You want the best potting medium? Awesome, me too (that’s why I wrote this post–so I can remember it the next time I have to make it because I almost lost it). Before we get to the recipe, it’s helpful to understand what makes a soil “good” for plants in the first place; from this understanding we can extract HOW we make a great substrate.
Don’t care about “the what”? Feel free to skip to my “SUPER-AMAZING, Magical, Best Potting Mix Recipe” down below.
In order to make a really great and amazingly-awesome soil for our plants, we’ve got to overcome these three challenges:
1) Air Flow + Fast Draining
If we want our plant to be healthy and happy we need their roots to be healthy and happy. To do that, we make sure the root environment is fresh and clean which means we need a soil that allows for good water flow during watering and encourages air flow between waterings. If the medium doesn’t drain effectively and water fills the air space and makes a muddy slurry, then the dirt becomes stagnant and sour and THAT is a really bad environment for roots.
We can prevent this in two ways:
- By creating a soil that can take a lot of water but then quickly drain and as it drains, flush away any access junk (calcium from our tap water, extra fertilizer salts, anaerobic bacteria etc); and
- By creating a “breathing action” within the soil. We do this by repeating a cycle of wetness followed by drying. This wet-dry cycle brings fresh air through the root zone two times per week (when we water, and then when it dries), keeping the root zone fresh and well oxygenated all the time.
*Note: It’s still important that the soil retains moisture between waterings or the root zone will dry too quickly and kill our roots just as easily as stagnant conditions can choke the roots out. We find this balance by using a mix of organic and inorganic additives. Let’s take a look at those options.
The Best Potting Mix Needs: Organic Compounds
Include: peatmoss, sphagnum moss, loam/top soil, and bark/wood chips.
Organic compounds will hold water and break down over time, releasing nutrients back to the plant.
The Best Potting Mix Also Needs: Inorganic and Structure-Providing Fillers
Include: turface, leca, pumice, perlite, lava rock, and sand.
Inorganic compounds open the soil up, provide structure, improve drainage and allow for airflow that has the effect of improving oxygen at the root zone
The perfect balance will depend on your conditions. Dry climates will cause water to evaporate faster and growers from these regions should use a potting media will with more organic compounds which will slow evaporation. Those who live and grow in a humid climate will want to use more inorganic compounds because they encourage airflow which is required when evaporation rates are slower. If you want the specifics, I’ve included my “go-to recipe” at the bottom of this article as a good starting point that you can tweak on your own to fit your climate or type of plant.
2) Nutrients / Fertilizers (Short Term + Long Term)
Plants need nutrients. Duh, right? Well yeah, but it gets a bit complicated because not all nutrients are created equally. Most standard fertilizers don’t include all the micro nutrients your plant will need for the totality of its life and further to that, peatmoss alone (the primary ingredient in most potting souls) is very low in nutrients. We want to get all of those nutrients into our plant so we add a range of nutrient sources to the dirt.
Quick Access Fertilizers – Easy Nutrients
– Standard NPK Fertilizer at each watering.
– Micronutrients additives that are not added at every watering but instead at extended intervals (like once a month, once a quarter, or once a year). These micronutrient requirements will depend on the individual plant (eg — iron for some amazon basin plants), but in general you likely won’t need to worry about this, especially if you’re using this potting mix
Intermediate Access Nutrients
These are nutrients that require some level of biological interaction (breakdown of) to occur at the soil level. We add these to the soil to promote good bacteria and fungus, AND to provide a longer-term source of Nitrogen, Potassium and Phosphorus. Those additives include compost, bloodmeal, and bonemeal which you should be able to get easily at your local garden centre.
Slow Release Fertilizers – Long-Term Nutrients & Micronutrients
These are additions that will start breaking down and becoming available to your plant months to years (yes YEARS) later. With this medium, I don’t have to repot my plants for 2 years or more, and that’s why I love it. Those slow release nutrient sources are rock dust and wood/bark chips. You’re welcome by the way–this is mostly my MOST secret ingredient!
3) WATER! DO NOT LET IT FULLY DRY OUT
This has nothing to do with the soil ingredients, but it’s a very important rule that’s often not understood by people who don’t have a “green thumb”. Many plants cannot recover from desiccated roots. For those that can recover, we risk setting them back if their roots dry out too much. The takeaway: avoid letting the soil completely dry out at all costs and always water as it approaches dryness, not when it is dry. Typically this should be once a week.
Here are a few tips on watering your plants:
– When you water, water liberally. Get the substrate soaking wet and flush all the junk out. Think of this as a cleaning process…wash all the grossness out! (But leave the dirt in)
– Add “helper plants” that will tell you the soil is starting to dry before it’s too dry. “Wilters”—plants that sulk and tell you when the soil is getting too dry with their droopy leaves. Good options are: Peace Lilies / Anthuriums, and Kohleria (a taller version of an African violet).
The SUPER-AMAZING, Magical, Best Potting Mix Recipe
This recipe works for tropical plants, succulents, and cactus. I use this on my Australian Finger Limes, Anthuriums, Gesneriads/African Violets, Hoyas, Epiphyllums, Sansiverias, Monstera Deliciosa, and pretty much any other plant that isn’t an orchid.
Note: If you can’t find any of the following items (like turface), then you can adjust the ratio in favour of another ingredient; it’s not the end of the world. The more of this that you can add, the better it will be for the overall mix, but don’t stress. This mix at any ratio is going to be better than whatever “out of the bag” potting mix you’ve been using.
Also Note: I’ve made this recipe as percentages. If you want direct measurements, use cups and remove a “0” from the %.
Ie. 40% == 4cups
Goal: 60% organic / 40% inorganic + Slow Release Ferts
– 40% Peatmoss
– 20% Compost, Manure
– 20% Topsoil from outside
– 20% Bark
– 50% Perlite
– 35% Sharp-medium grit and porous rock (turface, pumice, or lavarock).
– 15% Sand
Slow Release Nutrients
– 1tsp/gallon(4L) Rock Dust
– 1/2tsp/gallon(4L) Bloodmeal
– 1/2tsp/gallon(4L) Bonemeal
Step 1. Mix the organic ingredients together and add a good amount of water to hydrate the soil, but avoid getting it “sloppy-wet”. You want it to be dark, and hold form in your hands.
Step 2. Add the slow-release nutrients by lightly sifting 20-30% across the top of the mix; mix it in; repeate until all of the slow release nutrients are added and evenly distributed through the soil.
Step 3. Rise and flush the inorganic medium numerous times until the water runs clear.
Step 4. Slowly add and mix in the inorganic medium into the substrate; thoroughly mix it throughout as you add it
Step 5. Add additional water if required to rehydrate the soil.
Step 6. Prepare the pot and fill the bottom 1” with a layer of stones, styrofoam peanuts, or other large-sized inorganic material into the bottom of the pot. This will prevent the dirt at the bottom of the pot from sitting in water after you water.
Step 7. Pot plant with the new soil. Fill in bottom later with soil, add plant, fill in around plant, shake plant and sift new substrate around the roots to evenly distribute it. At the end, you want the soil to be about 1/2″ down from the edge of the pot — this will give you room for water and it will sink down over time as the medium settles.
Step 8. Water the crap out of your plant. Take it to the shower (or sink if possible) and thoroughly wet all the dirt. Add more potting mix if you need to. Let the water run through the soil 2 or 3 times and then turn off water and let drip dry.
Step 9. Put plant in drip tray, place near a window and and repeat watering, just like you did in the previous step, next week (or when soil approaches dryness).
That pretty much covers my top secret, most amazing, spectacular, flawless potting mix. If you have questions, you can send me a message via Facebook from the Here But Not page.