Are you looking for a quality potting mix recipe? My early experiences with bagged potting mixes were not happy ones. With a sea of choices, clueless salespeople and confusing labels, I made more than one bad choice. Maybe you have too!

Easy DIY Potting Mix Recipe: I fried my seedlings in what I thought from the label was 'potting mix with fertiliser' but was actually almost 100% fertiliser; starved my plants with the next bag that didn't have any food in it at all; and another bag was virtually dead dirt that wouldn't grow anything.

I fried my seedlings in what I thought from the label was ‘potting mix with fertiliser’ but was actually almost 100% fertiliser; starved my plants with the next bag that didn’t have any food in it at all; and another bag was virtually dead dirt that wouldn’t grow anything.

 

I got so seriously cheesed off wasting time and money with ‘dried arrangements‘ as a result. So I decided to make my own mix. It had to be better than going through all that pain!

Now, I try to be self-reliant and budget conscious where possible, by making my own supplies. If you don’t already, give home made potting mix a go. It’s easy, saves you money and a whole lot of headaches!

 

The ‘Dirt’ on Commercial and Soilless Potting Mixes


  • Surprisingly, the old adage ‘You get what you pay for’ doesn’t always apply. You often take ‘pot’ luck!  Gardening Australia ran some potting mix tests that proved this is the case. Even their seasoned experts were surprised by the results.

 

Quality bagged mixes can be quite expensive (when you add up ingredients, packaging, transport, marketing costs, retail margins, etc). Problem is - you often don't know what you've paid for until you've opened and used it!

Quality bagged mixes can be quite expensive (when you add up ingredients, packaging, transport, marketing costs, retail margins, etc). Problem is – you often don’t know what you’ve paid for until you’ve opened and used it!

 

  • Quality varies tremendously from certified organic products with strict standards to unlabelled contents of questionable origin and quality.
  • Poor labelling leaves consumers in the dark.
  • Peat and bark (commonly used ingredients) tend to become hydrophobic (water-repellent) as their moisture content drops to below 30%.

 

Many use non-renewable resources that impact the environment like peat moss (expensive; breaks down too quickly; and compacts easily reducing aeration and drainage).

Many use non-renewable resources that impact the environment like peat moss (expensive; breaks down too quickly; and compacts easily reducing aeration and drainage).

 

  • May include chemical polymers in wetting agents to compensate for the ingredients that are often hard to wet.

 

The most common ingredient is cheap composted pine bark which can be quite acidic & breaks down quickly, causing the soil structure to collapse. It also consumes nitrogen in your mix so has to be compensated for, with added fertilisers.

The most common ingredient is cheap composted pine bark which can be quite acidic & breaks down quickly, causing the soil structure to collapse. It also consumes nitrogen in your mix so has to be compensated for, with added fertilisers.

 

On the up side, commercial mixes are sterile, disease free and very convenient as you just open the bag!

 

So Why Make Your Own Potting Mix?


  • SAVE MONEY.  Potting mix bags range in price but you can ALWAYS make your own premium quality potting mix cheaper!
  • CONVENIENCE. Making a batch and storing it saves time. This way, you always have some on hand for mini projects. You don’t have to make it from scratch every time. Make up just the quantity you need.
  • SAFE INGREDIENTS. Many non-certified organic commercial mixes contain water crystals or soil wetters. These are made from chemical polymers. After researching the dangers of these, I’ve decided not to use or recommend such products. By making your own potting mix recipe, you know exactly what’s in it and can control the outcome you want.
  • SELF-RELIANCE. Making your own supplies is incredibly satisfying and you can share these skills with others.
  • LONGER LASTING. By choosing the right ingredients, you will get more mileage out of your own potting mix recipe, than a bagged mix based on bark. This ingredient quickly decomposes and becomes moisture resistant.

 

I've tried lots of different potting mix recipes with varying success rates. Now I just use a basic mix I know is reliable and long lasting - it's a starting point so feel free to try it out and experiment!

I’ve tried lots of different potting mix recipes with varying success rates. Now I just use a basic mix I know is reliable and long lasting – it’s a starting point so feel free to try it out and experiment!

 

The Role of Potting Mix Ingredients

 

An ideal general potting mix should be:

  • light and airy (so plants can easily take root and access oxygen in the soil);
  • long-lasting (won’t break down or become compacted);
  • moisture-retentive (hold water to save you money watering too frequently);
  • and contain some nutrient value (save you fertilising too often).
Potting Mix Recipe: I think of it like baking a cake - each of the ingredients plays an important function. In a typical cake mix, there are wet and dry ingredients, those that bind it together and make it rise. If an ingredient is missing, you can't expect successful results!

I think of it like baking a cake – each of the ingredients plays an important function. In a typical cake mix, there are wet and dry ingredients, those that bind it together and make it rise. If an ingredient is missing, you can’t expect successful results!

 

Similarly, in your potting mix recipe, you need ingredients that provide different roles. These include drainage, aeration, water and nutrient retention, plant food, support, microbes and sometimes, thermal insulation.

 

“Some ingredients perform multiple roles and I’ve chosen mine carefully to minimise cost and maximise the benefits.  This mix is suitable for use in pots, hanging baskets and gardens.”

 

Basic Potting Mix Recipe

I like to keep things simple. Whilst there’s no “one size fits all” potting mix recipe that is perfect for ALL plants, I believe every gardener should learn the basics to start with. When you’re confident after making a few potting mix batches, experiment! Try using more or less of the ingredients to suit your own needs. Or substitute with resources you have easy access to.

 

This basic potting mix recipe is a starting point.

This basic potting mix recipe is a starting point.

 

Potting Mix Recipe Materials

You’ll need:

  • a container for measuring;
  • a large bucket for mixing in;
  • access to water (kettle and hose/watering can);
  • sieve;
  • a small fork and trowel;
  • a container for pre-soaking the coir peat; and
  • your ingredients.

 

Safety First!

Precautions to take when making your own potting mix:

  1. To prevent inhaling dust or organic particles and the risk of any disease, wear a particulate face mask when working with organic materials.
  2. Wear suitable protective clothing and gloves. Wash your hands afterwards.
  3. Avoid making your potting mix on a windy day.
  4. Wear safety glasses to protect your eyes from dust.
  5. Use a spray bottle to mist water over dusty ingredients.

 

Remember to wear suitable protective clothing when making potting mix.

Remember to wear suitable protective clothing when making potting mix.

 

Potting Mix Recipe Ingredients

Ideally, source your ingredients from your own garden, locally and choose organic where possible. There are also many sustainable, low-cost options online. These are a few products that I’ve hand picked for quality, safety and value.

 

CLICK BELOW for potting mix recipe ingredients

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  • 1 part pre-soaked Coir Peat. Coir peat is a cheap, but long lasting renewable resource. This is a more responsible environmental choice than peat moss. Coir peat is a waste by-product from the coconut-processing industry. The finer product left behind after the husk fibre is processed, is called ‘coconut coir’ or ‘coir peat.’ Don’t confuse this with peat moss, a very unsustainable resource!

 

Potting Mix Recipe Ingredient: Coir peat brick - this small brick makes up 9 litres when rehydrated

Coir peat is available in a convenient dry, lightweight compact block (in various sizes). It’s sold online, at garden centres, supermarkets, produce and hardware stores. It provides aeration; water holding capacity and bulk to the mix.

 

  • 1 part Vermiculite* (Grade 3 is a good size).  Vermiculite is the silvery grey coloured particles you often see in potting mixes. It is a natural volcanic mineral that has been expanded with heat to increase its water holding capacity. It can come from a variety of sources around the world. You can also purchase asbestos-free vermiculite online.

 

Vermiculite close up

The flaky particles soak up moisture and nutrients and keep them in the mix so the plants can access them. It’s lightweight; inorganic so is a permanent ingredient that will not deteriorate or lose volume in the mix; clean; odourless; non-toxic; sterile (no pathogens) and won’t become mouldy or rot.

 

  • Vermiculite has a moderate CEC (cation exchange capacity). This means it can hold/make available minerals to the plants.  [* If unavailable, use coarse sand – see Tips]
A 4 litre icecream tub is a good size container to use for measuring small quantities of mix.

I prefer this medium to coarse washed river sand because it provides excellent drainage and has great moisture and mineral retaining properties whereas sand doesn’t. It also helps aerate plant roots, has good pore space and is a thermal insulator. Depending on which brand you buy, the pH may be a little alkaline.

 

Sieving compost - I use a metal sieve which sits just inside the lip of a flexible bucket and makes it easy to remove any lumpy bits!

Compost retains minerals, provides moisture and plant food, microbes and improves the structure of the growing media. It also acts as a buffer to changes in pH and suppresses disease.

 

  • 1/2 to 1 cup* Worm Castings or Vermicast (humus). Ideally you will have your own worm farm to add this perfect humus to your mix. Note: * this is an approximate quantity based on making 36 litres (4 x 9 litre buckets) of potting mix using a 9 litre brick of coir peat. Feel free to add more if you have it! If you can’t access vermicast, you can buy worm castings or use some humus from the bottom of your compost pile that is most decomposed or use good quality compost.

 

CLICK BELOW for worm farm and composting resources

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Humus from the worm farm ready for use.

Humus has so many benefits including the capacity to hold nutrients and supply them to your plants; incredible moisture retention capacity (holds 80-90% of its weight in water); prevents leaching; provides beneficial microbes; is a plant food source; a buffer for toxic metals and chemicals; and has the optimum soil crumb texture.

 

  • A “part” can be whatever quantity you need: a small scoop or icecream tub; a 9 litre bucket or even a wheelbarrow depending on how much potting mix you require. I make 60 litres at a time in a large flexible bucket and store the rest till needed.

 

Potting Mix Recipe Method

 

STEP 1: Pre-soak coir peat in warm water in a large plastic container. Tip: To rehydrate a 9L block requires 4.5L of water so you need a container bigger than a 9L bucket to work in (minimum 14L size).

 

Add HOT water to the coir peat block to speed up hydration.

When rehydrated according to the directions for the volume you are making, loosen and fluff with your trowel.

 

STEP 2: Mix equal quantities of pre-soaked coir peat and vermiculite (or coarse sand if using) together well in a large separate container.

 

Blend the coir peat and vermiculite together first.

I’ve found it easier to get an even mix by blending the coir & vermiculite together first.

 

STEP 3: Next, add the sieved compost and worm castings and combine thoroughly with (optional) nutrients.

 

Blend all the ingredients together well as you would when making a cake!

You may need to moisten lightly with a watering can until you can just squeeze a few drops of moisture out of the mix or it has a nice moist but NOT wet feel.

 

STEP 4: Check the soil pH with a meter.  Most plants require a pH of between 6.0 and 7.0. If you are growing vegetables, from my experience, they grow best in the range of 6.2 – 6.8 pH.

TIP: Store in a container WITH a lid. This stops your potting mix drying out if not using it all immediately.

Some plants do require a more acidic mix (e.g. azaleas, gardenias, rhododendrons and blueberries) to thrive. I've never had to adjust the pH using this recipe, however you may need to for what you are growing.

Some plants do require a more acidic mix (e.g. azaleas, gardenias, rhododendrons and blueberries) to thrive. I’ve never had to adjust the pH using this recipe, however you may need to for what you are growing.

 

How to Adjust the Soil pH

 

To raise the pH of potting mix by about one unit (make it more alkaline), add 1 – 1.5 grams of dolomite (lime)/litre of mix.

To lower the pH by about one unit (make it more acidic), add 0.3 grams of sulphur/litre of potting mix.

Keep the potting mix moist and recheck the pH again a few days later.

CLICK BELOW for a soil pH tester and nutrients you can boost your potting mix recipe with

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Add Nutrients (optional but recommended!)

 

I suggest you also add minerals and slow release organic fertilisers. You can blend these additional ‘ingredients’ into the mix all at ONCE. Then all you have to do is plant and water! The plants have everything they need to start growing.

Nutrients you can add:

  • Rock Minerals – Plants need a balance of minerals for health & reproduction – just like we do. About 1 cup of a balanced dry mineral or soft rock phosphate mix (or use crusher dust) or use according to the directions.
I've had good results with complete powdered organic fertilisers like Nutri-Store Gold, Organic Link, Searles Kickalong Organic Food as well as pelletized Organic Xtra fertiliser.

Depending on what I have available at the time, I add about a cup to provide plants with an immediate and slow release of food.

 

  • Seaweed & Fish – These provide essential trace elements. These can boost root growth, plant health, disease resistance, transplant shock and provide many other benefits. Good value certified organic products include Eco Seaweed (convenient powdered seaweed concentrate which is easy to add to the potting mix); Searles organic range of Kelp & Fish liquid products; and NatraKelp.

 

CLICK BELOW for potting mix resources

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My Potting Mix Recipe Tips


  • If you want fast results, soak your coir peat block in hot water to speed up hydration.
  • Coarse washed river sand (salt removed) or builder’s sand can be substituted for vermiculite. Sand is an alternative ingredient for drainage. Or to minimise cost, use a combination of both. “Coarse” is important. The rough shape and size of the individual grains of sand allow space for water to pass though. If the grains are too fine, smooth and round (like you find on the beach), water will cling to them and they’ll compact, drowning your plants.
  • Use sand if you need to weigh your container down. e.g. for a windy balcony so it is less likely to blow over. Add more sand for a faster-draining succulent mix.
  • Once you have potted up your plants, avoid letting the mix dry out. Coir peat holds moisture well, but if it really dries out over time, it can take time to re-wet thoroughly. Mulch really well.
  • Compost breaks down as the nutrients are used up by the plants. So the volume of mix in your pot will gradually drop. You will need to top up with additional fresh potting mix around your plants over time.
  • Some potting mix recipes suggest using perlite instead of vermiculite. However, I prefer not to use this due to the risk of Silicosis. Overexposure to dust containing microscopic silica can cause scar tissue to form in the lungs, reducing the ability to extract oxygen from the air. It’s wise to always use a protective particulate face mask when using organic materials.
  • When buying a commercial potting mix, look for the Australian Standards Mark (AS 3743) on the packaging. A black tick indicates a basic potting mix and a red tick has added fertiliser which means it will feed your plant for a period of weeks. If I buy a bag of commercial potting mix, I choose Searles. Alternatively, look for an equivalent quality guarantee in other countries.

 

So, that’s my take on potting mix! … What recipes do YOU use if you make your own potting mix? I’d love you to share your thoughts here.

Related Articles: Re-using Old Potting Mix | Frugal Gardening | Thrifty Recycling Tips for your garden.

 

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