Potting mix

Roots in a pot have nowhere else to go, so the mix has to hold water and air at the same time. That is why soil dug from the ground rarely works on its own.

Why not garden soil?

Oregon State Extension advises against garden soil or topsoil in containers: it can be too heavy and hold too much moisture. NC State adds that field soil can bring pests and weed seeds with it, and its vegetable handbook says never to use yard soil in containers. Use a potting mix sold for containers, or make one from the ingredients below.

Source: Oregon State University Extension Service; NC State Extension; NC State Extension, checked 26 October 2026.

What each ingredient does

Coir (cocopeat): Fibre from coconut husks. UF/IFAS Extension notes it is sold as a compressed brick that expands when wetted, may need extra nitrogen and less potassium than peat-based mixes, and can carry salt that should be washed out.
Peat moss: UF/IFAS calls it the most common soilless ingredient because it is cheap and holds a lot of water; it is acidic, so lime is usually added.
Perlite: A sterile, pH-neutral, lightweight volcanic rock that adds air space and drainage (UF/IFAS; NC State).
Vermiculite: Holds water and attracts nutrients (NC State). UF/IFAS warns that rough handling compacts it and removes its air space; it suggests medium grade for seedlings and coarse grade for older plants.
Compost: Holds water and supplies nutrients; UF/IFAS notes its quality depends on what went into it. NC State suggests keeping compost to 15 to 40 percent of a container mix, partly because it often has a high pH.
Sand: Adds weight, which helps top-heavy plants stay upright. Use coarse builder’s sand: UF/IFAS says fine and plaster sands make a dense mix.
Bark: Makes a light, airy mix that holds little water; UF/IFAS says it should be aged before use.

Source: UF/IFAS Extension, University of Florida; NC State Extension, checked 26 October 2026.

Example recipes

UF/IFAS Extension publishes simple recipes by volume (parts). They are written with peat; if you use coir instead, remember UF/IFAS’s notes above about rinsing out salt and adding nitrogen. That substitution is our suggestion, not part of the published recipe.

Foliage plants: 2 parts peat, 1 part perlite, 1 part coarse sand.
Succulents: 2 parts soil, 1 part peat moss, 1 part perlite, 1 part coarse sand.
Seedlings: 2 parts compost, 2 parts peat moss, 1 part pre-wetted vermiculite.

UF/IFAS says garden soil used in a mix like the succulent recipe should first be sterilised to kill disease organisms and weed seeds. Plants with special needs are covered on their own pages: aloe and desert rose want a cactus-type mix, ixora prefers acidic soil, and NC State suggests a soil-based mix for rubber plant.

Source: UF/IFAS Extension, University of Florida; NC State Extension; NC State Extension; NC State Extension; NC State Extension, checked 26 October 2026.

Mix for seeds

NC State says a seed-starting medium should be fine and uniform yet airy and loose, and that garden soil should not be used because it is not sterile, is too heavy and drains poorly. For comparison, TNAU raises tomato seedlings for farms in pro-trays filled with sterilised cocopeat.

Source: NC State Extension; TNAU Agritech Portal, Tamil Nadu Agricultural University, checked 26 October 2026.

Feeding plants in pots

NC State prefers controlled-release, slow-release or liquid fertilisers for containers, for example a liquid feed weekly at half strength or every two weeks at full strength, following the product label. Over-feeding pushes leafy growth at the expense of flowers and fruit. A white crust on the mix is salt build-up: run water slowly through the pot for several minutes to flush it out, and wash old pots before re-using them.

Source: NC State Extension, checked 26 October 2026.

General gardening information, not professional advice. Plant toxicity details are a starting point, not veterinary or medical advice: if a pet or child may have eaten a plant, contact a veterinarian or doctor promptly.