Your own potting mix in Self watering Terracotta pots!

Jul 17, 2012 | Garden How-Tos, Vegetable Gardening

Its a lovely on-going summer here in Irvine in Southern California. Some of our containers had to be replaced, so we got down to work! We wanted to try out the newer self watering containers which claim to conserve upto 80% of the water needed for containers (which is quite true as you will see). Also, this time we wanted to have complete control over what goes into the potting mix. Its also way cheaper to create your own potting mix than use a ready made one like Miracle Grow.

So here’s all that you will need for this project::

1. Containers – Self watering terracotta containers are great – we got the Plant Spa brand. It looks great and seems to be working great as well:

2. Sphagnum peat moss OR Coco bricks – We got Miracle grow sphagnum peat moss
3. Compost, preferably organic compost – We got the Kellogg Enrich brand
3. Perlite – We got the Thermo-Rock brand
4. Vermiculite – We got the Thermo-Rock brand

5. An all purpose organic fertlizer – We got Espoma’s Garden tone
6. Epsom Salt – Any brand will do
7. Garden lime (derived from Dolomite) – if you are using coconut peat, you don’t need this – We got Espoma Garden Lime
8. If you are starting transplants, get some slow release fertilizer like Osmocote  

9. Protective gloves and mask – You will be working in a dusty environment!

19. A tarp. This avoids wasting soil and allows easy cleanup.

Luckily, we found we could buy everything at our local Home Depot and that’s a lot of convenience. If you prefer to shop on-line, you can find everything on Amazon. For your convenience, direct links to some great products are provided above.
The first step is to wear your protective gloves, eye wear and mask. I cannot stress how important it is to use protective wear when doing any home improvement work/yard work. I once made the mistake of using an oscillating tool without ear muffs and it had a very bad effect on my ears after that. So please be careful even if you think you can handle everything without it.
Here’s how the containers look like. We got the 18” ones for growing vegetables and 15” ones for the flowers.It has a big reservoir at the bottom which can provide water to the plants for up to 2 weeks. If you want to save money on the peat moss, Lowes has a cheaper variety – you get 1 cu ft more for the same price as MG at Home Depot.
To create the potting mix, we will use Sphagnum peat moss. Note that you can use coco bricks as an alternative, which expands into coco peat. Coco bricks are not yet available in our area so I used sphagnum peat moss. Here’s the recipe for the potting mix. I used a 5 gallon bucket to measure the parts (You can use your own bucket, bags or drums to measure as long as you are using the same container size for each measurement).

1 bucket sphagnum peat moss (OR coco peat)
1 bucket compost
1/2 bucket perlite
1/2 bucket vermiculite
2 cups all purpose organic fertilizer
1 cup Garden lime
1 cup Epsom Salt


1. Lay a tarp on the ground. The tarp really helps to collect all the mix together without wasting much. Add in all the ingredients and mix thoroughly. Once you “think” its mixed, use a rake and lay it as a flat layer and mix again. You need to make sure everything is thoroughly and evenly mixed to avoid any problems.
2. Now start filling your container.If its not a self watering container, make sure it has drainage holes before you add the mix. The bottom 3 inches of the mix must be firmly pressed down and watered. This is a very important step in order to ensure proper drainage. Keep watering as you add the remainder of the mix towards the top.
3. If you are planting well developed plants, form a ring at around 2 inches from the top and add some Oscmocote or other slow release fertilizer. It will help fertilize your plant for up to 3 months.

That’s it!  Enjoy your new containers and watch your plants thrive.


1. Watering the potting mix as you are preparing it reduces the dust from the perlite/vermiculite and allows easy mixing.
2. If you feel comfortable, you can substitute composted steer manure for organic compost. It will save you some money. I would avoid steer or chicken manure for containers in which I am growing vegetables as its easy for unwanted things to get(insecticides, antibiotics)  into the food chain from manures. No one knows what the cattle grazed on and he/she may well have grazed on grass treated by a banned insecticide. Its better to avoid the risk and use a non-manure source (compost).
3. You can skip the Garden Lime if you are using Coco Peat. Coco peat has neutral PH. Sphagnum Peat moss is acidic, hence lime needs to be added to neutralize the mix.
4. If you do not wish to create your own potting mix, you can use a ready made mix. The best ones available in the market are Supersoil potting soil (brown bag) and EarthGro Potting Soil (White bag). Technically, potting soils and mixes are different but vendors use this term interchangeably. Potting mix is a soil-less mix of peat, perlite, vermiculite and compost. Potting soil may contain other ingredients (dirt). Potting mixes are always a better choice than potting soils.
Have a great summer! I will be back with some summer veggies growing in our California garden!


  1. ET2012

    I like the detailed recipe. Thank you very much for the valuable information. I like how the self watering pots save water. Its only self watering pots for me now. Did you get all the sizes at home depot?

  2. California Gardening

    Glad you liked it. Yes we got all the sizes 15'' and 18'' at Home Depot


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