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Potting soil or growing media, also known as potting mix or potting compost (UK), is a substrate used to grow plants in containers. The first recorded use of the term is from an 1861 issue of the American Agriculturist.^[1] Despite its name, little or no soil is usually used in potting soil.

Materials

Materials used for growing mediums include: peat, coconut coir, wood products like bark and wood fiber, perlite, stone wool, soils/tufts, and recycled paper and cardboard.^[2] Other materials used include rice hulls, sand, vermiculite, and calcined clays.^[3]

Properties

Typical potting mixes include one or more materials which retain moisture, one or more materials which aid in aeration and drainage, and fertilizer. Moisture-retaining materials and aerating materials can be combined in any ratio, depending on the particular needs of the plant. Soils are minimally used as growing media because they compact and lose pore space after repeated watering and can be too heavy for growing potted plants.^[4] Mediums used for growing plants in pots typically are a mix of organic and inorganic ingredients.^[5]

Good growing mediums have a number of properties including moisture and nutrient retention capacity, quick water infiltration, pore space for aeration (plants roots need oxygen), drainage for excess water, decompose slowly, and provide support for the plants growing in them.^[5] They also have an optimal range of pH, cation exchange properties, and lack substance that are toxic to plants ^[5] These are also dependent on the type of plant grown since there is wide variation in moisture and nutrient needs among different plants.

Moisture retention

This part is usually made up of peat (usually with limestone to reduce acidity)^[6] or coconut coir. It serves to absorb water and nutrients. Tree bark, mainly of pine, may also be used.

The use of peat is controversial since the harvesting of peat moss from peatlands (which includes unique habitats such as bogs and fens) can degrade these peatlands. Peatlands are home to a diverse range of plant and animal species. Peat also has a very slow accumulation rate, as little as 1mm per year, so they take a long time to regenerate. Peatlands are also carbon sinks, constituting 3% of the world's surface but storing up to 30% of the carbon sequestered in the soil.^[7] The removal of the layer of CO₂ absorbing plants releases CO₂ into the atmosphere, contributing to climate change.^[8]^[9]

As such, alternatives such as coconut coir are promoted by some organisations.^[10]^[11]

Drainage

Sand and grit may be used for drainage and aeration. Perlite and vermiculite improve both aeration and water retention.

Nutrients and chemistry

All plants need essential plant nutrients to grow, so it is important to make sure there is a sufficient amount in the potting soil.^[12] Some nutrients may be already present in the bulking ingredients.^[13] Peat contains 1% nitrogen that is almost never released. Limestone (for raising pH) contains mostly calcium (calcite), but can also contain magnesium (dolomitic). The latter is preferred as it supplies both elements. A typical proportion of limestone to peat is 8.5 pounds per cubic yard (5.0 kg/m³).^[13] Coir contains a high amount of electrolytes (salts). In fact, untreated coir contains too much sodium and potassium for plant growth, so it is washed and then buffered (partially replacing salts with other minerals, usually calcium and magnesium) to produce the growth medium. Vermiculite contains some calcium and magnesium, but more importantly it helps retain water and nutrients in the porous structure.

Nutrients not supplied by the bulk will need to be supplied by the fertilizer. In conventional mixes they may be slow-release formulae of synthetic fertilizers, while organic mixes will use organic source such as compost (e.g. leaf mold, bark compost or recycled mushroom compost). Overuse of fertilizers will, as with in normal soils, risk damaging the plant.^[13] For compost, the maximum recommended amount is 1 part compost to 1 part bulking material.^[14]

A soil test may be done to analyze the chemistry of a potting mix, despite the mix not necessarily being made of soil. As an approximation for indoor home planting, the mix is generally treated as greenhouse growth medium. The main method is a saturated media extract (SME), which tests the chemical contents of a water extract of the mix.^[13]^[15]

Reference levels for potting mix by the SME method^[13]^[a]
Analysis	Acceptable, min	Optimum, min	Optimum, max	Acceptable, max
Soluble salt, mS/cm^[b]	0.75	2.0	3.5	5.0
Nitrate-N, ppm^[c]	40	100	200	299
Phosphorus, ppm	3	6	9	18
Calcium, ppm	80	200	—	—
Magnesium, ppm	30	70	—	—

Different mixes for different uses

The growth medium should be adapted to each plant's (and growth stage's) preference for aeration, drainage, nutrition, and pH.^[14]

For seed starting, a "germination mix" is typically light-weight and suitable for starting small-seeded plants. A "seed starting" mix is suitable for larger seeded crops.^[17] Following early growth, most plants prefer a potting mix that is more well-draining.

Cacti and succulents require sharp drainage, thus requiring a much larger percentage of perlite or sand.^[18] Carnivorous plants, such as the Venus flytrap and the pitcher plant, prefer the nutrient-poor, acidic soils common to bogs and fens,^[19] while water-based plants thrive in a heavier topsoil mix.^[20]

Sterilization

Commercially available potting soil is sterilized, in order to avoid the spread of weeds and plant-borne diseases.^[21]

As with garden soil, potting soil can attract insects. For example, the fungus gnat is often found around houseplants because it lays eggs in moist potting soil.^[22]

Infections of Legionnaires' disease due to potting mix have been reported in Australia,^[23] New Zealand,^[24] the Netherlands,^[25] the United States,^[26] and Japan.^[27]

References

^ UVM data from the 1980s. An extended and updated (~1995) version of this table may be found from UConn.^[16] Significant variation in reference ranges is possible due to procedural differences, so it is recommended to use the test provider's values.
^ May be also written mmhos/cm using the "mho" synonym of S (siemens).
^ Generally written mg/L in newer sources.

^ Oxford English Dictionary
^ Jackson, Brian (November 2022). "Current and Future State of the Growing Media Industry" (PDF). Greenhouse Grower (November, 2022): 20–24. Retrieved 2024-06-17.
^ "Growing Media - Ornamental Production Ornamental Production". aggie-horticulture.tamu.edu. Retrieved 2022-11-11.
^ Pleasant, Barbara. "The Complete Houseplant Survival Guide." Pages 314. Storey Publishing. ISBN 1-58017-569-4
^ ^a ^b ^c Arteca, Richard N. (2014-02-14). Introduction to Horticultural Science. Cengage Learning. ISBN 978-1-305-17780-2.
^ Nissen, Dante. "The Indoor Plant Bible." Page 21. Barron’s. ISBN 0-7641-5769-8
^ "Serious about climate change? Get serious about peat". Washington Post. 2021-11-10. Retrieved 2022-07-26.
^ Gardeners urged to stop using peat-based compost
^ Peat moss: Good for plants but bad for the planet?
^ Peat alternatives in the garden
^ Alternatives to peat
^ Leichty, Corey. "Does Potting Soil Need Fertilizer?". Do Not Disturb Gardening.
^ ^a ^b ^c ^d ^e "pottingmix". www.uvm.edu.
^ ^a ^b What is Potting Soil?
^ "Methods of Greenhouse Media Testing and How They Differ". Center for Agriculture, Food, and the Environment. 6 March 2015.
^ Dawn Pettinelli, Extension Educator and Dr. Richard McAvoy. "Interpretation of SME Results for Greenhouse Media" (PDF). Soil Nutrient Analysis Laboratory, University of Connecticut.
^ "Guidelines for Starting Seeds Indoors, from Johnny's Research Team". www.johnnyseeds.com. Retrieved 2021-01-19.
^ Burne, Geoffrey. "Encyclopedia of Container Gardening." Page 22. Fog City Press. ISBN 978-1-877019-43-2
^ "Dirty Buttons - Arts and Culture - Philly Weekly". philadelphiaweekly.com. Archived from the original on 2012-09-07.
^ "Creating a water garden in a tub". The Christian Science Monitor.
^ Carol Cloud Bailey. "Carol Cloud Bailey: Heat potting soil to prepare it for replanting". TCP. Archived from the original on 2016-05-30. Retrieved 2016-05-30.
^ "How to minimize dents in carpet from furniture". azcentral.com.
^ Speers DJ, Tribe AE (October 1994). "Legionella longbeachae pneumonia associated with potting mix". Med. J. Aust. 161 (8): 509. doi:10.5694/j.1326-5377.1994.tb127576.x. PMID 7935133. S2CID 28552691.
^ Kingston M, Padwell A (March 1994). "Fatal legionellosis from gardening". N. Z. Med. J. 107 (974): 111. PMID 8127508.
^ den Boer, JW; Yzerman, EP; Jansen, R; Bruin, JP; Verhoef, LP; Neve, G; van der Zwaluw, K (January 2007). "Legionnaires' disease and gardening". Clin. Microbiol. Infect. 13 (1): 88–91. doi:10.1111/j.1469-0691.2006.01562.x. PMID 17184293.
^ "Legionnaires' disease associated with potting soil--California, Oregon, and Washington, May-June 2000". Can. Commun. Dis. Rep. 26 (22): 189–92. November 2000. PMID 11131692.
^ "Legionnaires' Disease Associated with Potting Soil --- California, Oregon, and Washington, May--June 2000". Centers for Disease Control and Prevention.

[17] UVM data from the 1980s. An extended and updated (~1995) version of this table may be found from UConn.^[16] Significant variation in reference ranges is possible due to procedural differences, so it is recommended to use the test provider's values.

[18] May be also written mmhos/cm using the "mho" synonym of S (siemens).

[19] Generally written mg/L in newer sources.

[1] Oxford English Dictionary

[2] Jackson, Brian (November 2022). "Current and Future State of the Growing Media Industry" (PDF). Greenhouse Grower (November, 2022): 20–24. Retrieved 2024-06-17.

[3] "Growing Media - Ornamental Production Ornamental Production". aggie-horticulture.tamu.edu. Retrieved 2022-11-11.

[4] Pleasant, Barbara. "The Complete Houseplant Survival Guide." Pages 314. Storey Publishing. ISBN 1-58017-569-4

[Arteca-5] Arteca, Richard N. (2014-02-14). Introduction to Horticultural Science. Cengage Learning. ISBN 978-1-305-17780-2.

[6] Nissen, Dante. "The Indoor Plant Bible." Page 21. Barron’s. ISBN 0-7641-5769-8

[7] "Serious about climate change? Get serious about peat". Washington Post. 2021-11-10. Retrieved 2022-07-26.

[8] Gardeners urged to stop using peat-based compost

[9] Peat moss: Good for plants but bad for the planet?

[10] Peat alternatives in the garden

[11] Alternatives to peat

[12] Leichty, Corey. "Does Potting Soil Need Fertilizer?". Do Not Disturb Gardening.

[uvm-13] "pottingmix". www.uvm.edu.

[grank-14] What is Potting Soil?

[15] "Methods of Greenhouse Media Testing and How They Differ". Center for Agriculture, Food, and the Environment. 6 March 2015.

[16] Dawn Pettinelli, Extension Educator and Dr. Richard McAvoy. "Interpretation of SME Results for Greenhouse Media" (PDF). Soil Nutrient Analysis Laboratory, University of Connecticut.

[20] "Guidelines for Starting Seeds Indoors, from Johnny's Research Team". www.johnnyseeds.com. Retrieved 2021-01-19.

[21] Burne, Geoffrey. "Encyclopedia of Container Gardening." Page 22. Fog City Press. ISBN 978-1-877019-43-2

[22] "Dirty Buttons - Arts and Culture - Philly Weekly". philadelphiaweekly.com. Archived from the original on 2012-09-07.

[23] "Creating a water garden in a tub". The Christian Science Monitor.

[24] Carol Cloud Bailey. "Carol Cloud Bailey: Heat potting soil to prepare it for replanting". TCP. Archived from the original on 2016-05-30. Retrieved 2016-05-30.

[25] "How to minimize dents in carpet from furniture". azcentral.com.

[26] Speers DJ, Tribe AE (October 1994). "Legionella longbeachae pneumonia associated with potting mix". Med. J. Aust. 161 (8): 509. doi:10.5694/j.1326-5377.1994.tb127576.x. PMID 7935133. S2CID 28552691.

[27] Kingston M, Padwell A (March 1994). "Fatal legionellosis from gardening". N. Z. Med. J. 107 (974): 111. PMID 8127508.

[28] Boer, JW; Yzerman, EP; Jansen, R; Bruin, JP; Verhoef, LP; Neve, G; van der Zwaluw, K (January 2007). "Legionnaires' disease and gardening". Clin. Microbiol. Infect. 13 (1): 88–91. doi:10.1111/j.1469-0691.2006.01562.x. PMID 17184293.

[29] "Legionnaires' disease associated with potting soil--California, Oregon, and Washington, May-June 2000". Can. Commun. Dis. Rep. 26 (22): 189–92. November 2000. PMID 11131692.

[30] "Legionnaires' Disease Associated with Potting Soil --- California, Oregon, and Washington, May--June 2000". Centers for Disease Control and Prevention.

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@@ Line 2: / Line 2: @@
 [[File:Potting soil.jpg|250px|right|thumb|A flowerpot filled with potting soil]]
-'''Potting soil''', also known as '''potting mix''' or '''miracle soil''', is a medium in which to grow plants, herbs and vegetables in a  pot or other durable container. The first recorded use of the term is from an 1861 issue of the ''American Agriculturist''.<ref>[http://dictionary.oed.com/cgi/entry/50185534/50185534se9?single=1&query_type=word&queryword=potting+soil&first=1&max_to_show=10&hilite=50185534se9 Oxford English Dictionary]</ref>
+'''Potting soil''' or '''growing media''', also known as '''potting mix''' or '''potting compost''' (UK), is a [[substrate (biology)|substrate]] used to grow plants in containers. The first recorded use of the term is from an 1861 issue of the ''American Agriculturist''.<ref>[http://dictionary.oed.com/cgi/entry/50185534/50185534se9?single=1&query_type=word&queryword=potting+soil&first=1&max_to_show=10&hilite=50185534se9 Oxford English Dictionary]</ref> Despite its name, little or no [[soil]] is usually used in potting soil.
-==Ingredients==
+==Materials==
+Materials used for growing mediums include: [[peat]], coconut coir, wood products like bark and wood fiber, [[perlite]], [[Mineral wool|stone wool]], soils/tufts, and recycled paper and cardboard.<ref>{{Cite journal |last=Jackson |first=Brian |date=November 2022 |title=Current and Future State of the Growing Media Industry |journal=Greenhouse Grower |issue=November, 2022 |pages=20–24 |url=https://woodsubstrates.cals.ncsu.edu/wp-content/uploads/sites/147/2023/01/82-popular-press.pdf |access-date=2024-06-17}}</ref> Other materials used include rice hulls, sand, [[vermiculite]], and calcined clays.<ref>{{Cite web |title=Growing Media - Ornamental Production Ornamental Production |url=https://aggie-horticulture.tamu.edu/ornamental/greenhouse-management/growing-media/ |access-date=2022-11-11 |website=aggie-horticulture.tamu.edu}}</ref>
-Most commonly, potting soil is either [[peat]]  moss (with limestone<ref>Nissen, Dante. "The Indoor Plant Bible." Page 21. Barron’s. {{ISBN|0-7641-5769-8}}</ref><!-- The limestone is added to to increase the pH as peat itself is too acidic for most plants-->)-based or [[Coconut#Coir|coconut coir]]-based.
+==Properties==
-Additional ingredients used in the mix may include [[sand]], [[perlite]], and [[wikt:grit|grit]] (for improving drainage) and [[vermiculite]] (to increase water retention).
+Typical potting mixes include one or more materials which retain moisture, one or more materials which aid in aeration and drainage, and fertilizer. Moisture-retaining materials and aerating materials can be combined in any ratio, depending on the particular needs of the plant. Soils are minimally used as growing media because they compact and lose [[Pore space in soil|pore space]] after repeated watering and can be too heavy for growing potted plants.<ref>Pleasant, Barbara. "The Complete Houseplant Survival Guide." Pages 314. Storey Publishing. {{ISBN|1-58017-569-4}}</ref> Mediums used for growing plants in pots typically are a mix of organic and inorganic ingredients.<ref name="Arteca">{{Cite book |last=Arteca |first=Richard N. |url=https://books.google.com/books?id=84XAAgAAQBAJ&pg=PA339 |title=Introduction to Horticultural Science |date=2014-02-14 |publisher=Cengage Learning |isbn=978-1-305-17780-2 |language=en}}</ref>
+Good growing mediums have a number of properties including moisture and nutrient retention capacity, quick water infiltration, pore space for aeration (plants [[root]]s need oxygen), drainage for excess water, decompose slowly, and provide support for the plants growing in them.<ref name="Arteca"/> They also have an optimal range of pH, cation exchange properties, and lack substance that are toxic to plants <ref name="Arteca"/> These are also dependent on the type of plant grown since there is wide variation in moisture and nutrient needs among different plants.
-Fertiliser (in the form of [[compost]]; i.e. leaf mold, [[Bark (botany)|bark]] compost or recycled mushroom compost) is generally not added (or only in very small quantities) for potting soil used for cuttings and seedlings as large amounts of fertiliser are too aggressive for them. It is used for larger plants (larger pots) though.
+=== Moisture retention ===
-Despite its name, little or no [[soil]] is used in potting soil because it is considered too heavy for growing houseplants.<ref>Pleasant, Barbara. "The Complete Houseplant Survival Guide." Pages 314. Storey Publishing. {{ISBN|1-58017-569-4}}</ref>
+This part is usually made up of [[peat]] (usually with [[limestone]] to reduce acidity)<ref>Nissen, Dante. "The Indoor Plant Bible." Page 21. Barron’s. {{ISBN|0-7641-5769-8}}</ref> or coconut [[coir]]. It serves to absorb water and nutrients. [[Tree bark]], mainly of pine, may also be used.
+The use of peat [[Peat#Environmental and ecological issues|is controversial]] since the harvesting of peat moss from [[peatland]]s (which includes unique habitats such as bogs and fens) can degrade these peatlands. Peatlands are home to a diverse range of plant and animal species. Peat also has a very slow accumulation rate, as little as 1mm per year, so they take a long time to regenerate. Peatlands are also carbon sinks, constituting 3% of the world's surface but storing up to 30% of the carbon sequestered in the soil.<ref>{{Cite news |date=2021-11-10 |title=Serious about climate change? Get serious about peat. |url=https://www.washingtonpost.com/world/2021/11/10/cop26-peat-carbon/ |access-date=2022-07-26 |newspaper=Washington Post |language=en}}</ref> The removal of the layer of {{CO2}} absorbing plants releases {{CO2}} into the atmosphere, contributing to climate change.<ref>[https://www.independent.co.uk/environment/green-living/gardeners-urged-to-stop-using-peat-based-compost-1918355.html Gardeners urged to stop using peat-based compost]</ref><ref>[https://www.washingtonpost.com/lifestyle/home/should-sustainable-gardeners-use-peat-moss/2017/05/09/1fc746f0-3118-11e7-9534-00e4656c22aa_story.html Peat moss: Good for plants but bad for the planet?]</ref>
-=== Peat ===
-{{Main|Peat#Environmental and ecological issues}}
-The use of peat is [[controversial]] since the harvesting of peat moss from [[peatland]]s (which includes unique habitats such as bogs and fens) degrades these peatlands. Peatlands are home to a diverse range of plant and animal species. Peat also has a very slow accumulation rate, as little as 1mm per year, so they take a long time to regenerate. Also, the removal of the layer of CO2 absorbing plants releases CO2 into the atmosphere, contributing to climate change.<ref>[https://www.independent.co.uk/environment/green-living/gardeners-urged-to-stop-using-peat-based-compost-1918355.html Gardeners urged to stop using peat-based compost]</ref><ref>[https://www.washingtonpost.com/lifestyle/home/should-sustainable-gardeners-use-peat-moss/2017/05/09/1fc746f0-3118-11e7-9534-00e4656c22aa_story.html Peat moss: Good for plants but bad for the planet?]</ref>
 As such, alternatives such as coconut [[coir]] are promoted by some organisations.<ref>[https://www.gardenersworld.com/plants/alternatives-to-peat/ Peat alternatives in the garden]</ref><ref>[https://www.rhs.org.uk/science/gardening-in-a-changing-world/peat-use-in-gardens/peat-alternatives Alternatives to peat]</ref>
+=== Drainage ===
-==Different mixes for different uses and plants==
+[[Sand]] and [[wikt:grit|grit]] may be used for drainage and aeration. [[Perlite]] and [[vermiculite]] improve both aeration and water retention.
-For seed starting and cuttings, a mix can be made using 40% coconut coir or peat moss with limestone, 40% vermiculite, and 20% sand.<ref>[https://savvygardening.com/diy-potting-soil/ DIY Potting Soil: 6 Homemade Potting Mixes]</ref> Besides sand, it is also possible to use perlite, using near-similar sized percentages (33%-33%-33%).<ref>[https://www.gardenbetty.com/how-to-make-your-own-seed-starting-and-potting-mix/ 3-ingredient seed starting mix]</ref> For seed starting, a "germination mix" is typically light-weight and suitable for starting small-seeded plants. A "seed starting" mix is suitable for larger seeded crops.<ref>{{Cite web|title=Guidelines for Starting Seeds Indoors, from Johnny's Research Team|url=https://www.johnnyseeds.com/growers-library/tools-supplies/seed-starting-transplanting-guidelines.html|access-date=2021-01-19|website=www.johnnyseeds.com}}</ref>  <!--Sand is best riversand, with a grain size of 2mm or less--> Following early growth, most plants prefer a potting mix that is more well-draining, often with less than 20% of peat moss or other fine-grained materials.
+=== Nutrients and chemistry ===
-Plants also require potting soil<ref>[https://gardenranker.com/what-is-potting-soil/ What is Potting Soil?]</ref> that is specific for their environment.
+All plants need essential [[plant nutrition|plant nutrients]] to grow, so it is important to make sure there is a sufficient amount in the potting soil.<ref>{{cite web |last1=Leichty |first1=Corey |title=Does Potting Soil Need Fertilizer? |url=https://donotdisturbgardening.com/does-potting-soil-need-fertilizer/ |website=Do Not Disturb Gardening}}</ref> Some nutrients may be already present in the bulking ingredients.<ref name=uvm>{{cite web |title=pottingmix |url=https://www.uvm.edu/vtvegandberry/factsheets/pottingmix.html |website=www.uvm.edu}}</ref> Peat contains 1% nitrogen that is almost never released. Limestone (for raising [[pH]]) contains mostly calcium ([[calcite]]), but can also contain magnesium ([[dolomitic]]). The latter is preferred as it supplies both elements. A typical proportion of limestone to peat is {{convert|8.5|lb/cuyd|kg/m3}}.<ref name="uvm" /> Coir contains a high amount of electrolytes (salts). In fact, untreated coir contains too much sodium and potassium for plant growth, so it is washed and then buffered (partially replacing salts with other minerals, usually calcium and magnesium) to produce the growth medium. Vermiculite contains some calcium and magnesium, but more importantly it helps retain water and nutrients in the porous structure.
+Nutrients not supplied by the bulk will need to be supplied by the fertilizer. In conventional mixes they may be slow-release formulae of synthetic fertilizers, while organic mixes will use organic source such as [[compost]] (e.g. leaf mold, [[Bark (botany)|bark]] compost or recycled mushroom compost). Overuse of fertilizers will, as with in normal soils, risk damaging the plant.<ref name=uvm/> For compost, the maximum recommended amount is 1 part compost to 1 part bulking material.<ref name=grank/>
-For example, an [[African violet]] would grow better in potting soil containing extra peat moss.
+A [[soil test]] may be done to analyze the chemistry of a potting mix, despite the mix not necessarily being made of soil. As an approximation for indoor home planting, the mix is generally treated as [[greenhouse]] growth medium. The main method is a saturated media extract (SME), which tests the chemical contents of a water extract of the mix.<ref name=uvm/><ref>{{cite web |title=Methods of Greenhouse Media Testing and How They Differ |url=https://ag.umass.edu/greenhouse-floriculture/fact-sheets/methods-of-greenhouse-media-testing-how-they-differ |website=Center for Agriculture, Food, and the Environment |language=en |date=6 March 2015}}</ref>
-Cacti and succulents require sharp drainage, thus requiring a much larger percentage of perlite or sand.<ref>Burne, Geoffrey. "Encyclopedia of Container Gardening." Page 22. Fog City Press. {{ISBN|978-1-877019-43-2}}</ref><!--Best mix for succulents I think is 50% peat moss or coconut coir and 50% sand with grain size 1 to 3 mm, cacti can be grown on 100% perlite or grit I believe -->
+{|class=wikitable
-Insectivorous  plants, such as the [[Venus flytrap]] and the [[pitcher plant]], prefer nutrient-poor <!--acidic ?--> soils common to bogs and fens,<ref>{{cite web|url=http://www.philadelphiaweekly.com/articles/17273/a-e--dirty-buttons|title=Dirty Buttons - Arts and Culture - Philly Weekly|work=philadelphiaweekly.com|url-status=dead|archive-url=https://archive.today/20120907025516/http://www.philadelphiaweekly.com/articles/17273/a-e--dirty-buttons|archive-date=2012-09-07}}</ref> while water-based plants thrive in a heavier topsoil mix.<ref>{{cite web|url=http://features.csmonitor.com/gardening/2008/06/18/creating-a-water-garden-in-a-tub/|title=Creating a water garden in a tub |work=The Christian Science Monitor}}</ref>
+|+Reference levels for potting mix by the SME method<ref name=uvm/>{{efn|UVM data from the 1980s. An extended and updated (~1995) version of this table may be found from UConn.<ref>{{cite web |author1=Dawn Pettinelli, Extension Educator and Dr. Richard McAvoy |title=Interpretation of SME Results for Greenhouse Media |url=https://soiltest.uconn.edu/factsheets/InterpSMEGreenMedia.pdf |publisher=Soil Nutrient Analysis Laboratory, University of Connecticut}}</ref> Significant variation in reference ranges is possible due to procedural differences, so it is recommended to use the test provider's values.}}
+|-
+!Analysis !! Acceptable, min !! Optimum, min !! Optimum, max !! Acceptable, max
+|-
+!scope=row|[[Salinometer|Soluble salt]], [[Conductivity (electrolytic)|mS/cm]]{{efn|May be also written mmhos/cm using the "mho" synonym of S (siemens).}}
+|0.75 || 2.0 || 3.5 || 5.0
+|-
+!scope=row|Nitrate-N, [[parts per million|ppm]]{{efn|Generally written mg/L in newer sources.}}
+|40 || 100 || 200 || 299
+|-
+!scope=row|Phosphorus, ppm
+|3 || 6 || 9 || 18
+|-
+!scope=row|Calcium, ppm
+|80 || 200 || {{N/A}} || {{N/A}}
+|-
+!scope=row|Magnesium, ppm
+|30 || 70 || {{N/A}} || {{N/A}}
+|}
+==Different mixes for different uses==
+The growth medium should be adapted to each plant's (and growth stage's) preference for aeration, drainage, nutrition, and pH.<ref name=grank>[https://gardenranker.com/what-is-potting-soil/ What is Potting Soil?]</ref>
+For seed starting, a "germination mix" is typically light-weight and suitable for starting small-seeded plants. A "seed starting" mix is suitable for larger seeded crops.<ref>{{Cite web|title=Guidelines for Starting Seeds Indoors, from Johnny's Research Team|url=https://www.johnnyseeds.com/growers-library/tools-supplies/seed-starting-transplanting-guidelines.html|access-date=2021-01-19|website=www.johnnyseeds.com}}</ref>  Following early growth, most plants prefer a potting mix that is more well-draining.
+Cacti and succulents require sharp drainage, thus requiring a much larger percentage of perlite or sand.<ref>Burne, Geoffrey. "Encyclopedia of Container Gardening." Page 22. Fog City Press. {{ISBN|978-1-877019-43-2}}</ref> [[Carnivorous plant]]s, such as the [[Venus flytrap]] and the pitcher plant, prefer the nutrient-poor, acidic soils common to bogs and fens,<ref>{{cite web|url=http://www.philadelphiaweekly.com/articles/17273/a-e--dirty-buttons|title=Dirty Buttons - Arts and Culture - Philly Weekly|work=philadelphiaweekly.com|url-status=dead|archive-url=https://archive.today/20120907025516/http://www.philadelphiaweekly.com/articles/17273/a-e--dirty-buttons|archive-date=2012-09-07}}</ref> while water-based plants thrive in a heavier topsoil mix.<ref>{{cite journal|url=http://features.csmonitor.com/gardening/2008/06/18/creating-a-water-garden-in-a-tub/|title=Creating a water garden in a tub |journal=The Christian Science Monitor}}</ref>
 ==Sterilization==
+Commercially available potting soil is sterilized, in order to avoid the spread of weeds and plant-borne diseases.<ref>{{cite web|url=http://www.tcpalm.com/lifestyle/columnists/carol-cloud-bailey-heat-potting-soil-to-prepare-it-for-replanting-ep-402745832-338716581.html|title=Carol Cloud Bailey: Heat potting soil to prepare it for replanting|author=Carol Cloud Bailey|work=TCP|archive-url=https://web.archive.org/web/20160530121331/http://www.tcpalm.com/lifestyle/columnists/carol-cloud-bailey-heat-potting-soil-to-prepare-it-for-replanting-ep-402745832-338716581.html|archive-date=2016-05-30|access-date=2016-05-30|url-status=live}}</ref>
 As with garden soil, potting soil can attract insects. For example, the [[fungus gnat]] is often found around houseplants because it lays eggs in moist potting soil.<ref>{{cite web|url=http://www.azcentral.com/arizonarepublic/home/articles/0628martha0628.html|title=How to minimize dents in carpet from furniture|publisher=azcentral.com}}</ref>
-Commercially available potting soil is sterilized, in order to avoid the spread of weeds and plant-borne diseases. It is possible to reuse commercial potting soil, provided that the remnants of plant roots, fungus, weeds and insects are removed from the mixture through heating before new planting can take place.<ref>{{cite web|url=http://www.tcpalm.com/lifestyle/columnists/carol-cloud-bailey-heat-potting-soil-to-prepare-it-for-replanting-ep-402745832-338716581.html|title=Carol Cloud Bailey: Heat potting soil to prepare it for replanting|author=Carol Cloud Bailey|work=TCP|archive-url=https://web.archive.org/web/20160530121331/http://www.tcpalm.com/lifestyle/columnists/carol-cloud-bailey-heat-potting-soil-to-prepare-it-for-replanting-ep-402745832-338716581.html|archive-date=2016-05-30|access-date=2016-05-30|url-status=live}}</ref> Packaged potting soil is sold in bags ranging from {{convert|5|to(-)|50|lb}}.<ref>Reader's Digest Association. "Care-free Plants". Page 298. ''[[Readers Digest]]. {{ISBN|0-7621-0358-2}}.</ref>
 Infections of [[Legionnaires' disease]] due to potting mix have been reported in [[Australia]],<ref>{{cite journal|vauthors=Speers DJ, Tribe AE |title= Legionella longbeachae pneumonia associated with potting mix|journal=Med. J. Aust.|volume=161|issue=8|pages=509|date=October 1994|doi= 10.5694/j.1326-5377.1994.tb127576.x|pmid=7935133|s2cid= 28552691}}</ref> [[New Zealand]],<ref>{{cite journal|vauthors=Kingston M, Padwell A |title=Fatal legionellosis from gardening|journal=N. Z. Med. J.|volume=107|issue=974|pages=111|date=March 1994|pmid=8127508}}</ref> the [[Netherlands]],<ref>{{cite journal|last1=den Boer |first1=JW |last2=Yzerman |first2=EP |last3=Jansen |first3=R |last4=Bruin |first4=JP |last5=Verhoef |first5=LP |last6=Neve |first6=G |last7=van der Zwaluw |first7=K|title=Legionnaires' disease and gardening|journal=Clin. Microbiol. Infect.|volume=13|issue=1|pages=88–91|date=January 2007|pmid=17184293|doi=10.1111/j.1469-0691.2006.01562.x|doi-access=free }}</ref> the [[United States]],<ref>{{cite journal|title=Legionnaires' disease associated with potting soil--California, Oregon, and Washington, May-June 2000|journal=Can. Commun. Dis. Rep.|volume=26|issue=22|pages=189–92|date=November 2000|pmid=11131692}}</ref> and Japan.<ref>{{cite web|url=https://www.cdc.gov/mmwr/preview/mmwrhtml/mm4934a1.htm|title=Legionnaires' Disease Associated with Potting Soil --- California, Oregon, and Washington, May--June 2000|publisher=[[Centers for Disease Control and Prevention]]}}</ref>
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-== Standardization of the products ==
-{{Expand|date=June 2009}} -->
 == See also ==
@@ Line 58: / Line 81: @@
 == References ==
-{{reflist|2}}
+{{notelist}}
+{{Reflist}}
 {{Plant nutrition}}
+{{Authority control}}
 [[Category:Soil improvers]]

v t e Plant nutrition / Fertilizer
Imbalances	Boron deficiency Calcium deficiency Iron deficiency Magnesium deficiency#Plants Manganese deficiency Molybdenum deficiency Nitrogen deficiency Phosphorus deficiency Potassium deficiency Zinc deficiency Micronutrient deficiency Chlorosis Fertilizer burn
Assimilation	Nitrogen assimilation Phosphorus assimilation Sulfur assimilation Microbial assistance Photorespiration
Methods	Fertigation Fertilizer tree Green manure Hoagland solution Hydroponic dosers Living mulch Nutrient budgeting Nutrient management Organic fertilizer Plant tissue test
Miscellaneous	Soil fertility Nutrient pollution Soil pH Agrobiology
Related concepts	Algal nutrient solutions Biostimulant