Read the bag,
then compare.
Find the intended use, ingredients and directions. Keep both bags beside you and record the same fields.
Updated
The fields to find
- Intended use
- Setting, directions and any restrictions
- Ingredients
- Names and any stated proportions
- Particle grade
- Grade or size range, if stated
- Preparation & additions
- Directions, wetting agent and fertilizer
Find the useful parts of a label.
Illustrative fields to inspect, not a real product label or a suggested formula.
Start with where it will go.
Find the intended use on each bag. Keep its directions beside the comparison.
Ask the supplier: “Is this product intended for the setting I have?”
Washington State University advises a potting mix or potting soil made especially for indoor plants, so the setting named on the bag matters.
Read both ingredient panels.
Copy the component names as printed. Record any proportions the manufacturer supplies.
Ask the supplier: “Can you supply the ingredient information missing from this label?”
Look for soil or sand in the list. Arkansas Extension says soil should be a minor ingredient of modern container mixes, or left out.
Keep the preparation instructions.
Check for a wetting agent or fertilizer already included. Copy the preparation directions for the product you have.
Ask the supplier: “What preparation does this product need before use?”
Purdue says wetting agents help water spread through dry ingredients such as peat, and starter fertilizers supply nutrients at the start. Check whether a finished mix already contains either.
For a missing field, write “not stated” in your notes. Ask for the detail you need before choosing.
Compare your two bags
Copy the same fields from each label. Write “not stated” for missing information; keep your questions with your notes.
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Help with these fields
- Intended use
- For packaged soil amendments, California requires the label to state the product's purpose and directions for use. Check those fields on your bag, and ask the manufacturer when its intended use is unclear.
- Ingredients
- Copy the ingredients in the order printed. In California, packaged soil amendments must list them from the largest amount to the smallest.
- Particle grade
- Iowa State notes that some potting products list traits such as drainage, particle size and water retention.
- Preparation & additions
- Some ingredients need preparing: the University of Florida advises rinsing coir before use because of its salt content.
Still missing a detail? Ask the supplier, and see what a comparison can and cannot settle.
What the front name tells you
Rutgers warns that bag names such as Potting Soil, Container Mix, Garden Soil, Topsoil and Humus are confusing, and says to read the label to learn what is in the bag.
Rutgers says many bagged soil products are entirely organic. Typical ingredients include forest products (“arbor fines”), wood bark, sphagnum or reed-sedge peat, coconut husk fiber (coir) and composts of various kinds and quality.
A 2006 study of retail potting media found differences in physical and chemical properties among brands, and differences in seed germination among bags of one brand.
For the naming question, see potting soil vs potting mix.
Choose a test for the question
Tell the lab whether your sample is mineral soil, potting mix or compost. Rutgers uses a different chemical test for organic growing media than for mineral soil, so one test does not suit every material.
- Acidity and soluble salts
- Rutgers recommends a lab test to check the chemistry of organic growing media. Its saturated-media-extract test differs from the test used for mineral soil.
- Air and water behavior
- Air space, water-holding capacity, total pore space and dry bulk density are physical properties of a growing medium. Purdue describes these properties; ASTM D8593-24 provides a laboratory method for measuring them.
Ask the manufacturer about the recipe or ingredient proportions.
After the bag is opened
The same mix holds far less air when it is packed down. Iowa State reports 15 percent air space when the pot was filled and brushed level, 9 percent after tapping it twice and 4 percent when the mix was pressed down.
In the same mix, a taller pot leaves more of the mix above the wet layer at the bottom. Mixes with smaller pores raise that wet layer.
For questions the label leaves open, see what a comparison can and cannot settle.
Label rules depend on location
Growing-media label rules depend on the state and product category. Georgia registers potting soils and their label information; California specifies label fields for packaged soil amendments.
For a regulatory question, use the agency responsible for the product in your state.