continued competition for N. It can be compensated for, but how much?
The main advantage is that it is cheap, easy and lasts longer than regular bagged potting soil
I love my tumbler, it was bought to make compost but I never used it much because my chickens got all my scraps, so I started using it to mix soil. I sell fresh cut flowers all summer so I have to start lots of seedlings in the spring. I think I just got tired of wrestling with the different mixes as well as having to pay more each year for a bale.
I have well rotted manure up the ying yang, and yet I never really considered it as a good compost source, why I do not know. I have been buying potting soil by the bales for years, assuming it was a magic mix that could not be duplicated.
I agree with you, That is correct, I myself happen to like peat. I find it predicable, and consistent. I know the disadvantages and prevent them. It’s not the mix, it’s the gardener. A good gardener could grow tomatoes in broken glass.
You know I use only one part com[post because I want it for root rot prevention, not really to feed my plants .It’s not just root rot, when an ecosystem is filled, pathogens cannot find a niche and move on. It’s not just root rot. This same principal was taught to me about the human body and disease, in my formal studies at MSU. It’s the same thing with plants. It is more sophisticated than one would think too. Feed the soil, the soil will feed the plants.
Most plants like an NPK ratio of 3-1-2. Exceptions certainly exist, this is the ,mean number. I feed the soil in containers by using organic fertilizer, any kind. And in the spring I use Dynamite control release fertilizer. It lasts 9 months (which really means it’s lasts 4.5 months). Always cut the number in half if your temps go over 80F it is released twice as fast. That is good enough for once a growing season. It has all micros and has a ratio very close to 3-1-2 (15-5-9). Once a month I hit them with an organic. This has been working great for me. You can get 7 pounds of Dynamite for 22 bucks free shipping at the Seed Ranch. If you need more than that feed stores sell bulk slow release. Not as good, but should work fine. Also bulk grains can be used for organic fertilizers, like cotton seed meal, Alfalfa is very good! Holly-tone is most places is 20 pounds for 20 bucks, good deal, great stuff! Look for sales at the end of the year.
I have little time, I can’t be putting fertilizers in the water every time I water. And my method is not a compromise, I would put my fertilizer regiment up against any others.
I use other fertilizers for plants that don’t fit the norm, like blueberries or cacti.
I grow both and have a different fertilizer regiment.
They also include something to improve water absorption. When peat moss dries it repels water.
I make a mix for fruit trees that is 1/3 compost, 1/3 peat moss and 1/3 either perlite of sand- by volume. Perlite when I’m trying to reduce weight. For this purpose it is better than pro-mix and the compost adequately sweetens the peat. When well mixed, the water repellency of peat moss is neutralized and the recipe is better for fruit trees than pro-mix for me, which is lighter and holds less water. I don’t have drip installed in my nursery and water by hand with a hose (I’m an idiot, by the way).
Pro mix sells for about $40 a 3 cubic yard compressed bail around here but a local green house operator sells me bails of a similar product for $25. If you have any such businesses near you you can ask them to sell you some. I only use it for starting vegetables- I give a lot of free tomato plants away in up to 2 gallon containers. I also grow certain things in containers to reduce root insect pressure- mostly parsley, which we use in large quantities.