BogTrapsA field guide to growing carnivorous plants

Tool

Soil mix calculator for carnivorous plants

Carnivorous plants need nutrient-poor mixes with no fertilizer, and each genus has its preferences. Pick a recipe from the International Carnivorous Plant Society's growing guides, enter your pot, and get the amount of each ingredient [1].

Published October 15, 2026Awaiting editor reviewRuns in your browser; nothing you enter is sent anywhere.

Pot

The recipes

Parts are by volume. The ICPS mix page explains that "one-to-one" means a mix that looks equal once it is mixed; fluffy peat can take three scoops to one of sand to get there [1].

PlantsMixPartsNotes
Venus flytrapSphagnum peat (no fertilizer added) + Coarse silica sand (about 1.5–2 mm, washed)[2]1 : 1The ICPS guide says flytraps also grow in pure peat or pure sphagnum moss, but advises against perlite and other potentially salty components, and against pure peat or moss in short pots.
SarraceniaSphagnum peat (no fertilizer added) + Coarse silica sand (about 1.5–2 mm, washed)[3]1 : 1
Sarracenia (outdoors, well watered)Sphagnum peat (no fertilizer added) + Perlite (washed)[3]1 : 1ICPS: perlite can replace sand for plants outdoors that get plenty of water to flush the soil.
Sarracenia psittacinaSphagnum peat (no fertilizer added)[3]1ICPS: S. psittacina likes pure peat and short pots.
Darlingtonia (seedling pots)Washed sphagnum peat + Coarse silica sand (about 1.5–2 mm, washed)[4]3 : 2The ICPS guide gives 60% washed peat and 40% coarse sand-blasting sand for seedling pots that the plants stay in for two to four years.
CephalotusPeat or chopped long-fiber sphagnum + Coarse silica sand (about 1.5–2 mm, washed)[5]1 : 4ICPS: with the pot sitting in about 1 cm of water and water flushed through occasionally to remove salts.
Subtropical sundews (e.g. D. capensis)Sphagnum peat (no fertilizer added) + Coarse silica sand (about 1.5–2 mm, washed)[6]1 : 1ICPS: anything from 30% to 100% peat works, as does pure sphagnum moss.
Cold temperate sundews (e.g. D. rotundifolia)Sphagnum peat (no fertilizer added) + Coarse silica sand (about 1.5–2 mm, washed)[7]1 : 1
Drosera binataSphagnum peat (no fertilizer added) + Coarse silica sand (about 1.5–2 mm, washed)[8]1 : 2ICPS: the 1:1 CP mix works; 1:2 peat:sand in the top half of the pot is better.
Drosera regiaSphagnum peat (no fertilizer added) + Sand or perlite[9]1 : 1ICPS: also loosely packed long-fiber sphagnum; large, tall pots.
Pygmy sundewsSphagnum peat (no fertilizer added) + Coarse silica sand (about 1.5–2 mm, washed)[10]1 : 2ICPS: at least this much sand in the top 3 cm.
Mexican butterworts (house plants)Sphagnum peat (no fertilizer added) + Coarse sand + Perlite (washed)[11]1 : 1 : 1ICPS: a heavier, water-absorbent mix for plants in a typical house; lighter mixes suit humid greenhouses.
Warm temperate butterwortsSphagnum peat (no fertilizer added) + Silica sand + Perlite (washed)[12]3 : 1 : 1
Cold temperate butterwortsSphagnum peat (no fertilizer added) + Silica sand + Perlite (washed) + Vermiculite[13]2 : 1 : 1 : 1
HeliamphoraLong-fiber Sphagnum moss + Perlite (washed) + Aquatic planting medium (aquatic plant soil)[14]1 : 1 : 1The mix the ICPS guide describes as the current consensus among North American growers.
Nepenthes (cuttings and young plants)Long-fiber Sphagnum moss + Perlite (washed)[15]1 : 1ICPS also lists pure long-fiber sphagnum or 50:50 coir and perlite (coir leached of salts).
Terrestrial bladderwortsSphagnum peat (no fertilizer added) + Coarse silica sand (about 1.5–2 mm, washed)[16]1 : 1ICPS: pure sphagnum moss also works.

How the volume is worked out

The calculator treats a round pot as a cylinder when only the top diameter is given, and as a truncated cone when you add the bottom diameter, which is closer to the shape of most nursery pots. Square pots are handled the same way with side lengths, and trays as simple boxes. Enter the depth of soil you want, not the full height of the pot. The result is the volume of finished mix, which is then divided by the recipe’s parts.

Where the recipes come from

Every recipe is taken from an ICPS page, and the table above names the page for each. The default “CP mix” is equal parts sphagnum peat and coarse sand; the ICPS asks for Canadian (or, in Europe, German) sphagnum peat with no fertilizer, and sharp silica or quartz sand with grains of about 1.5 to 2 mm [1]. The same page says not to use play sand, plaster sand or builder’s sand as they come, and that pool filter sand is too fine [1].

Several genera do better with something else. Cephalotus is grown in a very sandy mix of about 20% peat or chopped sphagnum to 80% sand [5]. The Mexican butterworts kept as house plants do well in equal parts peat, coarse sand and perlite [11]. Heliamphora growers in North America favour equal parts long-fiber sphagnum, perlite and aquatic planting medium [14]. Flytraps grow in pure peat, pure sphagnum or the 1:1 mix, but the ICPS guide warns against perlite and other potentially salty materials for them [2].

Measuring by volume

The ICPS describes its ratios as how the mix looks when finished: depending on how fluffed the peat is, a mix that looks one-to-one may take three scoops of peat to one of sand [1]. Treat the litres as a target and adjust by eye. Keep peat, sand and perlite damp while measuring; it is easier and avoids breathing perlite dust, which the ICPS page warns about [1]. Because some perlite is salty, the page’s author washes it and uses only the pieces that float [1].

For when and how to repot, see the repotting guide; the soil guide explains why ordinary potting compost kills these plants.

Related guides

Other tools

Sources

  1. Peat, Sand, Perlite. International Carnivorous Plant Society. Equal peat and coarse sand as the default mix; sand grain 1.5 to 2 mm; perlite caveats. Accessed October 12, 2026.
  2. Growing Dionaea muscipula. International Carnivorous Plant Society. TDS under 90 ppm; dormancy only for plants facing freezing weather outdoors; LED wattage and lux; USDA-zone advice; soil choices. Accessed October 12, 2026.
  3. Growing Sarracenia. International Carnivorous Plant Society. Hardiness by USDA zone; winter storage; 1:1 peat:sand mix; perlite outdoors; S. psittacina in pure peat. Accessed October 12, 2026.
  4. Growing Darlingtonia californica. International Carnivorous Plant Society. Cool roots below 27 °C; frozen solid only when fully dormant; 60% peat : 40% sand. Accessed October 12, 2026.
  5. Growing Cephalotus follicularis. International Carnivorous Plant Society. About 20% peat or chopped sphagnum to 80% sand. Accessed October 12, 2026.
  6. Growing subtropical Drosera. International Carnivorous Plant Society. No dormancy needed; 10 to 35 °C; mixes from 30% to 100% peat. Accessed October 12, 2026.
  7. Growing cold temperate Drosera. International Carnivorous Plant Society. Hibernacula and a definite winter; 50:50 peat:sand. Accessed October 12, 2026.
  8. Growing Drosera binata. International Carnivorous Plant Society. All forms go dormant; protect from freezing soil; 1:1 or 1:2 peat:sand. Accessed October 12, 2026.
  9. Growing Drosera regia. International Carnivorous Plant Society. Loose winter hibernacula; protection in zone 8 and colder; peat with 50% sand or perlite. Accessed October 12, 2026.
  10. Growing pygmy Drosera. International Carnivorous Plant Society. One part peat to two parts sand. Accessed October 12, 2026.
  11. Growing Mexican Pinguicula. International Carnivorous Plant Society. Succulent winter leaves; cooler and drier in winter; equal peat, coarse sand and perlite. Accessed October 12, 2026.
  12. Growing warm temperate Pinguicula. International Carnivorous Plant Society. Protect from freezing weather; 3 peat : 1 sand : 1 perlite. Accessed October 12, 2026.
  13. Growing cold temperate Pinguicula. International Carnivorous Plant Society. Winter buds in autumn; need cold winters; 2 peat : 1 sand : 1 perlite : 1 vermiculite. Accessed October 12, 2026.
  14. Growing Heliamphora. International Carnivorous Plant Society. Tepui temperatures 7 to 23 °C; equal sphagnum, perlite and aquatic planting medium. Accessed October 12, 2026.
  15. Nepenthes Propagation via stem cuttings. International Carnivorous Plant Society. Long-fiber sphagnum, or 50:50 sphagnum:perlite, or 50:50 coir:perlite. Accessed October 12, 2026.
  16. Growing Genlisea and terrestrial Utricularia. International Carnivorous Plant Society. Pure sphagnum or the 1:1 peat:sand mix. Accessed October 12, 2026.