Soil & Potting Mix Guide

Soil in a pot isn't just "the stuff the plant stands in" — it's the plant's entire home: water, air and food all come from there. A great many plant problems that look like watering problems are really soil problems.

What goes into a good potting mix

Every good mix does three jobs at once, and all three matter:

  • Holds moisture — so the roots keep getting water. Cocopeat, compost and leaf mould do this.
  • Lets excess water out (drainage) — so water doesn't sit. Sand, perlite, cinder or fine grit do this.
  • Provides air (aeration) — the gaps between soil particles, where roots breathe. This is the most overlooked part of all.

Alongside that you need nutrients (from compost or vermicompost) and a structure that won't compact into stone over the months. A good mix feels light, crumbly and airy in the hand — not sticky and heavy.

Why garden soil alone fails in a pot

The same soil works perfectly well in the ground — because there, insects, roots and natural drainage keep loosening it constantly, and excess water drains away into the earth below.

A pot is a closed box. In it, that same soil:

  • Compacts hard after watering, and on drying shrinks like stone away from the sides of the pot — after which water runs straight down the edge and the soil stays dry
  • Gives the roots no air — which is the root of root rot
  • Holds water at the top and lets it down only slowly
  • Can carry weed seeds, insects and fungus
  • Is heavy — a problem all of its own for a balcony or terrace

So you don't have to remove garden soil entirely — you have to lighten it. It should be one part of the mix, not the whole mix.

Drainage — the most important thing

  • The pot must have a drainage hole. This one thing saves more plants than anything else. Don't plant directly into a decorative pot with no hole — put a plastic pot inside, take it out to drain after watering, then put it back.
  • Tip out water collected in the tray within 15-20 minutes.
  • You don't need to fill a whole layer of stones at the bottom — in a large pot, a broken piece of earthenware or a little coarse material over the hole is enough to stop it blocking. Real drainage comes from the mix, not from a bottom layer.
  • Pot size: only 1-2 inches bigger. A much larger pot means more soil than needed, which stays wet for longer — root rot.
  • Pot material: terracotta breathes and dries faster (better for monsoon, and for people who tend to overwater). Plastic and ceramic hold moisture longer (useful in dry heat, but riskier).

A simple general-purpose mix

This works for most household plants. By volume:

  • 2 parts garden soil / loamy soil — structure and base
  • 1 part cocopeat — to hold moisture
  • 1 part compost or vermicompost — nutrients
  • 1 part coarse sand, perlite or cinder — drainage and aeration

How to make it: if you have a cocopeat block, soak it in water first and squeeze it out well. Mix everything dry on a sheet or in a tray, then dampen lightly. Squeeze the mix in your hand — if it forms a ball that breaks apart at a touch, it's right. If it forms a sticky ball, add more sand or perlite.

How to adjust: soil staying wet too long — increase the sand/perlite. Drying out too fast — increase the cocopeat/compost. These ratios aren't set in stone; adjusting them a little for the air and water in your own home is exactly the right approach.

Mixes for different plants

Succulents and cacti

Their original home is dry country — they need fast drainage, not moisture. The general mix is far too "wet" for them.

  • Roughly half coarse sand / cinder / perlite
  • 1 part garden soil
  • A little cocopeat or compost — very little

Don't use fine "beach sand", it compacts — you want coarse, gritty sand. A terracotta pot is best for these plants.

Flowering plants

They need energy, so slightly more nutrients and moisture — but standing water is still forbidden.

  • 2 parts garden soil
  • 1 part compost / vermicompost — a bit more than the general mix
  • 1 part cocopeat
  • 1 part sand / perlite

Flowering plants also benefit from light, regular feeding during the growing season — see the Fertilizer Guide.

Seeds (germination mix)

Seeds don't need nutrients to begin with — the seed carries its own food. What they need is soft, fine, consistently lightly-moist soil that delicate roots can push through easily.

  • 1 part cocopeat
  • 1 part fine compost or leaf mould
  • A little fine sand

Heavy garden soil and strong fertiliser don't belong in seeds — both stop germination. Keep the soil lightly moist, not wet, and press the seed in only as deep as the product says.

Remember: germination is not guaranteed on seeds — it depends on soil, temperature, moisture, depth and handling.

Indoor foliage plants

Indoors, soil dries slowly, so it's better to keep a little more drainage in an indoor mix — increase the sand/perlite share in the general mix. Overwatering is the commonest cause of death in indoor plants, and heavy soil is responsible for half of that.

Repotting basics

When it's needed

  • Roots are coming out of the drainage hole
  • Water sits on top and goes down very slowly
  • The plant looks far too big for its pot, or keeps toppling over
  • Growth has stopped even though light and water are fine
  • The soil has gone old and hard, or a white crust has formed on top

When not to

  • A newly delivered plant — wait at least 2-3 weeks. A plant can't take transit stress and repotting stress together.
  • When the plant is sick or stressed — except when treating root rot
  • In winter, when the plant is dormant. The best time to repot is the growing season.
  • Right in the middle of flowering — the plant may drop its buds

How to do it

  1. Water lightly a day before — the soil comes out of the pot more easily
  2. Take a new pot only 1-2 inches bigger, and make sure it has a drainage hole
  3. Don't pull the plant out by the stem. Tilt the pot to one side, tap the rim, and slide the plant out while supporting it
  4. Loosen the root ball slightly. If the roots are wound tightly in circles, open them gently, otherwise they'll keep growing in that same circle
  5. Cut away black, soft, foul-smelling roots — keep only firm, healthy ones
  6. Put some fresh mix in the new pot and set the plant in the middle — keep the plant at the same depth as before; the stem should not be buried in soil
  7. Fill mix around the sides and press lightly (don't ram it — the air gaps need to survive). Leave about an inch clear at the top so water doesn't spill over when you water
  8. Water thoroughly until it starts running out of the drainage hole
  9. After that keep it in shade for a week or two, and no fertiliser at all. Fresh mix already has nutrients, and delicate new roots get burned by fertiliser

After repotting, a few leaves may drop or the plant may droop a little — that's normal transplant shock. New growth can take a few weeks to appear.

Matching the mix to the plant

Fast-draining, succulent-type mix

Organic-rich, well-drained potting mix

Loamy soil for fruit plants in the ground or a large pot

  • Guava Lucknow-49 — full sun, 6+ hours; hardy and fast-growing.
  • Mango Alphonso (Grafted) — well-drained loamy soil, pH 5.5–7.5; NPK plus compost 2–3 times a year, extra potash at flowering.
  • Lemon Balaji — sandy loam; citrus needs micronutrients (zinc/iron) 3–4 times a year.

Browse: Indoor Plants · Fruit Plants · Flowering Bulbs

Read next

Watering Guide · Fertilizer Guide · Light Guide · Plant Doctor