Potting mix is not soil. Garden soil in a pot compacts, drains badly, and carries pests and weed seeds — which is why plants in garden soil in containers usually struggle. A good potting mix is a deliberate blend: something that holds moisture, something that drains, something that feeds, and something that keeps air around the roots. The standard homemade recipe is roughly equal parts compost or coir, perlite or bark, and a moisture-holding ingredient such as vermiculite or more compost — and the exact balance depends on the plant. This guide gives the base recipe, variations for different plants, how much to make, and the mistakes that kill container plants.
Making your own mix is cheaper than buying bagged mix in bulk, and it lets you adjust for the plant instead of using one bag for everything. It also avoids the variability of cheap bagged mixes, which can be mostly peat dust, mostly bark, or full of weed seeds. The trade-off is that you need the ingredients and a place to mix them — a tarp on the ground and a few bags of materials is enough to start.
The base recipe
The all-purpose potting mix that suits most houseplants and container vegetables is:
- 1 part mature compost — feeds the plant and holds moisture and nutrients.
- 1 part coco coir or leaf mould — holds moisture, keeps the mix light, and gives structure.
- 1 part perlite — drains water and keeps air around the roots.
Mix the three parts by volume — a bucket as a measure works well — and wet the mix lightly before filling pots, so dust does not rise and the ingredients settle together. That 1:1:1 blend is a good default for plants such as monstera deliciosa, golden pothos, tomatoes in containers, lettuce and most herbs. For a fuller discussion of the mineral ingredients, see our perlite vs vermiculite and coco coir for plants guides. Use the potting mix calculator to work out quantities for the number of pots you are filling.
If you prefer a peat-free commercial mix as a base, you can use it as the compost part of the recipe and add perlite and coir to improve it — many bagged mixes are too dense on their own and benefit from a third of perlite added. And if you use your own compost, sieve it first through a 1 cm mesh to remove lumps, sticks and stones that make potting awkward.
Recipes for different plants
Succulents and cacti. Roughly 1 part compost, 1 part coarse perlite and 1 part grit or coarse sand by volume. No coir, no vermiculite — these plants need the mix to dry fast. Use a pot with drainage holes and never let the plant sit in water.
Seed starting. Use our dedicated seed starting mix instead: roughly 2 parts fine coir, 1 part fine compost and 1 part fine vermiculite, sieved and with no fertiliser added. Seedlings need a fine, gentle mix, not a general potting mix.
Moisture-loving houseplants. For ferns and similar plants, use roughly 2 parts coir, 1 part compost and 1 part vermiculite, with only a little perlite. The mix should stay evenly damp, not wet.
Orchids. Orchids need a very open mix: roughly equal parts coarse bark, coarse perlite and charcoal, with no compost or coir at all. Most orchids are epiphytes that grow on trees in the wild, so their roots need air more than they need soil.
Acid-loving plants. For blueberries in containers, use roughly 2 parts composted bark, 1 part leaf mould and 1 part perlite, with no lime, and water with rainwater. See our growing blueberries guide.
Vegetables in containers. Use the base 1:1:1 recipe, but add a handful of slow-release organic fertiliser per 10 litres of mix, because container vegetables are heavy feeders and the mix alone will not feed them all season. See our fertilizing vegetables guide.
How much mix do you need?
Work out the volume of each pot before you buy ingredients. A pot's volume in litres is roughly its diameter in centimetres squared, times its height, times 0.0008 — but the easy way is to use the potting mix calculator, which does it for you. As a rough guide, a 30 cm pot holds about 10 litres, a 25 cm pot about 7 litres, and a 15 cm pot about 2 litres. Buy ingredients in bulk if you have many pots: a 100-litre bag of perlite and a few bricks of coir go a long way, and homemade mix is usually cheaper than bagged mix once you are filling more than a dozen pots. Store unused ingredients dry and under cover — damp compost and coir go mouldy in storage, and wet perlite is heavy to carry.
Step-by-step: making and using potting mix
1. Gather the ingredients. Sieve your compost, soak and rinse coir bricks if you use them, and have perlite and any extras ready. Work outdoors or in a ventilated area, and wear a mask and gloves.
2. Measure by volume. Use a bucket as a measure and mix in the proportions for your plant. Mix on a tarp or in a large tub, turning the pile several times until it is even.
3. Wet the mix lightly. Sprinkle water over the mix and turn it again until it is damp like a wrung-out sponge. Dry mix is dusty and does not settle properly around roots; soaking wet mix is heavy and compacts.
4. Fill the pot. Put a piece of broken pot or mesh over the drainage hole — not a layer of gravel, which does not improve drainage and wastes space. Fill the pot two-thirds full, set the plant in, and fill around the roots, firming gently. Leave 2–3 cm below the rim for watering.
5. Water thoroughly. Water until it runs from the drainage hole, so the mix settles around the roots. Top up the mix if it sinks.
6. Mulch the surface. A thin layer of bark, coir or pebbles on the surface reduces evaporation and keeps the mix from crusting. Keep mulch away from the stem.
How long potting mix lasts
Potting mix breaks down over time: compost rots away, coir compacts, and the mix loses structure and nutrients. Most container plants need repotting every one to two years, and the old mix should not simply be reused as it is — it is depleted, compacted, and may carry pests or disease. Refresh it by mixing one part old mix with one part fresh compost and a handful of perlite, and use the refreshed mix for hardy outdoor containers rather than for seedlings or sensitive houseplants. Spent mix can also go on the compost heap or be dug into garden beds, where it adds organic matter. Houseplants should be repotted when roots circle the pot or poke out of the drainage holes, or when water runs straight through without wetting the mix — both signs the mix has broken down. See our fertilizing houseplants guide for feeding between repottings.
What never to put in a potting mix
Never use garden soil on its own in a pot: it compacts, drains badly, and carries weed seeds and pests. Never use fresh manure, which burns roots and can carry pathogens — compost it first. Never use fresh bark or wood chips in the mix, which temporarily rob nitrogen; use composted bark only. Never use fine sand, which fills air spaces and makes the mix dense. Never use ash in large amounts, which raises pH sharply. And never add garden lime to a mix for acid-loving plants. If you are unsure whether an ingredient is safe, check your local extension service for advice.
Common mistakes
The most common mistake is using garden soil in pots, which is the single biggest cause of failing container plants. The second is making a mix that is too dense — too much compost and not enough perlite — so roots sit in wet, airless mix and rot. The third is the opposite: too much perlite and no compost, so the mix dries in hours and holds no nutrients. The fourth is not feeding container plants, because a pot's small volume of mix runs out of nutrients within weeks. The fifth is reusing old mix without refreshing it. And the sixth is using a pot with no drainage hole, which turns even a perfect mix into a swamp.
Safety notes
Wear gloves and a dust mask when handling dry perlite, vermiculite, coir and compost — all of them raise dust that irritates eyes and lungs. Wet ingredients down before mixing. Wash your hands after handling compost and manure, and use only mature, well-rotted manure. Keep bagged mixes dry in storage, and discard any mix that smells sour or has visible mould. If you are unsure about a product, check your local extension service for advice.
Frequently asked questions
What is the best homemade potting mix recipe?
For most plants, roughly equal parts mature compost, coco coir or leaf mould, and perlite by volume. Adjust for the plant: more perlite and grit for succulents, more coir and vermiculite for moisture-lovers, and a dedicated fine mix for seeds.
Can I use garden soil in pots?
Not on its own. Garden soil compacts in pots, drains badly, and carries weed seeds and pests. If you want to use it, mix one part garden soil with one part compost and one part perlite, and sieve it first — but a soil-free mix is usually more reliable.
How often should I replace potting mix?
Repot most container plants every one to two years with fresh mix. The old mix can be refreshed with compost and perlite for hardy outdoor containers, or added to the compost heap or garden beds.
Do I need to fertilise plants in homemade potting mix?
Yes. The compost in the mix feeds plants for a few weeks, but containers run out of nutrients quickly. Feed every two to four weeks through the growing season with a balanced liquid feed, or mix slow-release organic fertiliser into the mix at potting time.
Why is my potting mix staying soggy?
The mix is probably too dense — too much compost or coir and not enough perlite — or the pot has no drainage hole. Repot into a freer mix with more perlite and make sure water can drain away. Roots sitting in soggy mix will rot, so act quickly.