Best Potting Soil (2026): Picks for Pots, Houseplants and Cacti

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The best potting soil for most outdoor pots and planters is Miracle-Gro Potting Mix, a peat-based container mix with plant food in the bag, linked here in the 16 quart size. It finished first of 14 bagged mixes in Epic Gardening's pepper trial, and Fine Gardening's five-mix tomato test called it "probably the best all-around mix" of the group. For organic gardening, the pick is Espoma Organic Potting Mix, which Espoma makes with no synthetic plant food. For raised planters and big pots, Black Gold Natural & Organic Potting Mix comes in a 2 cubic foot bag.

The other three picks cover houseplants, a mix with no peat moss, and cacti and succulents. Below the picks, one table sets out what three side by side tests found, a second puts the labels side by side, and a third works out how much mix a pot takes from the makers' own fill figures. The advice on soil types, houseplants, fungus gnats, peat, drainage and reusing old mix comes from university extension services, each named where it appears.

Jump to: Test results | Labels table | How much a pot takes | Potting mix vs garden and raised bed soil | Houseplants and cacti | Fungus gnats | Peat or peat-free | Drainage | Reusing old mix

Start here: which potting soil for your pots

• Outdoor pots of flowers, vegetables and herbs: Miracle-Gro Potting Mix (pick 1).
• Organic gardening, indoors or out: Espoma Organic Potting Mix (pick 2).
• Raised planters, half barrels and other big containers: Black Gold Natural & Organic Potting Mix in the 2 cubic foot bag (pick 3).
• Houseplants and potted herbs indoors: Miracle-Gro Indoor Potting Mix (pick 4).
• No peat moss, for tropical houseplants: Rosy Soil Houseplant Potting Soil (pick 5).
• Cacti, succulents and jade plants: Hoffman Cactus and Succulent Soil Mix (pick 6).

Not sure how much to buy? Espoma's own chart puts a 12 inch pot at 11 quarts, and Miracle-Gro says one 16 quart bag fills one 12 inch container; see how much mix a pot takes.

The best potting soil, by job

1. Miracle-Gro Potting Mix: best overall

Miracle-Gro's everyday container mix, linked here in the 16 quart bag. By its listing the plant food in it lasts up to 6 months, and Miracle-Gro makes it for every kind of container plant: flowers, vegetables, shrubs, annuals and perennials. In 2014, Fine Gardening's tester listed its ingredients as "forest-products compost, Canadian sphagnum peat moss, perlite, a wetting agent, and fertilizer," and found it fine textured and dark. The listing says one 16 quart bag fills one 12 inch container, though the root ball changes the amount.

Why it is the pick: two separate side by side tests put it on top. Epic Gardening grew the same pepper variety in identical 5 gallon grow bags filled with 14 different bagged potting mixes, watered them all by drip, labeled the bags by number to keep brand names out of the judging, and checked them at three, six and nine weeks. Miracle-Gro Potting Mix finished first: by week nine its pepper plant had the biggest, greenest foliage of the trial and was carrying 10 to 12 peppers. In Fine Gardening's test, Jeff Gillman grew tomatoes in five commonly sold mixes and measured each mix's air and water holding; he rated this one good for air and excellent for water and called it "probably the best all-around mix that we tested."

Good to know: it is not an organic mix. Epic credits its quick-release synthetic fertilizer for part of the fast start and says that feed tapers off, so plan to fertilize if you reuse the mix next season (see reusing old mix). One test went the other way: GreenStalk sowed lettuce, arugula and spinach seeds straight into six mixes in its vertical planters, added no fertilizer to that planter, and ranked Miracle-Gro last; its seeds were the slowest of the six to come up. If you sow greens from seed straight into a planter, weigh that result (GreenStalk's favorite store-bought mix is under Also considered). The listing's directions: fill the pot about a third full, set the plant in, then fill the rest and press lightly.

2. Espoma Organic Potting Mix: best for organic gardening

Espoma's ingredient line starts with "60-70% processed forest products," then "sphagnum peat moss, perlite, humus, limestone to adjust pH," and a feed of "earthworm castings, alfalfa meal, kelp meal, feather meal, & yucca extract." Espoma also adds Myco-tone, its own blend of endo and ecto mycorrhizae. Espoma calls the mix "100% Natural & Organic Approved," and the listing says no synthetic plant foods or chemicals go into it. It is made for indoor and outdoor containers, from houseplants to vegetables and herbs. Espoma sells it in 4, 8 and 16 quart and 1 and 2 cubic foot bags; the link here is the 8 quart bag.

Why it is the pick: Espoma spells out its organic wording and feed on its page, and a test and a reviewer's vote stand behind the mix. In Fine Gardening's 2014 five-mix test the Espoma mix "performed well in the tests," and its tomato plants came out second heaviest of the five at 42.7 grams, against 37.0 for pick 1. Fine Gardening printed that bag's ingredients as "sphagnum peat moss, peat humus, perlite, dolomitic limestone, and mycorrhizae," with no forest products, so the bag it tested was an earlier recipe than today's. The Spruce names Espoma Organic Potting Mix its best soil for indoor plants, saying in its summary that the mix is organic and holds moisture well.

Good to know: Fine Gardening rated that earlier recipe's water holding moderate, the lowest of the five mixes, and one of its tomatoes developed blossom-end rot, with low calcium and fairly low nitrogen on a nutrient test, so keep up with watering and feeding through a hot summer. Gillman also doubted the value of the added mycorrhizae, noting that plants that are well fed seldom need extra. Espoma's directions say to let the soil dry to the touch between waterings and warn that outdoor pots can need water once a day in hot, dry weather. On October 26, 2026 this bag was sold by a third-party seller.

3. Black Gold Natural & Organic Potting Mix, 2 cubic feet: best for raised planters and big pots

Sun Gro, the maker, calls Black Gold Natural & Organic Potting Mix "an all-purpose mix designed for containers and raised beds" and says it is OMRI Listed. Sun Gro lists Canadian sphagnum peat moss, bark, compost, perlite and pumice or cinders, with earthworm castings, an organic fertilizer, an organic wetting agent and calcium silicate. Sun Gro sells it in 8 and 16 quart and 1, 1.5 and 2.0 cubic foot bags. The link here is the 2 cubic foot bag, which Amazon lists as "Black Gold Natural and Organic Soil" and describes as a natural and organic potting soil with fertilizer added, with perlite and pumice blended in for air.

Why it is the pick: volume. Two cubic feet is about 51.4 dry quarts, more than three times the 16 quart bag of pick 1, which is what an elevated planter or a big patio pot needs (see how much mix a pot takes). Sun Gro lists raised beds, hanging baskets and window boxes, houseplants, indoor and outdoor containers, and vegetables and herbs among its uses. None of the side by side tests we read included it, so this pick rests on Sun Gro's own page and the listing.

Good to know: the listing notes it is not sold in Oregon. Fill a big pot where it will stand, since Penn State points out that moving a pot means moving the plant, the mix and the water in it too. For a raised bed filled straight onto the ground, a bagged potting mix is not the only choice; see potting mix vs raised bed soil. On October 26, 2026 this bag was sold by a third-party seller.

4. Miracle-Gro Indoor Potting Mix: best for houseplants

Miracle-Gro's houseplant mix, sold in full as "Miracle-Gro Indoor Potting Mix for All Plants" and linked here in the 16 quart bag. The listing describes a blend of peat moss, coconut coir and perlite with plant food that lasts up to 6 months, made for herbs and for climbing, foliage and flowering plants. Miracle-Gro's product page gives the feed as 0.25-0.13-0.19 and says the mix leaves out compost and bark, which it says are known to shelter fungus gnats. Miracle-Gro renamed it from Indoor Potting Mix and says the mix inside did not change.

Why it is the pick: it is made for the conditions houseplants live in. Penn State Extension advises a soilless potting mix made for potted plants, of perlite, vermiculite, peat moss or coir with added fertilizer, and warns that garden soil in indoor pots can bring disease and pests; this is that kind of mix, with the feed already in it. By the listing and Miracle-Gro's page, the 16 quart bag fills four 8 inch pots, and Amazon's listing for Miracle-Gro's 6 quart bag of the same mix says it fills four 6 inch pots.

Good to know: Miracle-Gro says to water whenever the top inch of the mix feels dry, never to let the pot stand in water, to start feeding with an indoor plant food 30 days after planting, and to repot each year in fresh mix. It recommends gardening gloves while you handle it and washing your hands afterward. For Miracle-Gro's gnat note and the extension advice on watering, see fungus gnats.

5. Rosy Soil Houseplant Potting Soil: best peat-free mix

Rosy Soil's houseplant mix leaves peat moss out entirely. By its listing, biochar, bark fines, compost, worm castings and mycorrhizae take the place of peat, with sand and biochar to keep it open, and no synthetic fertilizers. Rosy Soil's own page lists biochar, pine bark fines, mycorrhizae, worm castings, compost and diatomaceous earth, and calls the mix OMRI Listed and peat-free. It is linked here in the 4 quart bag, which the listing says fills 2 to 3 medium pots.

Why it is the pick: it is the pick for growers who would rather leave peat alone. The University of Illinois Extension says peat builds up at about a millimeter a year while harvest takes 22 centimeters a year, and names composted wood fiber and biochar among the peat alternatives that research shows promise for. Rosy Soil makes the mix for tropical houseplants such as monstera, pothos, philodendron and ferns, and for herbs. None of the side by side tests we read included it, so this pick rests on Rosy Soil's page and the listing.

Good to know: compost and bark are the two ingredients Miracle-Gro leaves out of its indoor mix because of fungus gnats; Rosy Soil says the diatomaceous earth in its mix "helps protect plants from soil-dwelling gnats." Either way, let the top of the mix dry between waterings (see fungus gnats). Rosy Soil also sells the mix in 8, 16 and 32 quart bags. On October 26, 2026 it was sold on Amazon by Rosy Soil itself.

6. Hoffman Cactus and Succulent Soil Mix: best for cacti and succulents

Sold as "Hoffman Organic Cactus and Succulent Soil Mix": a ready to use mix that Hoffman formulates for both jungle and desert cacti, linked here in the 4 quart bag. The listing calls it pH balanced and says it gives the drainage cacti need. In a side by side of four bagged cactus mixes, the writer at Succulent Plant Care listed its ingredients as compost, peat moss, sand and limestone.

Why it is the pick: it is a ready to use mix made for these plants, with the sand that extension recipes call for. The University of Maryland Extension says a bought mix for cacti and succulents needs less humus and a high share of sand, and the University of Minnesota Extension suggests one part potting soil to one part coarse sand. Hoffman's mix includes sand, by Succulent Plant Care's ingredient list, though no source we found says how much, and it is one of the four mixes Succulent Plant Care compared side by side, and the writer then used it for a few months.

Good to know: Succulent Plant Care found it stays wet and adds about a quarter perlite to make it drain faster, and called it an OK product on its own. Minnesota's test is a good one to run on any cactus mix: wet it, squeeze a handful, and it should fall apart when you open your hand. Use pots with drainage holes and let the mix dry out completely between waterings, as Minnesota advises. Hoffman also sells a 10 quart bag.

How we chose these

We compared the bagged potting mixes in Amazon's catalog by what their makers say is in the bag: the base (peat moss, forest products, compost or coir), the added feed, any organic listing, the volume you get, and what the maker says the mix is for. For each pick we read the maker's product page, where one turned up, and the Amazon listing; Hoffman publishes no product page that we could find, so for pick 6 we read the listing, two retailer pages and Succulent Plant Care's ingredient list. Then we read the side by side tests: Epic Gardening's 14-mix pepper trial (updated 2024), Fine Gardening's five-mix tomato test (2014), GreenStalk's six-mix test of greens sown from seed and Succulent Plant Care's comparison of four cactus mixes (bought in 2020). Epic and GreenStalk both call their trials informal: Epic says its "backyard experiment is not a valid scientific result," and GreenStalk calls its test neither scientific nor exhaustive. The Spruce's indoor plant soil page would not load for us, so only the summary in its search result is used.

Our floor, for the picks and for the notes under Also considered: in stock on Amazon and sold new, when we checked on October 26, 2026. Each pick met it. Ingredients, feeds, sizes and directions come from the maker pages and listings, named where they appear. Growing advice comes from extension services at Maryland, Penn State, Minnesota, Clemson, Colorado State, Oklahoma State, Iowa State, Illinois, Florida, Wisconsin, California and Louisiana State, and from Washington State University's Linda Chalker-Scott, each named where it appears.

Also considered: mixes that missed the list and why

FoxFarm Ocean Forest Potting Soil. FoxFarm's most popular mix, by its own page: sphagnum peat moss, sandy loam and aged forest products, fed with crab meal, fish emulsion, bat guano and earthworm castings, and ready to use from the bag. In Epic Gardening's pepper trial it finished sixth of 14, five places behind pick 1, though Epic found its plants large, branched and bushy and describes it as made with OMRI-approved ingredients. It met our floor on October 26, 2026, sold by a third-party seller.

FoxFarm Happy Frog Potting Soil. GreenStalk's favorite bag mix: in its test of greens sown from seed it ranked second, behind GreenStalk's own blend of old potting soil and amendments, with steady growth every week. The other two tests disagree: Epic placed it seventh of 14 and says plants in it may need extra feeding by midsummer, and in Fine Gardening's test it was the coarsest mix and grew the smallest tomatoes, 24.7 grams. It met our floor on October 26, 2026.

Miracle-Gro Moisture Control Potting Mix. Made for pots that dry out: the listing says it absorbs "up to 33% more water" than a basic potting soil made without its peat moss, coir and wetting agent. Epic placed it fourth of 14 and found it stayed evenly moist and drained well. Fine Gardening's 2014 test measured it holding no more water than the other mixes and drying down no slower, though its tomatoes were the heaviest of the five at 51.3 grams, and they developed blossom-end rot. Pick 1 finished higher in Epic's trial. It met our floor on October 26, 2026.

Miracle-Gro Organic Container Mix. The top organic mix in Epic Gardening's pepper trial: it finished third of 14, behind two mixes with quick-release synthetic feed, and Epic recommends it for organic growers. We found no Amazon listing under that name and could not tie the Miracle-Gro organic mixes sold on Amazon under other names to the bag Epic tested, so it is not linked. Fine Gardening and GreenStalk did not test it.

Burpee Premium Organic Potting Mix. A coconut coir mix with plant food that Burpee says feeds for up to 3 months and is OMRI labeled for organic use, for raised beds or patio containers. It met our floor on October 26, 2026, but none of the tests we read covered it, and pick 2 has The Spruce's vote and Fine Gardening's 2014 test of an earlier recipe behind it.

Back to the Roots indoor mix. Another peat-free houseplant mix, sold as "Back to the Roots 100% Organic Indoor Potting Mix": its listing calls it organic and peat-free and says it is made without bark or compost. It met our floor on October 26, 2026. None of the tests covered it either, and pick 5's maker lists every ingredient on its own page.

Espoma Organic Cactus Mix. By its listing, sphagnum peat moss, humus and perlite with Myco-tone, for cacti, succulents, palms and citrus. It met our floor on October 26, 2026, but its listing names no sand, and none of the tests we read covered it.

PRO-MIX potting mixes. GreenStalk ranked PRO-MIX with worm castings fourth of six and said the mix can be hard to rewet once it dries out; Epic placed PRO-MIX Premium Organic eighth of 14. We could not tie any PRO-MIX potting mix listing we found on Amazon to the bags the two tests used, so none is linked.

Coast of Maine Bar Harbor Blend. An organic potting soil with perlite for containers and baskets, by its listing. Its 2 cubic foot bag met our floor on October 26, 2026, but none of the tests covered it.

What three side by side potting soil tests found

Three publishers grew the same plants in different bagged mixes side by side and wrote up the results. They tested different crops in different ways, which helps explain why they disagree. Epic Gardening transplanted pepper seedlings into 5 gallon grow bags and judged growth, color, flowers and fruit over nine weeks. Fine Gardening, in a 2014 magazine test, grew tomatoes in five mixes, measured each mix's air and water holding with standard nursery methods, and weighed the plants at the end. GreenStalk sowed lettuce, arugula and spinach seeds straight into its vertical planters and added no fertilizer, apart from one feeding for one slow mix.

What it shows: for plants you transplant into a pot, the fed Miracle-Gro mix came first in Epic's trial and was Fine Gardening's best overall, though two mixes there grew heavier tomatoes, and Epic's testers credit its quick-release feed for the fast start. For seeds sown straight into a planter with no extra feeding, GreenStalk's result points the other way, toward Happy Frog, which Fine Gardening found the coarsest of its five. Epic adds that a longer trial might favor the organic blends, because their feed releases over a longer time. None of the three tested Black Gold or any houseplant, peat-free or cactus mix, which is why picks 3 to 6 rest on makers' pages, listings and extension advice, plus one grower's comparison for pick 6.

What is in each bag? The labels side by side

Two things stand out. Five of the six contain peat moss, and only pick 5 leaves it out entirely. And "organic" means different things on different bags: Sun Gro and Rosy Soil say their mixes are OMRI Listed, Espoma uses its own "Natural & Organic Approved" wording, and Hoffman puts the word in the product name. The University of Maryland Extension explains what usually changes in an organic mix: makers leave out the chemical wetting agents and use organic fertilizers in place of synthetic ones.

How much potting soil does a pot take?

Buy by the pot, not the bag. Two of the makers publish fill figures, and they do not agree: Espoma's chart puts a 12 inch pot at 11 dry quarts, while Miracle-Gro says one 16 quart bag of pick 1 fills one 12 inch container. Both say the real amount depends on the root ball. The table sets the makers' figures beside our own arithmetic for a straight-sided pot as deep as it is wide. Real pots taper toward the base, and you leave an inch or so at the rim for water, so most take less than that.

Our arithmetic: the volume of a cylinder, divided by 67.2 cubic inches to a dry quart, the unit potting mix bags are sold in. The same conversion gives 25.7 dry quarts to the cubic foot, the figure Espoma prints. Two bigger containers worked the same way:

• A 5 gallon grow bag, the size Epic Gardening used in its trial, holds about 17.2 dry quarts when full: one 16 quart bag of pick 1 and a little more.
• An elevated planter 2 feet by 4 feet with soil 10 inches deep holds about 6.7 cubic feet, or about 171 dry quarts: a little over three 2 cubic foot bags of pick 3, or about eleven 16 quart bags.

Plan on the higher figure when the makers disagree, since a half-empty pot means a second trip. Leftover mix keeps if you seal it: Miracle-Gro's indoor mix page says to close the bag with a clip or tape and store it somewhere cool and dry, out of direct sun.

Potting mix, potting soil, garden soil or raised bed soil?

The names on the bags blur together, so it helps to know what extension services mean by them. Most bagged potting mixes hold no true soil at all. The University of Maryland Extension calls commercial soilless mixes an excellent choice for containers: light, well drained, able to hold water and nutrients, and generally free of weeds, insects and disease, made from ingredients such as peat moss, coir, compost, composted bark, perlite and vermiculite. Maryland's indoor plant page goes further: it suggests avoiding products sold as "potting soil," which it says are usually too dense for good aeration, and adding perlite or vermiculite to any you do buy. Makers use both names for soilless bags: pick 5 is sold as a potting soil, and pick 3's maker calls it a potting mix while its Amazon listing calls it soil. David Hillock of Oklahoma State University Extension puts it plainly: potting soil is not really soil at all but a blend of peat, vermiculite and composted matter. So read the ingredients rather than the name.

Garden soil does not belong in pots. Maryland says garden soil is too dense for good air and water movement in a container and can drown roots, most of all in shallow pots, and that topsoil should go only into very large containers and make up no more than 10 percent of the volume. Penn State warns that garden soil in indoor pots can bring disease and pest problems, and Colorado State says it drains poorly and carries weed seeds and pathogens. Epic Gardening tested only bags labeled potting mix for the same reason: it notes that mixes labeled garden soil are made for in-ground use.

Raised bed soil is a different recipe. A raised bed sits on the ground, and Iowa State University Extension's suggested fill is mostly real soil: equal parts topsoil, organic matter and coarse sand, or about 70 percent topsoil and 30 percent compost, worked into the ground beneath so no layers form. Our guide to building a raised garden bed covers the fill and the mistake that costs the most. A potting mix makes sense where the container stands off the ground: an elevated planter, a window box, a big pot or a half barrel. That is the job pick 3's big bag is for, and Sun Gro lists raised beds among its uses too.

Seed starting mix is finer still. For sowing seeds in cell trays, a fine seed starting mix is the better fit, and our seed starting mix guide compares those bags. Once seedlings move up into real pots, the mixes on this page take over.

Houseplants, cacti and orchids: matching the mix to the plant

The University of Maryland Extension sorts houseplant mixes into four groups, and they map neatly onto the picks:

• Foliage plants want a moderately rich mix that holds moisture and fertility well. Picks 4 and 5 are made for them, and Clemson's Home and Garden Information Center says a high-quality mix usually carries slow-release fertilizer for a few months, and Miracle-Gro says the feed in its indoor mix lasts up to 6 months.
• Flowering houseplants such as African violets, gloxinias and begonias often have their own bag, sold as African violet mix; Maryland says it should be about half humus-rich material without staying soggy after watering.
• Cacti and succulents need less humus and a high share of sand: a cactus mix such as pick 6, with perlite added if it stays wet, or Minnesota's one part potting soil to one part coarse sand.
• Orchids and other epiphytes such as bromeliads and anthuriums grow on tree branches in nature, and Maryland says their roots may rot in regular potting mix. They need a coarse, lumpy mix that dries quickly, such as one of peat moss, fir bark and charcoal. None of the picks is an orchid mix.

Penn State adds two practical points for indoor pots. Unglazed clay pulls water and salts out of the mix, so plants in clay need watering more often than plants in plastic, which makes terracotta a good match for succulents and plastic better for plants that like to stay moist. And moisten the potting mix before you repot, so it takes up water evenly; Maryland's container page says the same of soilless mixes, which tend to shed water when they are dry. For the pot itself, Colorado State suggests a pot only one or two inches wider than the old one.

Fungus gnats: what the mix can and cannot do

Fungus gnats are the small dark flies that hover around houseplants. The University of Wisconsin says they are commonly associated with overwatered houseplants, that the adults are a nuisance rather than a threat to the plant, and that the larvae feed mostly on fungi and decaying organic matter in the soil, though large numbers can damage roots. The University of California's integrated pest management program adds that damage is worst in seedlings and young plants in moist, organically rich soil.

Some makers design their indoor mixes around the problem. Miracle-Gro leaves compost and bark out of pick 4 because, it says, they are known to shelter fungus gnats; Back to the Roots' listing says the same of its indoor mix; and Rosy Soil adds diatomaceous earth to pick 5, which it says "helps protect plants from soil-dwelling gnats." Whatever the mix, the extension services put the weight on watering:

• Let the top of the mix dry out. Wisconsin says to let the top inch dry before you water, or to water from below so the surface stays dry, and Colorado State says to let the top 1 to 2 inches dry between waterings, since dry mix kills eggs and larvae and puts egg-laying females off.
• Use clean, finished mix. California advises buying only pasteurized potting mix, storing it closed and off the ground, and keeping organic matter that is not fully composted out of a potting mix.
• Repot when the mix breaks down. Colorado State recommends repotting every so often, especially once the old mix has broken down and holds too much water.

Peat moss or peat-free?

Peat moss is in most bagged mixes because it works: the Hennepin County Master Gardeners in Minnesota call it a good, lightweight amendment that improves drainage, water holding and air flow. The case against it is where it comes from. The University of Illinois Extension says peat builds up in wetlands at about a millimeter a year while the industry harvests 22 centimeters a year, and that a harvested peat wetland can take up to 20 years to recover its functions once reclaimed. The Hennepin County Master Gardeners add that most peat used in the United States comes from Canada.

The usual stand-ins each have a catch:

• Coconut coir holds water and nutrients much like peat, Illinois says, but it can carry salt from processing. Clemson says to rinse it well before use, and the University of Florida notes that coir may need more nitrogen and less potassium than peat.
• Compost adds nutrients, and the University of Maryland Extension says vegetables, herbs and flowers can grow in 100 percent compost, though they will still need fertilizer as the season goes on.
• Composted wood fiber and biochar are newer; Illinois says research on them as potting mix ingredients shows promise. Pick 5 is built on biochar and bark.

To make your own peat-free mix for vegetables, Illinois suggests "two parts compost, two parts coconut coir, and one-part sharp builder's sand or perlite."

Drainage holes, not gravel

Every pot needs a hole in the bottom. Penn State says a container needs drainage holes so excess water can drain away and the mix does not become waterlogged, and suggests drilling one if needed, or using a pot without one only as a decorative holder for a plain pot that has one.

The layer of gravel or broken pots that many guides tell you to put in the bottom does the opposite of what it promises. Linda Chalker-Scott, Washington State University's extension urban horticulturist, explains that water will not move from a fine potting mix into a coarser layer below until the mix above is saturated, so a layer meant to keep the soil from getting waterlogged ends up causing it. Her bottom line: "Planting containers must have drainage holes for root aeration," and drainage material only hinders water movement. The University of Maryland Extension agrees: do not fill the bottom of the pot with gravel. Espoma's own directions still suggest a layer of small stones to keep soil from escaping; if mix washes out through a big hole, Colorado State's fix is a coffee filter, a scrap of porous landscape fabric or a piece of broken pot over the hole instead.

Can you reuse potting soil?

Yes, if the plants in it were healthy. David Hillock, consumer horticulturist at Oklahoma State University Extension, says to go ahead and reuse a mix that grew healthy plants with no disease problems, but to expect two changes: the plants have used up the fertilizer the maker added, which generally lasts three to six months, and the old mix is more compacted than fresh. His fixes:

• Feed it. Add a slow-release fertilizer to the used mix before replanting.
• Freshen it. Maryland suggests mixing last year's mix half and half with fresh mix or compost, and the LSU AgCenter suggests a 1 to 3 ratio of new mix to old. In big containers, Hillock suggests replacing just the top 6 inches or so with fresh mix.
• Do not reuse a sick pot. Hillock and Maryland both say to skip reuse after disease problems; Hillock adds weeds and insects to that list, since pathogens stay in the mix long after the plant is gone.

GreenStalk's own result is an encouraging footnote. The blend that finished at the top of its six-mix test was GreenStalk's own blend of used Happy Frog and PRO-MIX, as much as two years old, refreshed with fertilizers and amendments such as worm castings and kelp meal. Old mix you would rather not reuse can go on the compost pile or into garden beds, as Hillock suggests.

Related guides

To check the pH of a potting mix, our soil test kit guide includes a pH pen made for soil, coir and potting mixes. For homemade compost to blend into containers, our compost bin guide picks bins by job, from kitchen caddies to tumblers. And for watering a shelf of houseplants, our watering can guide includes a long-spout can for indoor plants.

Frequently asked questions

What is the best potting soil?

For most outdoor pots, Miracle-Gro Potting Mix: it finished first of 14 mixes in Epic Gardening's pepper trial and was Fine Gardening's best all-around mix in a five-mix tomato test. For organic gardening, Espoma Organic Potting Mix; for houseplants, Miracle-Gro Indoor Potting Mix; for cacti and succulents, Hoffman Cactus and Succulent Soil Mix.

What is the difference between potting soil and potting mix?

Often very little: makers put both names on bags of soilless mix, and Oklahoma State University Extension notes that potting soil is not really soil at all but a blend of peat, vermiculite and composted matter. The University of Maryland Extension suggests avoiding products sold as potting soil, which it says are usually too dense, and adding perlite or vermiculite to any you do buy, so read the ingredients rather than going by the name.

Can I use garden soil in pots?

No. The University of Maryland Extension says garden soil is too dense for good air and water movement in a container and can drown roots, and Colorado State adds that it carries weed seeds and pathogens. Maryland allows a little topsoil only in very large containers, at no more than 10 percent of the volume.

What is the best potting soil for indoor plants?

For most houseplants, a soilless mix made for indoor pots, such as Miracle-Gro Indoor Potting Mix, which feeds for up to 6 months and leaves out compost and bark. For a peat-free choice, Rosy Soil Houseplant Potting Soil is built on biochar, bark and compost. Cacti and succulents need a sandier mix, and orchids a coarse bark mix.

Can I use potting mix in a raised bed?

Yes, especially in an elevated planter or a bed with no ground beneath it, but it is not the only option. Iowa State University Extension suggests filling a raised bed on the ground with equal parts topsoil, organic matter and coarse sand, or about 70 percent topsoil and 30 percent compost. A big bag of potting mix suits planters that stand off the ground.

Can you reuse potting soil?

Yes, if the plants were healthy. Oklahoma State University Extension says to add a slow-release fertilizer, since a bag's added fertilizer generally lasts three to six months, and to loosen the compacted mix; Maryland suggests mixing it half and half with fresh mix or compost. Do not reuse mix from plants that had disease, weed or insect problems.

Should I put gravel in the bottom of a pot?

No. Washington State University's Linda Chalker-Scott explains that water will not move from potting mix into a coarser layer below until the mix is saturated, so a gravel layer brings on the waterlogging it is meant to prevent. Use a pot with a drainage hole and fill it with potting mix all the way down; a coffee filter over a big hole keeps mix in.

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