Make Your Own DIY Seedling Mix for Cheap
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It’s cheap and easy to create your own DIY seed starting mix.
When I started the ‘hobby’ of gardening I was in college and broke! I realized quickly that pre-made seed starting mix was outrageously expensive and not in my budget (sigh) AND I was working at a hardware store getting a discount, lol.
Starting a small or large garden can sometimes feel that you’re seeping money to build the beds, fill the pots, buy the supplies or feed the growing garden. But, I’m here to share that you can start your seeds on a budget! I get the most value by making my own seed starting mix and the recipe only calls for 3 simple ingredients that you can store indefinitely. Use what you want, when you want.
Are you ready to save money with my non-complicated organic seed starting mix? Keep reading to grab my fail-proof recipe.
Jump To…
What is Seed Starting Mix?
Is Seed Starting Mix Necessary?
What’s the Difference Between Potting Soil and Seed Starting Mix?
The Seed Sage’s Best DIY Seed Starting Formula
How to Make the Best Potting Soil Mix for ‘Potting Up’ or Moving Seedlings to Bigger Pots
Common Questions about Seed Starting Mix
Where to Buy Seed Starting Mix
You can grow bountiful, beautiful crops by mixing your own organic seedling mix
What is Seed Starting Mix?
When it comes to starting your own seeds you need to create or buy a mix that is lighter and finer so your baby seedlings can easily form their roots without compression. Seed-starting mix is a soil-less medium for starting organic seedlings. There is one major benefit to an organic diy seedling mix- COST!
Personally, when I have purchased bags of seedling mix in the past the cost vs the amount is high. One bag never covers the amount of seedling trays I need to get started. Once I started making my own soil-less medium I quickly realized how much money I could save. For instance, an 8 qt bag can cost up to $7-8 dollars and will barely cover the cost of filling a 32 cell seed tray.
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I tend to be a bit uptight when it comes to starting my seedlings because I am growing for my client garden installs in Austin, Texas most of the year. I want full control over what ingredients are going into my seedling mix recipes. When purchasing pre-made bags of seed-starting mix you could be introducing odd chemicals to your germinating seeds.
Seedlings are self-sufficient and do not require extra nutrients when germinating much like a newborn does not require milk (only colostrum) in the first few days of life. And just as you want a baby to figure out tummy-time, sitting up, crawling or walking, we want to give our seedlings a chance to grow strong on their own terms. DIY seedling mixtures will ensure you know what products are going into your medium and you will save money. A win-win!
Is Seed starting Mix Necessary?
I feel that seed starting mixtures are necessary but I’m aware some gardeners throw caution to the wind and use whatever potting mix for germination they have on hand. My sister is known for using potting mix to start seeds and approaches gardening with a much different mindset. She will use whatever soil or dirt she has on hand to start her seedlings and does have some success. I want to remind you that we all have different approaches; I’m simply sharing my experience and seedling success secrets for a bountiful harvest.
Personally, I try to keep my environment as sterile as possible to avoid unnecessary diseases, fungus and pests. Since I coach my clients and sometimes grow their initial seedling starts for them, I don’t want to risk spreading illness to their garden. This article is for those of you who want to grow the healthiest most robust seedlings and are curious about the optimal mix. Just remember I speak from my own journey and there is nothing wrong with you deciding to purchase your own seed-starting mix. I am a strong advocate for experimenting in the garden while staying present and stress-free.
What’s the Difference Between Potting Soil and Seed Starting Mix?
As stated earlier, the seed-starting mix is a soil-less medium. It is lighter than your traditional potting soil mixes. Potting soil is heavier and composed of compost, manure, earth soil as well as peat moss and some vermiculite. I have found that most bagged potting soil are possibly…
Infused with different amounts of fertilizer which can be of detriment to your growing seedlings if they are sensitive. Burning can occur and your seedlings might not get started
Hold too much clay which can create too much moisture
Have large chunks of organic debris such as bark which hinders the seed from making contact with the growing medium
Might contain fungi or bacteria that will cause issues such as damping off which kill the growing seedling
Worm castings are an excellent addition to your homemade seed starting ‘soil’.
The Seed Sage’s Best DIY Seed Starting Formula
What is The benefit of a homemade seed starting mix? A clean, worry free start to growing your garden. Jennifer’s 4 ingredient seed starting formula provides the right amount of fluff, moisture and drainage for your growing seedlings.
COCO COIR (OR SPHAGNUM PEAT MOSS)- While sphagnum peat moss is an excellent, sterile, moisture retaining ingredient, I feel it has too much acidity for starting my seedlings. This is not to say I wouldn’t use it in a pinch, but my preferred medium is coco coir. Coco coir is very similar to peat moss in all characteristics but is made from the fiber of coconut shells.
PERLITE- A naturally occurring mineral that is white and light weight and looks like broken up styrofoam. This lightweight volcanic glass provides aeration and drainage. STARTING SEEDS IN PERLITE…
VERMICULITE- Also a naturally occurring material, vermiculite is an earth toned flakey micha-like material that helps prevent overwatering and root rot. Vermiculite is added in the garden to improve poor quality, heavy, wet soil and is a key ingredient in a good seed starting mixture.
WORM CASTINGS (optional)- Worm casting seed starter…This is a personal preference and is not necessary. You might be asking if adding worm casting will cause burning of the seedlings since it is an organic soil amendment, but I’m here to share that it is quite safe and even beneficial to your germinating seedlings. For a few years now I have used VermisTerra’s Premium Worm Castings to add to my seedling mix. The castings provide beneficial microbes and bacteria to help improve structure to the growing medium and introduce an increase of oxygen which creates more space for the roots to form. If you are interested in reading more about the benefits of worms in your garden read our article here!
BASIC DIY SEEDLING MIX RECIPE:
1 Part coco coir (or peat moss) ie- 16 oz bag
1 Part perlite
1 Part vermiculite
1 HANDFUL* or approx 1 cup (if using 16 oz bags of above ingredients) worm castings (this is what I have used for years)
*You cannot add TOO much worm castings so just think of the recipe as a 1:4 soil to casting ratio depending on how much you need to make.
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How to Make the Best Potting Mix for ‘Potting Up’ or Moving Seedlings to Bigger Pots
If you are planning on replanting seedlings into a larger vessel, aka ‘potting up’, and not moving seedlings outside yet I would recommend starting with the enriched potting mix recipe. Once transferred to their new home you can add an amendment like liquid seaweed to your mixture. If you are transplanting germinated seeds to soil, I will soon have an article about how I amend raised beds each season to prepare for transplanting and how to properly ‘harden off’ your seedlings.
What is potting up? Potting up is when I take my small seedling and move it to a larger container to allow it to develop more before transplanting. But why would I do this? The weather might not be ideal for transplanting or the plant has outgrown its container.
ENRICHED POTTING-UP POTTING MIX
4 PT coco coir (or peat moss)
2 PT organic compost
1 PT perlite
1 PT vermiculite
DIY Seed Starting Mix
Ingredients
Instructions
- Mix equal parts of coco coir, perlite and vermiculite.
- Add handful of worm castings, if using
- Use hands or large spoon or shovel to mix until mediums are combined.
- Wet only until you can form a loose ball (water should not be dripping from compact mixture)
- Fill pots and begin to seed!
- Gently spray or water the surface of soil-less mixture to set seeds.
Common Questions About Seed Starting Mix
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There is controversy in the gardening community about whether or not to sterilize your mix. Up until recently I would sterilize my premade bag mixes but have realized that the harmful fungi actually caused my seedling to dampen off. I was causing more harm than good. Heating your soil or seed starting mix will change the structural nature of soil and will make it less suitable for growing plants.
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No! It does not. If the mix has been dampened let dry and place in an air tight container. You can open and use only what you need.
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As long as you don’t have issue with pest or disease with you first batch- go for it!
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As long as your soil is healthy and free of disease, fungus and pests you can creatively use your old potting soil.
Use the old potting soil to fill the bottom of new containers you are planting. This can save you money instead of filling whole pots with a newly purchased bag.
Mix into existing soil in the garden or yard.
Mix into your compost (my favorite options).
Where to Buy Seed Starting Mix
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Burpee 8-qt Vermiculite | Hoffman 8qt Perlite | xGarden 8-qt Premium Perlite | Burpee 8-qt Garden Coir | Perfect Plants 8-qt Organic Garden Coir | Burpee 16-qt Coco Coir Block | Gardeners Supply Company Seed Starter Kit | Bootstrap Farmers 32 Cell Seed Starting Tray | Epsoma 8-qt Seed Starting Mix | VermisTerra Worm Castings
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