Care basicsHP-05
Houseplant Soil Mix | Basic Ratios, What Each Ingredient Does, Mixes by Plant, and Indoor Soil That Resists Gnats and Mold
A houseplant soil mix starts at 7 parts akadama to 3 parts leaf mold. Indoors, swapping the leaf mold for peat moss makes mold and insects less likely.
In this article (14 sections)
- Conclusion: How Do You Decide on a Houseplant Soil Mix?
- What Does Each Ingredient in a Houseplant Soil Mix Do?
- What Is the Basic Ratio for a Houseplant Soil Mix?
- How Do You Mix Houseplant Soil?
- Does the Houseplant Soil Mix Change by Plant?
- How Do You Choose Bagged "Houseplant Soil"?
- Can You Use Garden or Field Soil in a Houseplant Soil Mix?
- What Houseplant Soil Mix Discourages Fungus Gnats and Mold Indoors?
- What Are the Signs That a Houseplant Soil Mix Needs Rethinking?
- Can Old Houseplant Soil Be Reused?
- How Do You Dispose of Old Houseplant Soil?
- What Terms Come Up in Houseplant Soil Mixes?
Frequently Asked Questions About Houseplant Soil Mixes6
- Jump to this section
- What kind of soil is good for houseplants?
- What ratio should a houseplant soil mix use?
- What should you mix into houseplant soil?
- What soil mix is best for growing houseplants indoors?
- Will houseplants grow in soil from a 100-yen shop?
- What should you do if mold grows on houseplant soil?
- Sources
Conclusion: How Do You Decide on a Houseplant Soil Mix?
Start a houseplant soil mix at 7 parts akadama to 3 parts leaf mold. From there, swap out 20 to 30 percent to suit the plant and where it sits.
In general, houseplant soil needs four properties. Materials from Clemson University in the U.S. list almost the same four.
- Drainage (excess water runs out)
- Water retention (holds the water that roots use)
- Aeration (air reaches the roots)
- Cleanliness (free of insects, disease, and weed seeds)
The tricky part is that drainage and water retention look like opposites. Here is the key. Use granular soil to create gaps, and mix in just a little material that holds water.
| Property needed | Main ingredients that provide it | Sign that it is lacking |
|---|---|---|
| Drainage | Akadama, pumice, perlite, kanuma | The soil stays wet for days after watering |
| Water retention | Leaf mold, peat moss, vermiculite | The pot gets light quickly and leaf tips get damaged |
| Aeration | Evenly sized akadama, pumice, perlite | Roots are brown and soft (root rot) |
| Cleanliness | Inorganic ingredients such as akadama, kanuma, and perlite | Small insects fly over the soil surface |
Here is the order of this article.
- What each ingredient does
- The basic ratio and a ratio for indoors
- Mixes by plant
- How to choose bagged "houseplant soil"
- Soil that discourages fungus gnats and mold
- Reusing and disposing of old soil
Every number comes with a source.
What Does Each Ingredient in a Houseplant Soil Mix Do?
The ingredients in a houseplant soil mix fall into base soils and amendments. Base soils such as akadama form the foundation, and amendments such as leaf mold and perlite add properties.
Hyponex materials describe the properties of each ingredient as follows. Ingredients can also be split into inorganic and organic. Inorganic ones come from minerals and stone, and organic ones come from decomposed plants.
| Ingredient | Type | Main role | Notes on use |
|---|---|---|---|
| Akadama (small grain) | Base soil, inorganic | Good balance of aeration, drainage, water retention, and nutrient retention | As it ages, it produces more fines (powdery soil) |
| Kanuma | Base soil, inorganic | Good aeration and drainage | Acidic. Suits plants that prefer acidic soil |
| Pumice, hyuga pumice | Amendment, inorganic | Very high aeration and drainage | Hyuga pumice holds its shape and can be reused many times |
| Leaf mold | Amendment, organic | Improves aeration, drainage, and nutrient retention | Indoors, it easily becomes a source of mold |
| Peat moss | Amendment, organic | High water retention | Strongly acidic. For indoor use, choose a pH-adjusted product |
| Perlite | Amendment, inorganic | Porous, and raises aeration and drainage | U.S. university materials name it as one source of fluoride |
| Vermiculite | Amendment, inorganic | Light, with excellent water retention and aeration | Add 10 to 20 percent when you want more water retention |
Base soil builds the structure, and amendments fine-tune water retention and aeration. Amendments are not for growing plants on their own. They make up for missing properties.
The fluoride in perlite can turn leaf tips brown in some plants, such as dracaena. For details, see why houseplant leaf tips turn brown.
What Is the Basic Ratio for a Houseplant Soil Mix?
The basic houseplant soil mix is 7 parts akadama (small grain) to 3 parts leaf mold. If you want to keep things clean indoors, use 7 parts akadama to 3 parts peat moss.
The 7 to 3 mix of akadama and leaf mold is commonly called the "golden ratio." Hyponex materials present it as "a mix that many plants grow well in."
Growing guides for monstera, pachira, and Ficus umbellata also recommend the same 7:3.
KINCHO Engei materials give a mix for indoor houseplants that replaces leaf mold with peat moss. The reason is that sterile peat moss helps prevent mold.
| Purpose of the mix | Ratio (by volume) | Source |
|---|---|---|
| Basic (most houseplants) | Small-grain akadama 7 : leaf mold 3 | Hyponex |
| Clean for indoors | Small-grain akadama 7 : peat moss (pH-adjusted) 3 | KINCHO Engei |
| Extra drainage (sansevieria, etc.) | Small-grain akadama 7 : small-grain pumice 3 | Hyponex |
| Lighter weight (hanging pots) | Akadama 3 : peat moss 3 : perlite 2 : vermiculite 2 | KINCHO Engei |
| Soilless mix (U.S. example) | Peat moss 2 : perlite 1 : coarse sand 1 | Clemson University |
| Bark mix (U.S. example) | Fine bark 1 : peat moss 1 : perlite 1 | Cornell University (cited in Clemson University materials) |
U.S. mixes are built around peat moss and do not use akadama. In Japan, akadama is easy to find, so mixes built on akadama are the norm.
From the basic mix, adjust in 10 percent steps, as follows (KINCHO Engei materials).
- For more water retention: add 10 to 20 percent vermiculite
- For better drainage: add about 10 percent hyuga pumice or large-grain perlite
Change only one thing in the mix at a time. Otherwise you won't know which change made the difference.
How Do You Mix Houseplant Soil?
Sift each ingredient to remove the fines, then mix them in the right ratio. If the mix has no fertilizer, add base fertilizer, and let it rest a while before use.
| Step | What to do | Guide and reason |
|---|---|---|
| 1 | Sift each ingredient | Removes fines. Fines hurt drainage and lead to root congestion |
| 2 | Measure and mix in the right ratio | Measure by bulk (volume), not by weight |
| 3 | If there is no fertilizer, mix in base fertilizer | Slow-release granular fertilizer, at the amount on the bag |
| 4 | If you used peat moss that is not pH-adjusted, mix in lime | Peat moss is strongly acidic |
| 5 | Let it rest a while after mixing | Hyponex recommends mixing 1 to 2 months before use and keeping it moist |
| 6 | Store it out of the rain | Close the bag |
The reason to let it rest is that freshly mixed soil has few microbes. Hyponex materials advise keeping it moist so the microbes can multiply.
If you are in a hurry, bagged "houseplant soil" with guaranteed cleanliness is the safer choice. How to choose one is covered two sections below.
Does the Houseplant Soil Mix Change by Plant?
Yes. Sansevieria needs extra drainage, while monstera and pachira grow well in the basic 7:3.
A houseplant soil mix is decided by how much water the plant likes. The table lists the mixes given in manufacturers' growing guides, plant by plant.
| Plant | Mix given by the manufacturer | Notes | Source |
|---|---|---|---|
| Monstera | Akadama 7 : leaf mold 3 | Repot from May to September, once every two years | Hyponex |
| Pachira | Small-grain akadama 7 : leaf mold 3 | Root rot is the most common reason it dies | Hyponex |
| Pothos | Base soil plus leaf mold or similar | No ratio given. 7:3 is a starting point | Hyponex |
| Ficus microcarpa | A blend of kanuma or akadama, or bagged soil | No ratio given | Hyponex |
| Sansevieria | Small-grain akadama 7 : small-grain pumice 3 | A mix with no organic matter. Does not tolerate soggy soil | Hyponex |
| Ficus umbellata | Base soil 7 : leaf mold or similar 3 | Bagged houseplant soil also works | Hyponex |
Sansevieria is the only one with no organic matter in its mix. Hyponex materials describe sansevieria as "weak to excess moisture."
If you use bagged soil, products containing small-grain akadama, bark compost, and kanuma are recommended.
| Plant | Snake plant (Dracaena trifasciata) |
|---|---|
| Light | Bright; tolerates low light |
| Watering | Sparingly; about monthly in winter |
| Winter minimum (guide) | 10 |
| Humidity | Low is fine |
| Repotting | May to Aug, every 1 to 3 years (sources vary) |
| Toxic to pets (ASPCA) | Yes (saponins) |
Source: Hyponex Plantia care guides, RHS hardiness ratings, ASPCA toxic plant list
Philodendron belongs to the same aroid family as monstera and pothos. In the U.S., mixes with bark are used for it. It is the Cornell University mix that appears in Clemson University materials.
Watering frequency and repotting time also differ by plant. Look at them together when you choose a mix.
| Plant | Watering | Repotting |
|---|---|---|
| Monstera deliciosa | When the top of the soil is dry; less in winter | May to Sep, every 2 years |
| Pachira aquatica (money tree) | Soak when dry; less in winter | Apr to Jun or Sep, every 1 to 2 years |
| Pothos (Epipremnum aureum) | When the top is dry | May to Aug, every 2 to 3 years |
| Ficus microcarpa | When dry; less in winter | May to Jun, every 1 to 2 years |
| Snake plant (Dracaena trifasciata) | Sparingly; about monthly in winter | May to Aug, every 1 to 3 years (sources vary) |
Source: Hyponex Plantia care guides, RHS hardiness ratings, ASPCA toxic plant list
How Do You Choose Bagged "Houseplant Soil"?
Check the bag label for the ingredients, whether fertilizer is included, and pH adjustment. Soil with even grains and few fines is less likely to cause root rot.
In general, bagged potting mixes are made from clean soil. Hyponex materials also say they are "less prone to disease."
The trouble is that every bag says "houseplant soil," so it is hard to tell them apart. KINCHO Engei materials advise checking the following on the label.
| What to check on the bag | Why | When to step in |
|---|---|---|
| Intended plants | Whether the mix is made for houseplants | If it is for flowering plants, check the drainage |
| Main ingredients | How much organic matter (leaf mold, compost) it has | If it will be indoors, cover the surface with an inorganic material |
| Fertilizer | Whether you need to add base fertilizer | If none is included, mix in base fertilizer |
| pH adjustment | Peat moss is strongly acidic | If not adjusted, mix in lime |
| Grain size and fines | Directly affect drainage | Avoid soil with lots of fines |
| Manufacturer | Whether you can ask about the contents | Avoid bags with little information |
Choose by what the label says, not by price. You can judge soil from 100-yen shops by the same standards.
Soil with uneven grains and lots of fines drains poorly and causes root rot. This warning comes from KINCHO Engei materials.
Can You Use Garden or Field Soil in a Houseplant Soil Mix?
As a rule, no. Garden soil packs down in a pot, and it also contains bacteria and insects.
University of Maryland materials explain why garden soil should not go in pots.
- The soil is fine and dense, so air and water move poorly in a pot
- Water stays in the tiny gaps, leaving the roots sitting in water
Clemson University materials also say garden soil contains many bacteria and is not recommended for pots.
If you do use it, first heat it to kill pathogens and insects. Then, the materials say, mix in bark or peat moss. For indoor houseplants, bagged ingredients are less work.
From the top, a pot holds a gap where water pools (the water space), then the soil, then the pot bottom. University of Wisconsin materials say the pot must always have holes in the bottom.
When you use a decorative cover pot without holes, set the pot with holes inside it and check that no water collects at the bottom. This is the "double potting" method from the same materials.
What Houseplant Soil Mix Discourages Fungus Gnats and Mold Indoors?
Use a mix with less organic matter and let the soil surface dry. Covering the surface with an inorganic material such as akadama also works.
The small insects that appear in indoor potting soil include fungus gnats. U.S. university materials say the larvae live near the soil surface.
North Carolina State University materials describe the soil where they multiply easily.
- Soil that is always moist
- Soil with too much decaying plant material or organic matter
The remedies come from the same materials and from Cornell University materials.
| Remedy | How | Aim |
|---|---|---|
| Dry the surface | Let the top 2.5 cm or so dry between waterings | Fewer eggs are laid, and larvae struggle to develop |
| Cut back organic matter | Avoid soil heavy in leaf mold or compost. For sansevieria, use inorganic material only | Less organic matter for larvae to grow in |
| Cover the surface | Cover with coarse sand, small-grain akadama, or pumice | Blocks the places where eggs are laid |
| Water from below | Let the pot soak it up from the saucer without wetting the surface | Keeps the surface dry |
| Trap the adults | Set out yellow sticky cards | Fewer adults to lay eggs |
For both insects and mold, the shared cause is a soil surface that is always moist. Before changing the mix, first rethink how often you water.
If soil with leaf mold is giving you trouble, try covering the surface with small-grain akadama. It is easier than repotting.
White material on the soil surface comes in two kinds. Clemson University materials tell them apart as follows.
| What you see | What it is | What to do |
|---|---|---|
| A hard white to gray crust on the surface or the pot rim | Fertilizer salts (fertilizer components that have hardened) | Remove the crust and add fresh soil. Flush with water |
| Fluffy white to yellow growth on the surface | Fungi that break down dead matter (saprophytic fungi) | Let the surface dry. It is a sign of too much moisture |
| White grains mixed into the soil | Usually perlite (a white granular ingredient) | Leave it as is |
Iowa State University materials discuss similar mold on seedling pots. It looks bad but does not hurt healthy seedlings, and it is a sign of too much moisture.
What Are the Signs That a Houseplant Soil Mix Needs Rethinking?
There are three: water soaks in slowly, the soil stays wet for days, or roots come out of the bottom of the pot. If you see any of them, repot with fresh soil.
Over time, the grains in houseplant soil break down and the fines increase. Drainage and aeration drop, so the time comes to rethink the mix.
| Sign | Likely cause | What to do |
|---|---|---|
| Water pools on the surface and is slow to soak in | More fines, or the pot is full of roots | Repot with fresh soil |
| Days after watering, the soil is still moist 3 cm down when you test with a finger | A poorly draining mix | Switch to soil with added pumice or large-grain perlite |
| Roots are coming out of the drainage hole | Rootbound | Repot into a pot one size larger |
| There is a white crust on the surface | Fertilizer salts have built up | Replace the top layer of soil and flush with water |
Repotting timing and steps are in repotting houseplants. If the soil stays wet and the roots are damaged, read the root rot article first.
Can Old Houseplant Soil Be Reused?
Yes. But it is safer not to reuse soil from a pot that had root rot or disease.
Left as is, old soil has less organic matter and may harbor pests or disease. KINCHO Engei materials say it can be reused with some work.
| Step | What to do | Guide | Source |
|---|---|---|---|
| 1 | Remove old roots and debris, spread the soil out, and dry it | Sun-dry for 1 week in summer, 2 weeks in winter | KINCHO Engei |
| 2 | Sift out the fines | Use a 7 to 10 mm sieve to remove debris. Discard the fine dust too | Sakata Seed, Hyponex |
| 3 | In summer, disinfect it with sunlight | Moisten it, put it in a black plastic bag, and leave it in the sun | KINCHO Engei, Hyponex |
| 4 | In winter, disinfect it with cold | Pour boiling water over it and leave it outdoors in the frost and cold | Hyponex |
| 5 | Mix in new ingredients | About 20 to 30 percent leaf mold and about 10 percent akadama | KINCHO Engei |
| 6 | Add base fertilizer and lime | Amounts suited to the next plant | KINCHO Engei |
Sources differ on how many days of sun disinfection are needed. KINCHO Engei says 2 to 3 days, while Hyponex says to turn the bag over once a week.
University of Maryland materials describe mixing old and new soil half and half. They say not to reuse soil where root disease appeared.
Do not mix in unfermented kitchen scraps or fallen leaves. Hyponex materials say the heat of fermentation damages roots.
How Do You Dispose of Old Houseplant Soil?
First check your local government's garbage guide. Many municipalities do not collect soil, and in that case you can use a collection company or a store's take-back service.
According to Hyponex materials, how soil is handled differs by municipality. Some areas accept it as non-burnable garbage, while others refer you to a specialized collection company.
| Method | What to check |
|---|---|
| Municipal garbage | The sorting rules for "soil, sand, and stones." The limit on how much you can put out |
| Collection company | Collection units and fees |
| Store soil take-back | Collection boxes at home improvement stores. Whether your store takes part |
| Recycle and reuse | Recycle it with the steps above. Not for soil that had disease |
Before throwing it out, first consider whether you can recycle it for your next repotting. If you can, you save both the work of disposal and the cost of new soil.
If you are unsure how to dispose of it, look up "soil" in your local government's garbage sorting guide. The wording differs by area.
What Terms Come Up in Houseplant Soil Mixes?
| Term | Meaning |
|---|---|
| Base soil | The soil that forms the foundation of a mix, such as akadama and kanuma |
| Amendment | A material that adds properties, such as leaf mold, peat moss, perlite, and vermiculite |
| Potting mix | Ready-to-use soil with the ingredients and fertilizer already mixed in |
| Inorganic ingredient | Made from minerals or stone. Rarely a source of insects or mold |
| Organic ingredient | Made from decomposed plants. Raises water and nutrient retention |
| Fines | Powdery soil from broken-down grains. Hurts drainage |
| Base fertilizer | Fertilizer mixed into the soil at planting time |
| Acidity (pH) | How acidic or alkaline the soil is. Peat moss and kanuma are acidic |
| Saprophytic fungi | Fungi that break down dead matter. Often the fluffy white growth on the soil surface |
| Water space | The gap between the pot rim and the soil surface, where water collects briefly when you water |
Frequently Asked Questions About Houseplant Soil Mixes
What kind of soil is good for houseplants?
Soil that has all four: drainage, water retention, aeration, and cleanliness. Using akadama as the base and mixing in 30 percent leaf mold or peat moss balances all four.
Indoors, put cleanliness first and keep organic matter low. Bagged "houseplant soil" is also a reliable way to get clean soil.
What ratio should a houseplant soil mix use?
The basic mix is 7 parts akadama (small grain) to 3 parts leaf mold. Indoors, use 7 parts akadama to 3 parts peat moss.
For plants that need little water, such as sansevieria, use 7 parts akadama to 3 parts pumice. If unsure, start at 7:3, watch how fast it dries, and adjust 10 percent at a time.
What should you mix into houseplant soil?
Mix leaf mold or peat moss into akadama. For more drainage, add pumice or perlite, and for more water retention, add vermiculite.
Add about 10 to 20 percent. Use amendments only to make up for missing properties.
What soil mix is best for growing houseplants indoors?
7 parts akadama (small grain) to 3 parts peat moss (pH-adjusted). KINCHO Engei materials list it as a mix that prevents mold.
Covering the surface with small-grain akadama also discourages fungus gnats. And remember to let the surface dry between waterings.
Will houseplants grow in soil from a 100-yen shop?
Whether they grow depends on the bag label, not the price. Judge by the ingredients, whether fertilizer is included, pH adjustment, and how many fines it has.
Soil with lots of fines and uneven grains drains poorly and causes root rot. If you are concerned, sift it before use.
What should you do if mold grows on houseplant soil?
Fluffy white growth on the surface is usually fungi that break down dead matter. Remove the surface layer and keep the soil on the dry side.
Mold is a sign of "too much moisture," so rethink how often you water. If it is a hard white crust, it is fertilizer salts, not mold.
Care basicsWhen Should You Repot Houseplants? Month and Plant Charts, Signs, Steps and AftercareRepot houseplants in May to September, when they grow at 15°C or above. Month and plant charts, signs, tools and steps, pot choice, aftercare and winter repotting.
Find by symptomHow to Revive a Houseplant with Root Rot | Signs Before Unpotting, Root Color and Firmness, and Rescue by PlantHouseplant root rot can be reversed if white, firm roots remain. Signs before unpotting, root color, where to cut, soil and pot, rescue by plant, and a checklist.Find by symptomBrown Leaf Tips on Houseplants | Find the Cause from How the Brown Appears, Prevent It by Plant, and Trim Dead TipsHouseplant leaf tips turn brown from dry air, underwatering, fertilizer salts, water chemistry, rootbinding, or AC drafts. Diagnose by pattern, trim, and prevent.
Find by symptomWhy Houseplant Leaves Turn Yellow | Identify the Cause by Which Leaves Yellow First, Then Treat It by Plant and SeasonWhere yellowing starts narrows the cause. Covers Monstera, Pachira, Pothos, Ficus and Sansevieria, summer, winter and repotting, recovery odds and what to avoid.Sources
- Hyponex Plantia: Explaining Potting Soil! How to Make and Use It, Differences from Leaf Mold (in Japanese. 7:3 Ratio, Role of Each Ingredient, Resting Period)
- Hyponex Plantia: How to Dispose of Old Soil? Is There a Way to Recycle It? (in Japanese)
- Hyponex Plantia: How to Grow Monstera (in Japanese)
- Hyponex Plantia: How to Grow Pachira | Is Watering Why It Dies? (in Japanese)
- Hyponex Plantia: How to Grow Pothos (in Japanese)
- Hyponex Plantia: How to Grow Ficus Microcarpa, or Gajumaru (in Japanese)
- Hyponex Plantia: How to Grow and Repot Sansevieria (in Japanese)
- Hyponex Plantia: How to Grow Ficus Umbellata (in Japanese)
- Hyponex: How to Grow Monstera and Growing Tips (in Japanese. Repotting Time)
- Hyponex: How to Grow Sansevieria and Growing Tips (in Japanese. Weak to Excess Moisture)
- KINCHO Engei: 3-7. Making Soil for Growing Flowers and Flowering Trees in Containers (in Japanese. Indoor Mix, Choosing Bagged Soil, Old Soil)
- KINCHO Engei: 3-4. Blending Soil to Suit Your Growing Purpose (in Japanese)
- KINCHO Engei Q&A: How Can I Reuse Potting Soil? (in Japanese)
- Sakata Seed FAQ: How to Reuse Soil from Pots and Planters (in Japanese)
- Clemson University HGIC: Indoor Plants: Soil Mixes (Properties Needed, Garden Soil, Example Mixes)
- Clemson University HGIC: Houseplant Diseases & Disorders (Telling Fertilizer Salt Crust from Saprophytic Fungi)
- University of Maryland Extension: Growing Media (Potting Soil) for Containers (Garden Soil, Reusing Old Soil)
- University of Wisconsin-Madison Extension: Healthy Roots, Healthy Houseplants (Perlite, Drainage Holes, Double Potting)
- NC State Extension: Fungus Gnats: Tiny Pests in Houseplants and How to Control Them
- Cornell Cooperative Extension Allegany County: A Spooky Houseplant Pest: Fungus Gnats
- Iowa State University Extension: Will mold on peat pots harm my flower and vegetable seedlings?
- Michigan State University Extension: Fluoride toxicity in plants irrigated with city water (Fluoride in Perlite)