Make your own sterilized seed-starting mix
Creating your own sterilized seed-raising mix ensures the cleanliness and quality of your growing medium and is very cost-effective compared to buying pre-made mixes. I’ve been experimenting with making my own seed-raising mix for a while now and have recently started sterilizing it to save myself some issues further down the track. The biggest issue I had was sifting my own compost and using that, but it almost always had too many weed seeds in it. This is what I have started doing instead.
Cost-Saving Sterilized Seed-Raising Mix Recipe
Ingredients:
- Coconut Coir: 1 part (an eco-friendly alternative to peat moss)
- Perlite 1/2 part
- Coarse Sand: 1/2 part
- Compost (optional): 2 parts
Optional ingredients
Store bought fertilizers occasionally have added elements to give plants a little growth burst once they start maturing. You don’t have to do this, especially if the intention is to plant your seedlings as soon as they are big enough to transplant. That’s not always possible in a busy life, so knowing a little about your own soil and your plants specific needs could be useful when preparing some mixtures. This would be a more appropriate cost if your seedlings were slow growing.
- Garden Lime (To raise pH)
- Elemental sulphur (To lower pH)
- General Fertilizer
A comparison of cost
- compost free 10 – 10 litres
- coconut coir $6 for – 5 litres – 3.00
- course sand $5.30 for 10L – 2.5 1.33
- Perlite $15.60 – 2.5 – 3.90
- = $8.23 / 20 L or $4.11/10L
- Seed starter mix $7.00 – $10.00 / 10L
Depending on how much of your own sterilized compost you add into mix the savings will differ, but you can expect to pay at least half the cost of a store bought seed-starting mix. You just need to consider whether it is worth your time for the amount of seeds you would like to start yourelf. In terms of equipment I use an old toddler clam shell swimming pool to mix up my ingredients and I have a sieve for taking out particles that are too large to suit seed-raising. The sieve I purchased for about $25.00 NZD.
DIY Seed-raising mix
Instructions:
- Gather Your Materials: You’ll need a large container or wheelbarrow for mixing, a large container suitable for the oven or microwave for sterilization, and a pH testing kit (optional).
- Measure the Ingredients: Use equal parts of coconut coir, perlite or vermiculite, and coarse sand. Adjust the recipe to make more or less, depending on your needs.
- Blend the Ingredients: Combine coconut coir, perlite/vermiculite, and coarse sand in your mixing container. Thoroughly mix them to create a well-balanced base mix.
- Optional Compost: If you have compost available and want to introduce organic matter, add it to the mix. Ensure it’s evenly distributed among the other ingredients. The only reason I would do this however is to add bulk since the point of compost is the microbial life it offers your garden.
- Check and Adjust pH (Optional): Test the pH of your mix; the ideal range is slightly acidic to neutral (around 5.5 to 7). Adjust the pH using garden lime to raise it or sulfur to lower it. Mix thoroughly after any adjustments.
- Sterilize the Mix: Sterilization is essential to eliminate pathogens, weed seeds, and undesirable organisms. There are two common methods:
- Oven Method: Spread the mix on a baking sheet and heat it in the oven at 180-200°F (82-93°C) for approximately 30 minutes. Monitor closely to prevent overheating.
- Microwave Method: Place the mix in a microwave-safe container and heat it in short intervals (1-2 minutes) until it reaches around 180°F (82°C). Stir between intervals for even heating.
- If you are just making a small batch you can just add boiling water to the mix then let it drain and dry.
- Allow Cooling: Let the mix cool completely before using it for seed starting. Sterilization may kill beneficial microorganisms, so consider inoculating it with beneficial mycorrhizal fungi if desired. If your plants are to remain in their starter pots then you can use organic fertiliser tea to add microbes and nutrients into the soil after your plants are established.
By making your own sterilized seed-raising mix with cost-effective ingredients like coconut coir, you not only save money but also contribute to sustainable gardening practices. Fill your seed trays, pots, or containers with this mix, sow your seeds, and provide the right moisture and light conditions for germination. Don’t forget to label your containers with the seed type and planting date for easy tracking and management.
Another way to reduce the number of rogue seeds from popping up their hungry little heads amongst your intended seedlings is to produce your compost using hot composting. This process raises the temperature to a rate that will kill weed seeds.
