Journal/Care Basics · 6 min read
Potting Soil Explained: What Mix Each Plant Needs
Not all potting mix is created equal. Learn what perlite, bark, coir, and peat do — and the exact ratios for aroids, succulents, ferns, and orchids.
Quick answer
Standard bagged potting mix is too dense for most houseplants. Aroids (Monstera, philodendron) want 3 parts mix : 2 parts orchid bark : 1 part perlite. Succulents want 1 part mix : 1 part perlite : 1 part coarse sand. Orchids grow only in bark, not soil.
The single biggest upgrade you can give most houseplants isn't a bigger pot or more light — it's the right soil. Off-the-shelf 'houseplant compost' is often too fine and holds water like a sponge.
What each ingredient does
- Peat / coco coir — the water-holding base. Coir is renewable; peat is not.
- Perlite — white puffed volcanic rock. Creates air pockets and drainage.
- Orchid bark — coarse chips of fir bark. Adds huge air gaps for chunky-loving aroids.
- Coarse sand / grit — density and drainage for succulents.
- Worm castings — a small hit of gentle organic nutrients.
- Activated charcoal — optional; helps keep terrarium soils fresh.
Mixes by plant group
DIY potting mix ratios by plant type
| Plant group | Base mix | Perlite | Bark | Sand |
|---|---|---|---|---|
| Aroids (Monstera, Philodendron, Pothos) | 3 parts | 1 part | 2 parts | — |
| Ferns | 2 parts | 1 part | — | — |
| Succulents & cacti | 1 part | 1 part | — | 1 part |
| African violets | 2 parts | 1 part | — | — |
| Orchids | — | — | 3 parts (medium bark) | — |
Signs your soil is wrong
- Water pools on top and takes minutes to soak in — too compacted, needs perlite.
- Soil stays wet for over a week — not enough drainage, add bark or perlite.
- Soil dries out within a day — either the pot is too small or the mix is too airy.
- White fuzz on top — usually harmless mould from a mix too fine and too damp.
Peat, coir, and the sustainability question
Peat bogs are massive carbon stores and take thousands of years to form; harvesting them for potting compost is now restricted or banned in many countries. Coconut coir is a renewable by-product of coconut processing and behaves almost identically. If you have a choice, choose coir.
PlantMe recommends a specific soil recipe per species when you identify it — no more guessing whether your fiddle needs cactus mix (it doesn't).
Frequently asked questions
Can I use garden soil for houseplants?
Almost never. Garden soil compacts in pots, drains poorly, and can bring in pests and pathogens. Always use a sterile potting mix indoors.
How long does potting soil last in a pot?
The physical structure breaks down over 18–24 months and starts holding too much water. Repot with fresh mix at that point even if you're not sizing up.
Is 'succulent soil' from the shop good enough?
Usually it's ordinary compost with a token amount of sand. Add an equal volume of perlite before using it — your succulents will drain properly and last years longer.
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