Most houseplants die from root rot, not neglect — and the cause is usually the wrong soil. The bag of "potting soil" you buy at the hardware store is designed for outdoor gardens, not indoor pots. It holds too much water, drains too slowly, and it compacts over time. I've killed more plants with soggy soil than with dry soil, and I've learned that mixing your own soil is the single biggest upgrade you can make.

Here's how to mix soil for the three main categories of houseplants, with the ratios I use and why.

Why bagged potting soil isn't enough

Bagged potting soil is usually peat moss + some compost + maybe some perlite. It's designed to be cheap and versatile, but it has problems for indoor plants:

• It holds too much water. Peat moss is like a sponge. In a pot without drainage or in a low-light room, the soil stays wet for days. Roots need oxygen as much as water — wet soil = suffocated roots = root rot.
• It compacts over time. After a few months, the peat breaks down and the soil becomes dense. Water runs down the sides instead of soaking in. Roots can't penetrate the compacted layer.
• It doesn't drain well. Most bagged soil doesn't have enough perlite or bark for drainage. The water sits at the bottom of the pot, and the roots rot.

The fix: mix your own soil with the right balance of moisture retention, drainage, and aeration. It costs a little more upfront, but a bag of perlite and a bag of orchid bark last for years.

The ingredients

• Potting soil (base): any standard bagged potting soil. This provides the structure and some nutrients.
• Perlite: the white, lightweight rocks. It improves drainage and aeration. It doesn't break down over time. A bag lasts for years.
• Orchid bark: small chunks of bark (usually fir bark). It improves drainage and aeration, and it breaks down slowly over months. It's essential for chunky mixes.
• Worm castings: a gentle, organic fertilizer. It adds nutrients without burning roots. A little goes a long way — 1/4 cup per gallon of soil is plenty.
• Horticultural charcoal: optional, but it helps absorb excess moisture and prevents mold. It's especially useful for terrariums and pots without drainage.
• Coconut coir: an alternative to peat moss. It holds moisture but drains better, and it's more sustainable (peat moss is harvested from bogs). It's a good substitute if you want a more sustainable mix.

Mix 1: Tropicals (pothos, philodendron, peace lily)

This is the all-purpose mix for most common houseplants. It drains well but still holds enough moisture for tropical plants that like consistently moist (not wet) soil.

Ratio: 2 parts potting soil + 1 part perlite + 1 part orchid bark + 1/4 cup worm castings per gallon.

When to use: pothos, philodendron, peace lily, spider plant, calathea, prayer plant, peperomia, dracaena. Most plants you'd buy at a nursery fall into this category.

Why it works: the potting soil holds moisture, the perlite and bark improve drainage and aeration, and the worm castings add gentle nutrients. It's the mix I use for 80% of my plants.

Mix 2: Chunky aroids (monstera, philodendron, orchids)

This is a very chunky, well-draining mix for plants with thick, aerial roots. They need lots of air around their roots, and they hate sitting in wet soil.

Ratio: 1 part potting soil + 2 parts orchid bark + 1 part perlite + 1/4 cup worm castings per gallon.

When to use: monstera, philodendron (especially epiphytic types like Philodendron scandens), orchids, anthurium, aroids with aerial roots.

Why it works: the orchid bark provides structure and aeration, the perlite improves drainage, and the small amount of potting soil holds just enough moisture. It's the mix I use for my monstera and epiphytic philodendrons.

Mix 3: Succulents and cacti

Succulents and cacti need fast-draining soil that dries out quickly. Regular potting soil holds too much moisture and causes root rot. This mix is gritty and well-draining.

Ratio: 1 part potting soil + 2 parts perlite + 1 part coarse sand (or pumice) + 1/4 cup worm castings per gallon.

When to use: succulents (echeveria, haworthia, jade, string of pearls), cacti, aloe vera.

Why it works: the perlite and sand provide excellent drainage, the small amount of potting soil holds just enough moisture, and the worm castings add gentle nutrients. It's the mix I use for all my succulents and cacti.

Note: you can also buy pre-made cactus/succulent mix, but it's often just potting soil with a little sand. It's cheaper to mix your own, and you get better drainage.

Mix 4: Ferns and moisture lovers

Ferns, calatheas, and other moisture-loving plants need soil that stays consistently moist but not waterlogged. This mix holds more moisture than the tropical mix.

Ratio: 3 parts potting soil + 1 part perlite + 1 part coconut coir + 1/4 cup worm castings per gallon.

When to use: ferns (boston fern, maidenhair fern), calatheas, prayer plants, fittonia, polka dot plant.

Why it works: the extra potting soil and coconut coir hold moisture, the perlite provides some drainage, and the worm castings add gentle nutrients. It's the mix I use for my ferns and calatheas.

Tips from my mistakes

• Don't skip the perlite. I used to use straight potting soil and wondered why my plants rotted. Perlite is the single most important ingredient for drainage. Don't skip it.
• Don't overdo the worm castings. A little goes a long way. Too much worm castings can burn roots and attract fungus gnats. 1/4 cup per gallon is plenty.
• Mix in a big container. I use a 5-gallon bucket. Add the ingredients, mix with your hands or a trowel, and store in a sealed bag. It keeps for months.
• Moisten the mix before potting. Dry peat moss and coconut coir are hydrophobic — water runs off the surface. Moisten the mix with water before potting so it absorbs evenly.
• Repot every 1–2 years. Soil breaks down over time. The bark decomposes, the perlite sinks to the bottom, and the soil compacts. Repot every 1–2 years with fresh mix.
• Don't use garden soil. Garden soil is too heavy for pots, it compacts, and it may contain pests or diseases. Always use potting soil as the base.

Mixing your own soil is the single biggest upgrade you can make for your houseplants. The tropical mix (2:1:1 soil:perlite:bark) works for 80% of plants, and the succulent mix (1:2:1 soil:perlite:sand) works for the rest. If you're not sure when to water after repotting, my watering calculator builds a schedule based on your plant type, pot size, and light conditions. And if you want to know what the soil should feel like at each stage, my soil moisture guide explains the finger test and moisture meter readings.

I've killed more plants with soggy soil than with dry soil. This site is one person writing about plants — not a nursery, just what actually worked.

The fix for almost every watering mistake is checking the soil before you water. Here's my soil moisture guide — the finger test, what a moisture meter should read, and what dry actually feels like.