Potting Soil vs Potting Mix: What 11 Bag Labels Actually Contain

Most answers to potting soil vs potting mix say potting soil contains real dirt and potting mix does not. The trade’s own paperwork disagrees. The Mulch & Soil Council Uniform Product Guidelines (revised September 2026) define a single category, "Potting Soil/Mix," in standard, premium and professional grades, with no soil-content test for either word. On the council’s certified product list (file dated April 11, 2024), 6 products named "Potting Soil" and 26 named "Potting Mix" carry the same "Certified Premium Potting Soils" mark.

So the useful question is what is in the bag. Below are the ingredient panels of 11 container products from 8 makers, the two that list a mineral soil ingredient, and the drainage physics that make a soilless blend the safer choice in a pot. For garden beds and grading, the labels on bagged topsoil and garden soil are compared in our topsoil vs garden soil label comparison.

What do the industry definitions say?

The Mulch & Soil Council (MSC) writes the voluntary label rules that certified brands must adopt. Its guidelines define horticultural growing media as anything sold to grow plants in containers, then grade it. The word "soil" carries almost no meaning by itself: the MSC repeats a NIST definition in which "soil" is any product, except peat or peat moss, sold for use as a growing medium, soil amendment or soil replacement.

Term on the bag	What the definition requires	Source
Potting Soil/Mix, Standard	Supports plants in containers and exchanges air, water and nutrients	MSC UPG, Part II 2(b)
Potting Soil/Mix, Premium	Standard, plus actively promotes growth or vigor of container plants	MSC UPG, Part II 2(a)
Potting Soil/Mix, Professional	Premium medium with documented sales to commercial growers	MSC UPG glossary
Soilless	Without naturally occurring earth soil such as topsoil, mineral soil, clay and silt	MSC UPG glossary
Soil	Any product except peat or peat moss sold as a growing medium, amendment or soil replacement	MSC UPG, citing NIST
Potting soil (older MSC glossary)	Made primarily from natural materials such as bark, peat, humus, compost or manure; sand allowed as an additive	MSC glossary
Planting mix (older MSC glossary)	Made primarily from natural soils, peat, humus, compost or manure	MSC glossary
Specialty soil	Material designed primarily as a seed starter	MSC UPG, Part II 2(c)

Two things follow. First, a bag called potting soil is not required to hold mineral soil; the MSC glossary built the term around bark, peat, humus, compost and manure. Second, the one consumer term in that glossary that names "natural soils" as a main ingredient is "planting mix," not potting soil. The glossary also sets the same pH window for potting soil and professional mix: 4.5 to 7.5, with soluble salts of 0 to 5.5 millimhos/cm.

What is in 11 bags sold as potting soil or potting mix?

We read each maker’s own ingredient statement: label scans posted with retailer listings, maker product pages, FoxFarm’s label text pages and one E.B. Stone safety data sheet. Miracle-Gro’s label wording changes by state; the Miracle-Gro Potting Mix label prints separate ingredient lists for California, Texas and Idaho, New Hampshire and Georgia, where forest products are 45 to 55 percent.

Product (maker source)	Name says	Organic base	Aggregate	Wetting agent or yucca	Sand, silt, clay or loam listed?	Analysis (N-P-K)
Miracle-Gro Potting Mix	Mix	One or more of processed forest products, peat, coir, compost; sphagnum peat moss	Perlite	Wetting agent	No	0.21-0.11-0.16
Miracle-Gro Performance Organics All Purpose Container Mix	Mix	Sphagnum peat moss, processed forest products, compost	Perlite	Yucca (not called a wetting agent)	No	0.19-0.03-0.03
FoxFarm Ocean Forest Potting Soil	Soil	50 to 60% aged forest products, sphagnum peat moss (group also lists perlite, sandy loam, fertilizer)	Perlite	None listed	Yes: sandy loam	0.30-0.45-0.05
FoxFarm Happy Frog Potting Soil	Soil	50 to 60% aged forest products, sphagnum peat moss (group also lists perlite, fertilizer)	Perlite	None listed	No	0.30-0.30-0.05
Espoma Organic Potting Mix	Mix	60 to 70% processed forest products, sphagnum peat moss, humus	Perlite	Yucca extract (not called a wetting agent)	No	Not printed on maker page
PRO-MIX Premium Potting Mix (US)	Mix	Canadian sphagnum peat moss, peat humus	Perlite; polymer gel (US only)	None listed	No	Not printed on maker page
PRO-MIX Premium All Purpose Mix	Mix	Canadian sphagnum peat moss, peat humus	Perlite	None listed	No	None listed
Black Gold Natural & Organic Potting Mix	Mix	Bark, Canadian sphagnum peat moss, compost	Perlite; pumice or cinders	Organic wetting agent	No	0.09-0.03-0.03 (MSC certified list)
Kellogg Patio Plus Premium Outdoor Potting Mix	Mix (MSC list: Potting Soil)	Aged recycled forest products, aged rice hulls, composted poultry manure, peat moss	Perlite; rice hulls	None listed	No	0.30-0.10-0.10
Great Gardens Professional Potting Mix	Mix	Sphagnum peat moss, processed forest products, compost	Perlite	Yucca (wetting agent)	No	0.17-0.10-0.12
E.B. Stone Edna’s Best Potting Soil	Soil	Fir bark, peat moss, redwood compost, mushroom compost	Volcanic pumice	Yucca saponin (not called a wetting agent)	Yes: sand	Not in SDS

Only 2 of the 11 list a soil mineral. FoxFarm Ocean Forest Potting Soil names sandy loam inside its 50 to 60 percent group of forest products, peat moss, perlite and fertilizer, and the E.B. Stone Edna's Best Potting Soil safety data sheet lists sand among 15 ingredients. Both are sold for containers. The third "soil" bag, FoxFarm Happy Frog Potting Soil, lists no mineral soil at all.

The names also cross over at the maker level. Kellogg sells Patio Plus as a "Premium Outdoor Potting Mix", while the MSC certified list carries it as "Patio Plus, All Natural Outdoor Potting Soil." Espoma calls its Organic Potting Mix "the ultimate potting soil" in its own product copy. A Washington State University Extension master gardener article sums up the shelf: the vast majority of bagged "potting soil" is ground wood and bark from recycled forestry products. The same article adds that bags heavy in those forest products have no clay to hold potassium, calcium and magnesium, so those nutrients leach unless well-composted material is mixed in.

What actually varies is the feeding. Six bags print a guaranteed analysis between 0.17 and 0.30 percent nitrogen. Miracle-Gro says its potting mix feeds for up to 6 months; Premier Tech claims up to 9 months for the PRO-MIX Premium Potting Mix with controlled-release fertilizer. Espoma tells buyers to feed at least monthly starting 2 weeks after planting. If you grow organically, the Miracle-Gro Potting Mix label lists polymer-coated ammonium nitrate and ammonium phosphate; the FoxFarm, Espoma, Kellogg and Black Gold panels list organic sources such as castings, guano, feather meal, kelp meal or "organic fertilizer" instead. How these numbers compare with lawn products is covered in our guide to reading the three numbers on a fertilizer bag.

None of the 11 panels lists vermiculite, the aggregate many guides name first. Perlite appears on 10; the MSC defines horticultural perlite as volcanic glass heated to about 1,600°F so it expands 13 times its volume. Black Gold adds pumice or cinders, Kellogg adds rice hulls, and E.B. Stone uses volcanic pumice alone. The compost several bags contain is the same material compared in compost vs mulch lab numbers, so a heavy compost share means more fines and more water held.

Why do containers need a soilless mix?

The reason is the perched water table. After you water a pot and it stops dripping, a layer at the bottom stays saturated no matter what the mix is. NC State researchers showed it with a sponge of 80 percent total porosity in the N.C. Flower Growers' Bulletin (August 1995): the same sponge held 4.2 percent air when stood 2 inches tall, 14.8 percent at 4.25 inches and 46.5 percent at 8.5 inches.

1. 2 in tall4.20%
2. 4.25 in tall14.80%
3. 8.5 in tall46.50%

Source: NC State University, Fonteno, Bailey and Nelson, N.C. Flower Growers' Bulletin, August 1995 One sponge with 80 percent total porosity, stood at three heights. The shorter the column, the larger the share left saturated: the perched water table effect.

Show the numbers

	Air space after drainage, % of volume
2 in tall	4.20%
4.25 in tall	14.80%
8.5 in tall	46.50%

Measure	Value	Source
Sponge air space at 2 / 4.25 / 8.5 in tall (80% total porosity)	4.2% / 14.8% / 46.5%	NC State, Fonteno, Bailey and Nelson, 1995
Air space in short vs tall plug cells, same 4 mixes	1% to 3% vs 5% to 10%	NC State, 1995
Effect of packing the mix into the pot	Air space cut in half or eliminated	NC State, 1995
Air pore space below which root dieback and disease may follow	15% to 20%	Ontario aeration porosity factsheet (OMAFRA-supported)
Desirable air pore space, container nursery production	20% to 30%	Ontario factsheet

A shallow pot behaves like the 2 inch sponge: most of its depth sits in the wet zone. Mineral soil makes that zone wetter: the WSU article puts silt particles at 0.002 to 0.05 mm and clay under 0.002 mm, and the fine pores between them hold water rather than air. That is why peat, bark and perlite blends dominate bags for pots, and why the NC State authors warn that packing a mix can eliminate air space. By the same height rule, a gravel layer in the bottom only shortens the column of mix above it, so the wet layer moves up rather than away. If your plant wants acidic conditions, check the panel for limestone, which Espoma, both PRO-MIX bags and FoxFarm Happy Frog (as dolomite lime) list, before you adjust pH with our sulfur rates for acid-loving plants.

How can you test the bag you bought?

You can measure air space at home with the method in the Ontario aeration porosity factsheet, using a pot of at least 1 liter (about 1 quart) with one drain hole:

1. Pre-moisten the mix 12 to 24 hours ahead until a squeeze barely drips, then seal it in a bag overnight.
2. Plug the drain hole, fill the empty pot to the brim with water and record that volume in mL (line A).
3. Empty the pot, fill it with the moist mix packed as firmly as you would when potting, and scrape it level with the rim.
4. Add water slowly, over up to an hour, until a thin film glistens on top; tap the sides to release bubbles.
5. Pull the plug without tilting the pot, let it drain at least 15 minutes, and measure the water that runs out (line B).
6. Air pore space = B divided by A, times 100. Under 15 to 20 percent is the factsheet’s warning zone; 20 to 30 percent is its target for nursery containers.

Water that drained out (line B) (mL)TestAir pore space testPot volume (line A)1 liter (1,000 mL)1 quart (946 mL)2 liters (2,000 mL)1 gallon (3,785 mL)

Air pore space (%)

25.0

Air pore space = drained water / pot volume x 100. Default: 250 mL from a 1 liter pot = 25.0 percent, inside the 20 to 30 percent target; below 15 to 20 percent the Ontario factsheet warns of root dieback and disease.

Run the test on any bag that feels heavy or smells sour, and repeat it on mix you reuse: the Ontario factsheet notes that organic matter breaks into finer particles over a season, which plugs pore space. Whether an old bag is still usable is the subject of our sibling page on whether potting soil goes bad.

Which bag should you buy for pots, raised beds and seed starting?

1. 1Are you starting seeds in cells or flats?

   YesUse a seed-starting mix, the Mulch & Soil Council's separate 'specialty soil' class (for example Miracle-Gro Seed Starting Potting Mix, 0.03-0.03-0.03).

   NoGo to the next question

2. 2Is it going in a pot, window box or hanging basket?

   YesPotting soil or potting mix, either name: buy the bag whose panel lists a peat, coir or bark base plus perlite or pumice and says it is for containers.

   NoGo to the next question

3. 3Are you filling a raised bed?

   YesRaised bed soil or potting mix both work; the deeper column drains better. Compare cost per cubic foot on our garden soil vs potting soil page.

   NoIn-ground bed: mix compost or garden soil into the existing ground instead of potting mix, and soil-test first.

Source: Mulch & Soil Council Uniform Product Guidelines (Sept. 2026) and certified list; maker labels; NC State (1995)

For pots, window boxes and hanging baskets, either name works if the panel shows a peat, coir or bark base plus perlite or pumice and the bag says it is for containers. Raised beds hold a deeper soil column, so the perched water table matters less; the MSC certifies Miracle-Gro Raised Bed Soil and Bonnie Raised Bed Soil in the same premium class as potting mixes, and the cost trade-off for a full bed is worked out on our garden soil vs potting soil page. For seed trays, use a seed starter: the MSC lists Miracle-Gro Seed Starting Potting Mix (0.03-0.03-0.03) under its separate "specialty soils" class.

For in-ground beds, skip both. Potting mixes at about 13 lb per cubic foot (the Miracle-Gro label prints 12.6 lb for 25 quarts) are built to drain in a short column, not to blend into native ground, and a lab soil test tells you what the bed actually lacks. If you are deciding whether bagged material is soil at all, our sibling page on soil vs dirt defines the terms.