DIY Seed Raising Mix – Save Money and Grow Healthy Plants

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diy seed raising mix
DIY seed raising mix

Spring is fast upon us, and if you want to get a head start growing vegetables, now is a good time to start germinating seeds either indoors or somewhere where it’s warm.

To raise seeds successfully, you need a good seed raising mix.

While you can buy commercial seed raising mix it can be either expensive or poor quality.

Raising seeds can be tricky enough without hindering the effort with a poor quality mix.

Which is why it’s good to make your own.

A good seed raising mix needs to be free draining but also hold moisture.

It also needs to be fairly fine without stones or large particles like bark to interfere with seed germination.

Making your own seed raising mix is quick and easy and relatively inexpensive, especially if you’re using homemade compost.

The four main ingredients in the seed raising mix are:

  • compost
  • course sand or vermiculite; and
  • coconut coir
  • cow poo/worm castings

The cow poo isn’t essential as all the nutrients a seed needs for germination is contained within itself.

However, once they start growing, your seedlings will need extra nutrients. You can either use manure or feed your seedlings regularly with an organic fertiliser.

On the other hand, if you do have a worm farm, by all means, throw in a handful of worm castings when making your mix!

DIY seed raising mix – the ingredients


If you don’t have your own compost, commercial compost will do just fine. There are benefits to using commercial compost over home-brewed.

Homemade compost may contain seeds of either vegetable or weeds that compete with the seeds you’re trying to grow. You may have trouble identifying which is the seedling you’re growing and which is the weed.

Homemade compost isn’t sterile. It can contain bacteria and fungus that can dampen off (kill) your seedlings.

On the upside, this can help weed out the weak seedlings, ensuring that you’re growing only the strongest plants. This is particularly important if you plan on collecting and storing the seeds for future years.

And of course, homemade compost is cheaper.

The compost needs to be sieved to remove large particles. A garden sieve can be purchased cheaply from a garden store or you can make your own like this one or this one.


Coconut coir is the natural fibre extracted from the husk of a coconut.

It is light, retains moisture and is bacteria and fungus free, making it perfect for seed raising.

Coir can be purchased in a block from a hardware/garden store. A $2 block will make you a lot of seed raising mix.

To use, soak the block in the required amount of water until it expands. Use a bucket with a lid to store the extra coir or dig some into the garden.


While the coir retains moisture, the sand or vermiculite lightens the mix giving it drainage and aeration, aiding root development.

Course sand is cheaper than vermiculite (although neither is particularly expensive). Vermiculite is a natural volcanic material. Unlike sand, it is light and retains moisture and minerals.

Worm Castings

Seeds do not need food to sprout. However, once your seedlings start growing, they’ll need some extra food.

Avoid the need to replant in another mix – and therefore risk transplant stress – by adding a small amount of worm castings (ideally) or cow or sheep manure to your mix.


2 parts compost

2 parts coconut coir

1 part vermiculite

1/2 part castings

Raising your own seeds cheaper than buying seedlings from the nursery. And if you collect your seeds, growing is free and over time you’ll be growing vegetables that are adapted to your backyard’s particular micro-climate.

To get the best start and protect biodiversity, look for heirloom seeds like these or these.

Seeds, like babies, need extra TLC in order to grow strong and healthy. Give them the best start with your own DIY seed raising mix.

diy seed raising mix


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  1. I part sterilize/pasteurize my compost using passive heat from the oven.
    I’ll place half an inch of compost in a baking tray (an old one only used for this of course)
    and thoroughly water it. Cover with foil, and as soon as whatever I was cooking is taken out of the oven this goes in and I drop the temperature to around 220F.
    After 15 mins I’ll turn the oven off but leave the compost in there to slowly cool.
    Most times the oven doesn’t click back on during that 15 min period so not much extra electricity to get it done.

  2. Awesome, currently in COVID 19 lock-down means I can not purchase seed raising mix, but as an organic gardener I do have everything else to make this – Thank goodness. Thanks Melissa for your blog. And thanks to Gerry on how to sterilise the compost.