Pro-Mix Soil: The Best Potting Soil for Organic Gardeners
Over the past 5 years I’ve tested all sorts of potting soil in my organic garden, from generic brands to in-house nursery blends and even my own DIY mixes. After trying all the options out in my home garden, the ProMix line of potting soils has come out on top as the best potting soil for me. Here’s why ProMix soil worked better for me than the other types of soilless potting mix.
ProMix Soil: High-Quality Potting Soil For Organic Gardeners
ProMix is a high-quality plant growing medium. The ProMix soil line is known for offering a variety of potting mix options, some of which are listed as safe for organic growing. My favourite potting mixes are the Organic Vegetable & Herb Potting Mix and the plain ProMix HP peat moss+perlite bales. The seed starting mix consistently performs well too.
Here are links to the manufacturer’s website with all the details for each of these potting mixes:
The Vegetable & Herb Mix is perfect for my indoor and outdoor container gardens, as it includes plant food that is safe for organic gardening. The ProMix HP adds air and bulk to my large planters and raised beds, and also works well for microgreens indoors. And the seed-starting mix is perfect for getting my homegrown tomatoes, nasturtiums, and organic pumpkins off to a good start indoors in the early spring.
Where to Find Pro-Mix Soil
Pro-Mix Vegetable and Herb Mix is available on Amazon in the US at the links in the section above. Amazon also carries ProMix HP and ProMix BX (the large bale types of promix soil). Here in Canada, I buy Pro-Mix from Home Depot, Home Hardware, or one of our many wonderful independent garden centers. Check out the Pro-Mix store locator to find a retailer near you.
The ProMix line clearly lists ingredients for all ProMix soil on product packaging and on their website. A detailed ingredient list helps prevent accidentally contaminating your organic garden with synthesized chemical fertilizer…which is actually quite a common organic gardening mistake.
What Makes Great Organic Potting Soil?
For any gardening supplies, I always look for potting soil that is safe for organic gardening, with high quality ingredients and no manufactured chemicals or contaminants. The OMRI-Listed logo is a good thing to look for when shopping. You can also look up any product on the OMRI website to see if it is listed as approved for organic use. Approved products are issued a certificate. Generic products can also be looked up (not just brand name products).
In addition to checking for organic certification, it’s important to check the ingredients. There can be a very wide range of ingredients in potting soils. Some consist almost entirely of filler ingredients (like composted lumber byproducts or manure), while others are more carefully formulated and tested to support healthy organic plant growth. The best organic potting soil has to have the best ingredients. Good ingredients lead to healthy plant growth and low potential for contamination and disease.
Most high-quality premium potting soils have similar ingredients. The best potting soil usually consists of peat moss or coconut coir for bulk volume, perlite or vermiculite for porosity (voids for air and water), and some sort of organic plant food. These mixes are often referred to as soilless potting mix as they don’t contain any soil mineral particles. Many DIY potting soils, like my own potting soil recipes or Mel’s Mix from Square-Foot Gardening, are also based on this general mix (often with homemade compost as the plant food).
The OMRI-Listed status of many ProMix products indicates the mix is approved for organic use. This is how I originally came across Pro-Mix Premium Organic Vegetable and Herb Mix. I was looking for an organic potting mix option for my container gardens and saw the OMRI organic logo.
Disclosure: Since originally testing various potting mixes, I’ve received free potting soil from Pro-Mix to test in my garden. I wouldn’t use it in my own organic garden if I didn’t trust it wholeheartedly.
ProMix Organic Potting Soil
So if most high-quality organic potting soils have similar ingredients, why is ProMix better? The biggest difference I’ve found between ProMix soil and other high-quality soilless potting mix available in my area is that the line includes an additional ingredient: mycorrhizal fungi.
Mycorrhizal fungi benefit your plants by forming a symbiotic association with plant roots. In a mycorrhizal system, the fungus colonizes the root tissue and stimulates increased water and nutrient uptake. This leads to increased plant growth. It’s a totally organic way to grow healthier, more productive plants.
- Canadian Sphagnum Peat Moss
- Peat Humus
- Organic Fertilizer
The peat in the mix provides bulk volume, holding water and nutrients to make them available to your plants. The perlite lets excess water drain while allowing the plant roots to access oxygen. The gypsum provides calcium (very important for your tomatoes!) while the limestone neutralizes the pH of the peat moss. The organic fertilizer provides nutrients for your plants and the mycorrhizae colonize the roots to stimulate increased nutrient absorption.
Using ProMix Vegetable And Herb Mix In The Garden
I’ve had excellent results with ProMix Organic Vegetable and Herb Mix. The soilless potting mix works well in the larger containers in my patio herb container garden, as soil preparation in my berry walk garden, and as the top layer of soil in my new deck raised beds. I’ve used it to grow annual vegetables, herbs, and flowers, as well as perennials like blueberries and raspberries.
The mix is light and fluffy. If you pick up the bag in the store beside a bag of generic soil, it will feel lighter due to the lack of heavy filler ingredients. The lightness of the mix allows it to retain porosity in your garden, allowing roots to access air and water (without becoming waterlogged). Due to the peat content, the mix may become hydrophobic if it’s allowed to dry out completely. If this happens, soak the soil in clean water to re-hydrate it.
Using ProMix HP For Microgreens & Wheatgrass
I also use ProMix for my wheatgrass and other microgreens. I used to just sprout the seeds in water, which does work, but I’ve found using a bit of Pro-Mix HP leads to better production more consistent growth. The greens are also more likely to survive if I forget to water it!
I did a little experiment for this ProMix review with my wheatgrass trays. I found that the trays grown with ProMix (pictured above, on the left) grew faster and produced more wheatgrass than those grown with out it (pictured on the right). I now grow my organic wheatgrass with ProMix throughout the winter. Here’s instructions on how to grow your own wheatgrass if you’d like to give it a try.
Is ProMix Worth It?
The best potting soil can be more expensive than generic options, but in my experience it’s been well worth it. I’d rather spend a bit more money up front and then have a successful garden than have to re-do work or pay to replace lower quality products. If you still don’t want to spend the money, try making your own DIY potting soil.
Outgoing links in this post may be affiliate links in which this site receives a portion of sales at no extra cost.
Here's why I love using ProMix soil in my organic garden. Your garden deserves the best potting soil! ProMix offers OMRI-listed organic potting soil and chemical-free soilless potting mix.
Best soil from Home Depot/Wal Mart
Those stores are the only place that I can buy soil and soil materials from. Can I get some recs about what soil I should use? I see all the Miracle Grow potting soil varieties, sphagnum moss, and all these different kinds of stuff with “potting soil” on its label. I notice a lot of the potting soil looks a lot like wood chip type material.
What should I buy/mix to get the best soil possible? This is primarily for outdoor. Avg. temperature 80s, high humidity as well.
Thanks for the reply. I’ve never seen coco coir in WalMart and Home Depot. Haven’t seen vermiculite either. I see perlite everywhere though.
Miracle Grow and perlite mix?
The cheapest soil you’ll be able to go with is a blend you make yourself. A basic blend is
.3 pro-mix (a premade soilless soil available alot of places.)
.3 compost (make sure its inspected by someone so there aren’t any bugs and fungus)
.15 perlite (promix already has perlite)
.15 wom castings
.10 coco coir
Won’t have a TON of nutes, but its cheap and its got enough so you don’t dump chemicals on it immediately. Make sure you add trace elements to this mix one way or another, your plant WILL need them.
the cheapest, and rather dependable soil i’ve ever used is scotts garden soil.
it’s about 3 bucks for 1.5 cubic ft at home depot and walmart.
i used it when i was learning to grow and it worked fine. it has little nute balls too, so you don’t have to feed for about 2 weeks, but they are not enough to burn seedlings. make it 2/3 soil and 1/3 perlite and you’re set. i didn’t even use perlite at the beginning and it works.
i tried miracle grow, both the regular soil, moisture control, and organic, and it’s not good. the plants get nute burned quick, and since they’re designed to be put in the actual ground, not in a planter, they are SUPER fertilized, so the nutes also seep into the ground around your plant. when using a planter, the nutes can’t seep anywhere, and burn the shit out of your plant. it can be done, but it’s a pain in the ass.
I am using a mixture of
32.5% Moo Mix Professional Potting Soil
32.5% Country Farms Organic Rich Sterilized Potting Soil
15% MG Perlite (MG was only brand i could find)
10% Sta-Green Vermiculite
10% Generic Brand Worm Castings
The mixture seems to work pretty well. All of the ingedients EXCEPT for the Moo mix, and worm casting can be bought at either Walmart or Lowes.
Does this seem like a good mixture? I’m not a pro so im not too sure just read alot of diff soil mixtures then combined them all in to one.
So is the pro mix that people refer to on Rollitup the same as sold from Rona?
Also for the compost part of soil what can you use? I have access to indoor vermecast (worm castings that have been frozen to kill off insects. Im also a newb and was under the impression that worm castings are compost?
Yes it’s the same and highly recommended by this grower, (get the HP if you can it’s got more perlite)
Worm castings is basically worm manure, not compost but pretty much the same nutrirnt level.
freezing doesn’t necessarily kill all insects BTW.
So is the pro mix that people refer to on Rollitup the same as sold from Rona?
Yes it’s the pro-mix BX. Rona has a better one from promix it’s the 100% organic mix, nice stuff.
Also for the compost part of soil what can you use?( use cow compost from Wall or home ) I have access to indoor vermecast (worm castings that have been frozen to kill off insects. Im also a newb and was under the impression that worm castings are compost? Yes it is
@frmrboi @woodsmaneh! thanks for the info! So you can use straight (no dirt? 100% promix HP) as a medium ? Then you would just feed through watering? or would you mix Pro mix with other organic nutrients.
Im very worried about gnats and other pest fuckers so should I stay away from worm castings? The stuff I was looking at is from a local farm, are there other producers that have a better chance of being bug free?
@frmrboi @woodsmaneh! thanks for the info! So you can use straight (no dirt? 100% promix HP) as a medium ? You sure can , I did for 3 years and used Botanacare pro to feed them. Then you would just feed through watering? or would you mix Pro mix with other organic nutrients. I went to 20% worm, 20% Coco, 20% ProMix and the last 20% was compost and other foods. Did it this way for another 4 years.
Im very worried about gnats and other pest fuckers so should I stay away from worm castings? No bugs in WC bugs hate WC, I buy 500 pounds of the stuff a year from a horse farm. NEVER HAD A BUG. The stuff I was looking at is from a local farm, are there other producers that have a better chance of being bug free? If it’s got bugs than it’s not pure WC.
Some light reading
[FONT="]What are Worm Castings? [/FONT] [FONT="]Worm Castings are Mother Natures soil enrichment of choice. This rich humus-like digested output of the worm includes a wide range of nutrients and microbial life that all types of vegetation require to grow. Worm Castings are one of the most natural soil enrichments available and more importantly are environmentally friendly, all natural, easy to use, and safe to handle, with a pleasant earthy aroma.[/FONT]
[FONT="]What do Worm Castings do? [/FONT] [FONT="]Worm Castings restore soil health in many ways.[/FONT]
· [FONT="]A source of organic matter with lots of nutrients a nd moisture-holding capacity. Worm[/FONT]
[FONT="]Castings hold 9 times their weight in moisture, which is beneficial in drought[/FONT]
· [FONT="]Adds active microbial life to the soil, allowing it to slowly release and make the[/FONT]
[FONT="]valuable nutrient and trace minerals more available to tender plant roots.[/FONT]
· [FONT="]Rich in growth hormones and vitamins, and acts as a powerful biocide against[/FONT]
[FONT="]diseases and nematodes.[/FONT]
· [FONT="]A natural aerator, allowing oxygen to permeate the root zone to improve drainage and[/FONT]
[FONT="]encourage root growth.[/FONT]
· [FONT="]Restores soil without fear of burning or harming tender plant life.[/FONT]
[FONT="]Restoring the soil makes nutrients more available to crops, turf applications and desired[/FONT]
[FONT="]vegetation. This means there is less need for synthetic fertilizers and pesticides. Best of all, Worm Castings contain no toxins and are therefore safe to use without fear of ground water contamination.[/FONT]
[FONT="]How are Worm Castings different from Compost?[/FONT]
[FONT="]Worm Castings are significantly better than compost. They are the result of carefully selected compost that is fully digested by worm. This makes Worm Castings an entirely mature product. It contains no pathogenic agents, and is considered a biological product which is convenient to handle. Worm Castings contain a far more diverse microbial population than other composts. These micro-organisms play an important part in soil fertility. Not only do they mineralize complex substances into plant-available nutrients, but bacteria in the worms digestive system also synthesize a whole series of biologically active substances including plant growth hormones.[/FONT]
[FONT="]How do Worm Castings work?[/FONT]
[FONT="]Worm Castings are an all-purpose natural soil enrichment that is pure earthworm castings. It is 100% non-toxic and odourless. It is the product of aerobically composted vegetable scraps fed to earthworms, and free from weed seeds, toxins and pathogens.[/FONT]
[FONT="]Worm Castings improve Soil Structure in all Soil Types[/FONT]
[FONT="]Worm Castings restore soil structure. The term soil structure is used to describe the way soil particles are grouped into aggregates. Soil structure is affected by biological activity, organic matter, and cultivation and tillage practices. Soil fertility and structure are closely related. An ideal soil structure is often described as granular or crumb-like. It provides for good movement of air and water through a variety of different pore sizes. Plant roots extend down, and soil animals including small earthworms travel through the spaces between the aggregates. An ideal soil structure is also stable and resistant to erosion. The clay-humus complex, in combination with adequate calcium which helps to bind the aggregates together, forms the basis of this structure. The glutinous by-products of soil bacteria and the hair-like threads of actinomycetes and fungi mycelium add to soil stability. All tillage operations change soil structure. Excessive cultivation, especially for seedbed preparation, can harm soil structure. Working clay soil when wet leads to compaction and subsequent soil puddling. The soil is easily puddled by rain, easily eroded, and will have poor aeration. Tillage, when too dry, shatters the aggregates. Soil structure can be enhanced by careful cultivation, growing sod crops and returning crop residues. Worm Castings (organic matter) and the humification process improve structural stability, and can rebuild degraded soil structures. Therefore it is vital to return organic material to the soil and to maintain its biological activity, which helps to improve the soil structure.[/FONT]
[FONT="]How Worm Castings work with Soil pH[/FONT]
[FONT="]Worm Castings act like a buffer for plants. Where soil pH levels are too high or low, Worm Castings make soil nutrients available again to the plant. Compared to the soil itself, Worm Castings are much higher in bacteria, organic material and available nitrogen, calcium, magnesium, phosphorus and potassium.[/FONT]
[FONT="]WORM CASTINGS [/FONT]
[FONT="]Soil organisms play an important role in forming and stabilizing soil structure. In a healthy soil ecosystem, fungal filaments and exudates from microbes and earthworms help bind soil particles together into stable aggregates that improve water infiltration and protect soil from erosion, crusting and compaction. Macrospores formed by earthworms and other burrowing creatures facilitate the movement of water into and through soil. Good soil structure enhances root development, which further improves the soil.[/FONT]
[FONT="]Restoring soil structure helps reduce runoff and improve the infiltration and filtering capacity of soil. In a healthy soil ecosystem, soil organisms reduce the impacts of pollution by buffering, detoxifying- and decomposing potential pollutants. Bacteria and other microbes are increasingly used for remediation of contaminated water and soil.[/FONT]
[FONT="]In a healthy soil ecosystem, soil biota regulates the flow and storage of nutrients in many ways. For example, they decompose plant and animal residue, fix atmospheric nitrogen, transform nitrogen and other nutrients among various organic and inorganic forms, release plant available forms of nutrients, mobilize phosphorus, and form mycorrhizal (fungus -root) associations for nutrient exchange. Even applied fertilizers may pass through soil organisms before being utilized by crops. A relatively small number of soil organisms cause plant disease. A healthy soil ecosystem has a diverse soil food web that keeps pest organisms in check through competition and predation. Some soil organisms release compounds that enhance plant growth or reduce disease susceptibility. Plants may exude specific substances that attract beneficial organisms[/FONT]
[FONT="]or repel harmful ones, especially when they are under stress from activities such as grazing.[/FONT]
[FONT="]Worm Castings stimulate microbial activity. Although earthworms derive their nutrition from microorganisms, many more microorganisms (such as bacteria, fungi and actinomycetes) are present in their feces or casts than in the organic matter that they consume. As organic matter passes through their intestines, it is fragmented and inoculated with microorganisms. Increased microbial activity facilitates the cycling of nutrients from organic matter and their conversion into forms readily taken up by plants.[/FONT]
[FONT="]Compared to synthetic fertilize r formulations, Worm Castings contain relatively low[/FONT]
[FONT="]concentrations of actual nutrients, but they perform important functions, which the synthetic formulations do not. They increase the organic content and consequently the water-holding capacity of the soil. They improve the physical structure of the soil, which allows more air to get to plant roots. Where organic sources are used for fertilizer, bacterial and fungal activity increases in the soil. Mycorrhizal fungi, which make other nutrients more available to plants, thrive in soil where the organic matter content is high.[/FONT]
[FONT="]Worm Castings contain a high percentage of humus. Humus helps soil particles form into clusters, which create channels for the passage of air and improve its capacity to hold water. The castings are in the form of tiny pellets which are coated with a gel. This crumb-like structure helps improve drainage and aeration.[/FONT]
[FONT="]Balancing Soil Nutrient[/FONT]
[FONT="]The ability of the microbiologically active Worm Castings to regenerate the nutrients from the atmosphere, organic matter and water allows them to replace those lost from chemical fertilizers by leaching, plant uptake and chemical reactions. In relation to moisture holding capacity and improvement of soil structure, chemical fertilizers have negligible effect, as they primarily consist of water-soluble salts. On the other hand, the aggregate nature of the Worm Castings has appreciable water holding capacity, and its use leads to restored soil structure and increases nutrient reserves in soil. The presence of nitrogen fixing bacteria in Worm Castings means that nitrogen can be fixed[/FONT]
[FONT="]from the atmosphere and converted to plant soluble nitrates. Worm Castings are rich in humus, which contains essential plant nutrients and micronutrients. Moreover, these castings are also rich in vitamins, beneficial microorganisms, antibiotics and enzymes.[/FONT]
[FONT="]Worm Castings restore soil, will not wash out with watering, and will not burn even delicate plants. Worm castings have a very soil-like texture and all the necessary nutrients that plants, crops and all types of vegetation require. The castings slowly release nutrients when required by the plants. Castings are high in soluble nitrogen, potash, potassium, calcium, magnesium and many other trace elements. Worm Castings allow plants to quickly and easily absorb all essential nutrients and trace elements. Because the earthworm grinds and uniformly mixes the nutrients and trace elements into simple forms (1 to 2 microns), plants need only minimal effort to absorb these nutrients.[/FONT]
[FONT="]SUGGESTED APPLICATION RATES[/FONT]
[FONT="]Potted Plants, Seeds, Seed Flats [/FONT] · [FONT="]Use 1 part Worm Castings to 3 parts potting soil mix[/FONT]
[FONT="]Potted Plans, Window Boxes, Hanging Baskets ([/FONT] [FONT="]established)[/FONT]
· [FONT="]Add 1 to 2 inches of Worm Castings to top of soil[/FONT]
· [FONT="]Mix in, taking care not to damage shallow roots[/FONT]
· [FONT="]Water well[/FONT]
· [FONT="]Repeat every 2 to 3 months[/FONT]
· [FONT="]Use Worm Castings as a top dress at 10 lbs. per 1000 sq. ft.[/FONT]
· [FONT="]Apply twice a year in spring and once again in late fall[/FONT]
· [FONT="]Apply 10 lbs. of Worm Castings to 1000 sq. ft.[/FONT]
· [FONT="]Work lightly into topsoil[/FONT]
· [FONT="]Mix in grass seed[/FONT]
· [FONT="]Cover with shredded straw and keep watered[/FONT]
[FONT="]Roses, Trees, Bushes, Berries[/FONT]
[FONT="](new or freshly transplanted)[/FONT]
· [FONT="]Mix 1 part Worm Castings to 3 parts soil[/FONT]
· [FONT="]Surround newly dug hole with mixture[/FONT]
· [FONT="]In the hole, spread root over a mound of the mix, and cover[/FONT]
[FONT="]Bushes [/FONT] · [FONT="]Use 5 lbs. of Worm Castings per 10 Bushes[/FONT]
[FONT="]Perennials [/FONT] · [FONT="]Work ½ cup of Worm Castings into the soil above root zone,[/FONT]
[FONT="]taking care not to damage the shallow roots[/FONT]
· [FONT="]Apply in spring, early summer, and fall[/FONT]
[FONT="]Tables and Annual Flowers [/FONT] · [FONT="]Line bottom and sides of plant holes/seed furrows with[/FONT]
[FONT="]1 to 2 inches of Worm Castings[/FONT]
· [FONT="]Set plants/seeds in place and cover with soil[/FONT]
[FONT="]During the growing season, side dress once every 2 months at a[/FONT]
[FONT="]rate of ½ cup per plant or 1 cup per linear foot of row[/FONT]
[FONT="]Gardens [/FONT] · [FONT="]Apply 5 lbs. of Worm Castings per square foot[/FONT]
[FONT="]Note: [/FONT] [FONT="]The release time for nutrients is around 4 months for continual release of nutrients.[/FONT]
[FONT="]Repeat application is recommended at 4 month intervals.[/FONT]
[FONT="]Application rates may vary depending on soil test results.[/FONT]
What's up guys. Those stores are the only place that I can buy soil and soil materials from. Can I get some recs about what soil I should use? I see…