Sick of watching your cacti sulk or rot in soggy “all-purpose” potting mix?
This guide shows you exactly how to blend a fast-draining, mineral-rich cactus soil from ingredients you can grab at Bunnings or order in a click from Dr Greenthumbs. Scroll for the recipe, common mistakes, a quick video demo, and the fastest shortcut if you’d rather go straight to a pro-blended mix.
Cactus Soil Basics
Cacti hail from arid zones where rain drains through gravel in minutes. To mimic that in a pot you need a light, gritty medium with 70 – 80 % mineral content. A moisture-holding peat mix spells certain rot in our humid Aussie summers. Aim for:
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Rapid drainage: water should disappear through the pot in 5 sec.
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Air pockets: oxygen keeps roots alive and prevents anaerobic pathogens.
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Slight acidity – neutral pH (6.0-6.5) helps nutrient uptake.
Shortcut: If you want a mineral-leaning base without the measuring, start with the ready-made Mineral Based Soil and tweak with extra pumice or zeolite to taste.
Exact DIY Recipe For Dry Lovers (Makes ~5 L)
|
Ingredient |
Metric |
Imperial |
Why |
|
Pumice (3-5 mm) |
2 L |
8 cups |
Creates macro-porosity & wicks excess water |
|
Perlite (coarse) |
1 L |
4 cups |
Ultra-light, boosts drainage further |
|
Washed coarse sand |
1 L |
4 cups |
Adds weight so tall columnars stay upright |
|
High-grade zeolite |
0.5 L |
2 cups |
CEC buffer stores calcium & magnesium |
|
Sieved coco coir |
0.5 L |
2 cups |
Minimal organic fraction for micro-life |
Optional boosts
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1 tbsp Root Roids for mycorrhizal kick-start
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Pinch of slow-release mineral fertiliser
Printable card: copy the table, laminate, stick to your shed wall.
Mixing Instructions
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Sanitise your tub and trowel with 3 % hydrogen peroxide.
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Layer ingredients dry, largest particles first.
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Stir for one full minute – aim for a uniform texture.
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Moisten lightly until the mix just darkens; it should crumble if squeezed.
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Pot up; leave 1 cm rim space for top-dressing.
Why These Ingredients Work
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Pumice & perlite are inert, meaning they don’t break down and collapse over time.
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Zeolite acts like a smart sponge, trading nutrients with roots on demand.
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Coco coir replaces peat (better for the planet) and hosts beneficial microbes.
Need everything in one go? Check out the Cactus & Succulent Soil Builder DIY Kit – pre-weighted bags plus a recipe card let you skip the scales.
Common Mistakes & Quick Fixes
|
Mistake |
Symptom |
Fix |
|
Using peat-heavy potting mix |
Mushy brown roots |
Repot into recipe above; cut away rot |
|
Skipping top dressing |
Algae, fungus gnats |
Add 5 mm grit or crushed granite |
|
Over-watering |
Wrinkled yet blackened stems |
Water only when mix is bone dry 5 cm down |
|
No drainage hole |
Base rot |
Always use a pot with at least one 8 mm hole |
When to Buy Pre-Made Mix
-
New growers wanting zero guesswork
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Indoor keepers who water on autopilot
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Collectors of grafted or rare species worth the extra insurance
Grab our Cactus & Succulent Potting Mix – 5 L, or stock up with the value Buy 2 Get 1 Free bundle if you’ve got a greenhouse full of spiky friends.
Frequently Asked Questions
Can I reuse old cactus soil?
Yes, if it still drains fast. Sieve out roots, bake at 90 °C for 30 min to sterilise, then refresh with 30 % new pumice.
Is garden sand okay?
Only if it’s coarse and washed. Fine beach sand compacts and suffocates roots.
How often should I fertilise?
In the growing season (spring–summer) apply a half-strength mineral feed monthly.
Do I need to adjust pH?
The above recipe lands around 6.3. If you add limestone chips the pH will slowly rise, so test yearly.
Blending your own cactus mix is cheaper than coffee‐shop succulents and gives you total control over drainage and nutrients. Follow the metric recipe, dodge the common mistakes, and your cacti will charge into growth come spring. If mixing isn’t your jam, let Dr Greenthumbs do the dirty work – our full cactus soil collection has a blend for every grower.
Happy potting, legends! 🌵
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