This DIY seed starting mix is a cost-effective way to provide your spring garden seeds with the ideal environment for germination and early growth, and ensure they develop into healthy, thriving plants.
Starting seeds indoors is a rewarding way to get a head start with plants that will be ready to transplant later this spring in your garden. In order to do this, though, you will need a good quality seed starting medium.
While commercially available seed starter mixes are convenient, creating your own soilless potting mix recipe allows for customization, cost-effectiveness, and peace of mind because you’ll know exactly what goes into your mixture.
Keep reading to learn how easy it is to make a seed starting mix and why it is important. Also, get an additional recipe for a soilless potting mix for seedlings and plants.
Seed starting mix vs potting soil
When comparing a seed starting mix vs potting soil, it’s essential to understand their distinct purposes and compositions.
The best seed starting mix is specifically formulated to provide optimal conditions for germinating seeds and nurturing young seedlings. It typically consists of lightweight, well-draining materials such as peat moss, vermiculite, and perlite.
These materials promote healthy root development and prevent damping-off disease which often affects tiny seedlings.
On the other hand, potting soil is designed for use with transplanted seedlings or mature plants in containers. It often contains a blend of organic matter, such as compost or aged bark, along with perlite or vermiculite for drainage.
Potting soil is more nutrient-rich and dense compared to a seed starter mix, making it too harsh for starting seeds.
DIY seed starting mix
Seed starter mixes offer several advantages over traditional soil-based mixes. They are lightweight, well-draining, and free of weed seeds, pathogens, and pests that can hinder seedling growth.
Also, soilless mixes provide the ideal balance of aeration and moisture retention necessary for healthy root development and seedling establishment.
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Ingredients for a soilless potting mix
This basic seed starting mix recipe is surprisingly simple to make and requires only three ingredients, readily available at garden centers. I’ve also linked to my source online.
You’ll need just three items to make the mix:
Sphagnum peat moss – This is the primary component of the mix, and provides excellent water retention and aeration. Look for high-quality, finely milled sphagnum peat moss to ensure uniformity in texture.
Vermiculite – Vermiculite is a naturally occurring mineral that helps improve soil structure and moisture retention. It also aids in seed germination by maintaining a consistent level of moisture around the seeds.
Perlite – Perlite is soil amendment that creates lightweight, porous particles to improve drainage and aeration in the mix. Perlite helps prevent compaction and promotes healthy root growth.
To make the homemade seed starting mix, you’ll be using equal parts each of each ingredient:
- 1 part sphagnum moss
- 1 part vermiculite
- 1 part perlite
How to prepare the seed starting mix
In a clean container or wheelbarrow, combine one part peat moss with one part of each ingredient. For example, if using a standard measuring cup, you could use one cup of each ingredient for a small batch of seed starting medium.
Thoroughly mix the ingredients together until they are well combined. Break up any clumps of peat moss and be sure there is an even distribution of vermiculite and perlite throughout the mix.
Once mixed, moisten the soilless potting mix with water until it reaches the desired consistency. The mix should be damp but not soggy, with enough moisture to hold together when squeezed but it should not drip water when pressed.
Wetting the seed starting mix before planting seeds helps to settle the mix, ensuring good seed-to-soil contact and improving overall germination rates.
That’s all there is to making this soilless potting mix!
Transfer the seed starting mix to seed trays, pots, or other containers, filling them to the desired level. Gently pat down the mix to remove any air pockets and create a level surface for planting seeds.
Plant your seeds according to the instructions on the seed packet, covering them with a thin layer of the soilless potting mix. I can’t wait to see what color my Lenten rose seedlings turn out to be!
Water gently to ensure good seed-to-soil contact and provide bottom heat if possible to encourage germination.
Be sure to store your left over supplies in a covered container, in a cool, dry place. They keep without going bad and you’ll have plenty to start your seeds next year and beyond.
I often add perlite or vermiculite to my commercial potting soil to help with drainage, so I always have a use for it. Plus, these ingredients can also be used when you take cuttings for propagation.
Enriched potting mix
Once your seeds have grown their first set of true leaves (called cotyledons,) you can plant them in the garden if weather permits. However, if you are planning on replanting seedlings into a larger pot before you move them outdoors, I would recommend that you use the enriched potting mix recipe below.
In this recipe, you use the same ingredients as the basic mix, in different amounts, and you add some compost for extra nutrition.
Here is the enriched soilless potting mix formula:
- 4 parts sphagnum peat moss
- 2 parts compost
- 1 part vermiculite
- 1 part perlite
As before, mix well and wet thoroughly. Repot your seedlings into small pots with the enriched potting mix and continue growing them until it’s time to plant them outside.
Share this DIY seed starting mix recipe on Twitter
If you enjoyed learning how to make a homemade seed starting mix and my soilless potting mix, be sure to share these recipes with a friend. Here is a tweet to get you started:
🌱 Ready to kickstart your garden? Learn how to make the perfect seed starting mix and an enriched soilless potting mix on The Gardening Cook! 💧🌿 #SeedStarting #GardeningTips #DIY #SoillessMix #GreenThumb Share on XOther inexpensive DIY seed starting tools
This seed starting mix recipe is a cost-effect medium to use for starting seeds. Here are a few more inexpensive tools to help you get your seeds started this spring:
- 10 Frugal Seed Starting Pots and Containers – You won’t believe some of the things you can use to start seeds in!
- Cardboard Tube Seed Starting Pots – Make these eco-friendly containers in just minutes.
- Make Your Own Seed Tape – Make a homemade seed tape using toilet paper.
- DIY Newspaper Seed Pots – They are super easy to make!
- Rotisserie Chicken Mini Terrarium – It’s perfect for starting seeds or nurturing cuttings.
Pin these soilless recipes
Would you like a reminder of this post for making a seed starting mix and a soilless potting mix? Just pin this image to one of your gardening boards on Pinterest so that you can easily find it later.
You can also watch our video on YouTube!
Make Your Own Seed Starting Mix
A good quality seed starting mix should be light and airy with good water retention should nurture root development.
Normal potting soil is enriched and too harsh for seeds. Luckily, a soilless mix is easy to prepare.
Materials
- I cup of sphagnum peat moss
- 1 cup of vermiculite
- 1 cup of perlite
- About 1/3 cup of water (should be moist but not dripping wet.)
- Seeds of your choice
Tools
- Bowl
- Heat Mat (optional)
Instructions
- This recipe uses equal parts of each ingredient. I made 3 cups using 1 cup each of peat moss, vermiculite and perlite.
- You can make more, just use equal amounts of each.
- Add enough water to moisten the mix but not have it dripping wet.
- Mix the ingredients well making sure to break up any clumps and incorporate all of the ingredients.
- Place in small seedling trays or a seed tray.
- Add your seeds and place a thin layer of the mixture over the seeds.
- A heat mat under the pots or tray will hasten root development but is not necessary.
Notes
If you want to transplant the seeds into pots before planting outdoors, use an enriched soilless potting mix. Combine these amounts, as directed above.
- 4 parts sphagnum peat moss
- 2 parts compost
- 1 part vermiculite
- 1 part perlite
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