Starting your seeds off in the right soil is one of the most important steps to growing healthy, thriving plants. The debate between making your own seed starting mix or purchasing seed starting soil is an important one. 2 years ago we made a video testing and exploring 4 different seed starting mixes. We shared the results of our experiments and crowned a clear winner!
When it comes to seed starting, the soil you use can make or break the health and success of your seedlings. While it’s tempting to grab a bag of store bought seed starting soil, making your own mix offers numerous advantages that are hard to ignore.
Let’s break down why homemade seed starting mixes are better:
Customizable
When you make your own seed starting mix, you have full control over the ingredients. You can tweak the blend to ensure it provides the perfect balance of moisture retention and aeration for your seeds. Store bought mixes, on the other hand, are mass produced and designed as one size fits all solution, which may not be ideal for your specific plants or growing conditions.
Cost effective
Pre-packaged seed starting mixes can get expensive, especially if you’re starting a lot of seeds. By purchasing bulk ingredients and making your own mix, you can save a significant amount of money in the long run. Plus, you can reuse or repurpose some of the ingredients for other gardening needs.
Quality control
Store-bought mixes sometimes contain low-quality or non-organic ingredients that may not be ideal for your garden. By making your own, you know exactly what’s going into the soil, ensuring that your seedlings are getting the best possible start.
Eco-friendly
Many pre-packaged seed starting soils rely heavily on peat moss, which is not a sustainable resource. By creating your own mix, you can opt for more sustainable and environmentally friendly ingredients, such as coco coir, which is a byproduct of coconut processing.
Results
Homemade seed starting mixes can be tailored to optimize the growth of your seedlings. This means healthier root systems, stronger stems, and, ultimately, more productive plants.
By making your own seed starting mix, not only do you save money or avoid synthetic ingredients. It’s also about giving your plants the best possible foundation for growth.
Here are some of the key benefits:
- Improved aeration: Healthy roots need good airflow, and homemade mixes allow you to include ingredients like perlite or vermiculite to keep the soil loose and well aerated.
- Moisture retention: A good seed starting mix holds just the right amount of water without becoming soggy. Ingredients like coco coir and worm castings help retain moisture while preventing water logging.
- Nutrient control: Seedlings don’t need a lot of nutrients early on, so starting with a low nutrient mix can prevent problems like nutrient burn. As they grow, you can gradually introduce more nutrients.
- Fewer pests and diseases: When you create your own mix using clean ingredients, you reduce the risk of introducing harmful pathogens or pests that can be present in some store bought soils.
Testing 4 seed starting mixes
To figure out which mix works best, we tested four different seed starting blends to compare their performance.
Here’s a breakdown of each mix
Mix #1: 1 Part worm castings + 2 parts coco coir
This simple blend focuses on providing a clean, nutrient light environment for seeds. Worm castings offer mild, organic nutrients and beneficial microbes, while coco coir ensures excellent moisture retention and aeration.
Mix #2: 1 part coco coir + 2 parts worm castings with fish bone meal, blood meal, gypsum, rock dust, and perlite
This nutrient rich mix includes a variety of amendments to provide a wide range of minerals and organic matter.
Mix #3: Pro mix blend (perlite, sphagnum peat moss, limestone, mycorrhizae, compost, gypsum, organic fertilizer, and coco coir)
A store bought premium blend with a mix of both natural and synthetic components designed for general seed starting use.
Mix #4: 1 part regular potting soil + 1 part worm castings
A straightforward mix combining basic potting soil with nutrient rich worm castings.
Results of the experiment
After testing these mixes with various seeds, we found some surprising and not so surprising results. Here’s what we discovered:
Mix #2 and Mix #3 (High nutrient mixes):
While these mixes were packed with nutrients, they were actually too “hot” for young seedlings. Seeds germinated just fine, but we noticed signs of nutrient burn (yellowing leaves and stunted growth) shortly after sprouting. Seedlings don’t need a lot of nutrients early on, so these mixes overwhelmed them instead of supporting their growth.
Mix #4 (potting soil + worm castings):
This mix worked decently well, but regular potting soil tends to be too dense for seed starting. The heavier texture made it harder for roots to spread and for water to drain properly. As a result, some seedlings struggled with damping off (a common fungal disease).
Mix #1 (worm castings + coco coir):
This blend was the clear winner! The coco coir provided an excellent balance of moisture retention and aeration, while the worm castings offered enough nutrients to sustain the seedlings without overwhelming them. The seeds germinated quickly, and the seedlings grew strong, healthy roots and sturdy stems.
Why mix #1 is the best seed starting mix
Mix #1 — a simple combination of 1 part worm castings and 2 parts coco coir — stood out as the best option for several reasons:
Perfect for seed germination
Seeds don’t need a lot of nutrients to germinate because they rely on the energy stored within the seed itself. This mix provides a low-nutrient environment that encourages healthy root development without risking nutrient burn.
Great moisture retention and aeration
Coco coir holds moisture well while also draining excess water, keeping the soil light and fluffy. This prevents issues like waterlogged roots or fungal diseases.
Beneficial microbes and nutrients
Worm castings are rich in beneficial microbes that promote healthy soil life, as well as small amounts of natural nutrients that provide a gentle boost to seedlings as they grow.
Affordable and sustainable
Both coco coir and worm castings are affordable, sustainable ingredients. Coco coir is a renewable resource, and worm castings can even be made at home if you’re into vermicomposting.
Versatility
This mix works well for a wide variety of seeds, from flowers to vegetables. Once your seedlings are ready to be transplanted, you can simply move them into a more nutrient rich soil mix or directly into your garden soil.
How to make your own seed starting mix
Making Mix #1 is incredibly simple and requires just two ingredients:
- 1 Part worm castings
- 2 Parts coco coir
Here’s how to make it:
- Start by hydrating your coco coir if it’s in a compressed brick form. Follow the manufacturer’s instructions to add water until it expands fully.
- Mix the hydrated coco coir with worm castings in a 2:1 ratio. Use your hands or a trowel to combine the ingredients thoroughly.
- Check the texture of the mix, it should feel light and fluffy, and it should hold its shape when squeezed but crumble easily when poked.
- Your seed starting mix is ready to use! Fill your seed trays or pots with the mix, plant your seeds, and water lightly.
When it comes to starting seeds, the soil is everything. While store bought seed starting mixes may seem convenient, making your own mix is not only more affordable but also better for your plants and the environment. After testing 4 different mixes, the combination of 1 part worm castings and 2 parts coco coir emerged as the winner, and for good reason! This simple, effective mix provides the perfect environment for seeds to sprout and seedlings to thrive.
Note: We made this video 2 years ago and we have been using the exact same mix for the past years and it’s been a seed starting mix that is affordable, effective and reliable.
Give Mix #1 a try, and you’ll be amazed at the difference it makes in the health and vitality of your seedlings.
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