Most carnivorous plants die in ordinary potting compost, and the right mix differs from plant to plant. Pick your plant, enter the size and number of your pots, and the calculator turns each published recipe into amounts you can measure out: litres, US quarts and cups. The recipes come from the growing guides of the International Carnivorous Plant Society (ICPS) and from the nursery Sarracenia Northwest.
How the Calculator Works
Recipes are given in parts by volume, so “1 part peat to 1 part sand” means equal scoops of each. The calculator treats your pot as a straight-sided cylinder, works out its volume, multiplies by the number of pots and splits the total by the parts in each recipe. Most pots narrow towards the base, so the result is a little more than you need. For the Mexican butterwort mix it also adds the dolomitic lime the ICPS guide uses: about 1 tablespoon per cup of mix.
Where the Recipes Come From
| Plant | Recipe (parts by volume) | Source |
|---|---|---|
| Venus flytrap | 1 peat : 1 sand (“CP mix”); pure sphagnum moss; or pure peat in taller pots | ICPS |
| Venus flytrap | 1 peat : 1 perlite | Sarracenia Northwest |
| Sarracenia | 1 peat : 1 sand, or perlite instead of sand outdoors | ICPS |
| Sarracenia | 1 peat : 1 perlite | Sarracenia Northwest |
| Subtropical sundews | CP mix from 30% to 100% peat, or pure sphagnum moss | ICPS |
| Forked sundew (D. binata) | 1 peat : 1 sand; 1 peat : 2 sand in the top half of the pot | ICPS |
| Pygmy sundews | 1 peat : 2 sand | ICPS |
| Cephalotus | 20% peat or chopped sphagnum : 80% sand, pot standing in about 1 cm (0.4 inch) of water | ICPS |
| Mexican butterworts | 1 peat : 1 coarse sand : 1 perlite, plus about 1 tablespoon of dolomitic lime per cup | ICPS |
| Temperate butterworts | 2 peat : 1 silica sand : 1 perlite : 1 vermiculite | ICPS |
| Nepenthes | 1 dried sphagnum moss : 1 perlite | Sarracenia Northwest |
| Heliamphora | 1 long-fibred sphagnum : 1 perlite : 1 aquatic planting medium, and two alternatives | ICPS |
| Darlingtonia | 1 peat : 1 to 2 perlite or pumice : 1 orchid bark, and two alternatives | ICPS |
| Terrestrial bladderworts | Pure sphagnum moss, or 1 peat : 1 sand | ICPS |
Where the Sources Differ
The biggest split is perlite for Venus flytraps. The ICPS guide says to avoid perlite, pumice and other potentially salty ingredients for flytraps, while Sarracenia Northwest grows its flytraps and Sarracenia in equal parts peat and perlite. For Sarracenia, the ICPS allows perlite in place of sand only for plants outdoors that get plenty of water to flush the soil. The calculator shows both recipes so you can choose.
For Cephalotus, the ICPS says growers have no real consensus. The classic 50:50 peat and sand mix may work better at first, but the peat breaks down and builds up salts over time, so its own guide prefers a much sandier 20:80 mix in a tray of water. The ICPS stresses the same point for Mexican butterworts and Heliamphora: match the mix to how you water. Looser mixes need more frequent watering.
Peat-Free Options
Tick “Show peat-free recipes only” to see the recipes in our sources that contain no peat. They are pure sphagnum moss for flytraps, subtropical sundews and terrestrial bladderworts, sphagnum and perlite for Nepenthes, all three Heliamphora mixes, and the small-plant mix of sphagnum and sand for Darlingtonia. Where a plant has no peat-free recipe in these sources, the calculator says so instead of inventing one.
Before You Mix
- Use ingredients with no added fertilizer. Sarracenia Northwest warns against ordinary potting soil, compost and fertilized products, and the ICPS says to read the bag.
- The ICPS recommends silica sand and warns against non-silica sand for sundews; it adds that orchid bark varies in quality and may contain fertilizer.
- Water the plants with pure water. Our water checker tests a TDS reading against the published limits.
Related Guides
- Best potting mix for Nepenthes
- Butterwort soil mix
- Cephalotus soil mix
- How to repot a Venus flytrap
- How to repot and divide Sarracenia
- Sundew care
Sources
- International Carnivorous Plant Society, Growing Dionaea [carnivorousplants.org/grow/guides/Dionaea]
- International Carnivorous Plant Society, Growing Sarracenia [carnivorousplants.org/grow/guides/Sarracenia]
- International Carnivorous Plant Society, Growing subtropical Drosera [carnivorousplants.org/grow/guides/SubtropicalDrosera]
- International Carnivorous Plant Society, Growing Drosera binata [carnivorousplants.org/grow/guides/Dbinata]
- International Carnivorous Plant Society, Growing pygmy Drosera [carnivorousplants.org/grow/guides/PygmyDrosera]
- International Carnivorous Plant Society, Growing Cephalotus [carnivorousplants.org/grow/guides/Cephalotus]
- International Carnivorous Plant Society, Growing Mexican Pinguicula [carnivorousplants.org/grow/guides/MexicanPinguicula]
- International Carnivorous Plant Society, Growing temperate Pinguicula [carnivorousplants.org/grow/guides/temperatePinguicula]
- International Carnivorous Plant Society, Growing Heliamphora [carnivorousplants.org/grow/guides/Heliamphora]
- International Carnivorous Plant Society, Growing Darlingtonia [carnivorousplants.org/grow/guides/Darlingtonia]
- International Carnivorous Plant Society, Growing terrestrial Utricularia and Genlisea [carnivorousplants.org/grow/guides/TerrestrialUtriculariaGenlisea]
- Sarracenia Northwest, Venus flytrap care [growcarnivorousplants.com/venus-flytrap-care]
- Sarracenia Northwest, Sarracenia care [growcarnivorousplants.com/sarracenia-care]
- Sarracenia Northwest, Nepenthes care [growcarnivorousplants.com/nepenthes-care]
This tool is editorially reviewed and its recipes are checked against the cited sources. Last reviewed: October 2026.