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How to Create Organic Seed Starting Mix

Eco-friendly, organic gardening is beneficial for you and your soil. But, it can be hard to decipher which products are truly organic.

Did you know you can take the guesswork out of it and create your own organic seed starting mix?

In this post, I’ll go over the ingredients and step-by-step process of making an organic seed starting mix. Keep reading to discover the ins and outs of this DIY project!

A starter tray with seed starting mix and seeds.

Why Create Organic Seed Starting Mix

Control Ingredients

The best reason for creating your own seed starting mix is to have control over the ingredients.

Many gardening products are labeled as organic, with or without certification. This leaves you reading the fine print to ensure you get a truly organic product.

By purchasing individual ingredients, you’ll have full control and knowledge of everything going into your mix.

By having control of ingredients, you can also tailor your mix to what your seedlings and soil need. This allows you to adjust the recipe as necessary for more drainage or better water retention.

Ingredients to make growing medium, such as organic seed starting mix.

Save Money

One of my favorite perks of any DIY project – save money!

It may feel like you’re spending more money upfront for individual ingredients. But, in the long run, you can create a lot more mix than what’s in a standard pre-made bag.

You’ll also have all the supplies at your disposal if you need more mix than you initially threw together. That means no running back and forth to the garden center or nursery.

Organic Seed Starting Mix Ingredients

Let’s talk about the top three organic seed starting mix ingredients: coconut coir, perlite, and vermiculite.

All the recipes you find online will be a variation of these products. You may see some additional elements added in. But your mix must have most of these main ingredients.

Coconut Coir

Person with a handful of coconut coir, a main ingredient of organic seed starting mix.

Coconut coir is the main ingredient for DIY organic seed starting mix. It comes from the layer of fibers between the husk and meat of a coconut.

It’s extremely lightweight, which is perfect for adding drainage and airflow to your seed starting mix. Coconut coir also helps seedlings easily form healthy roots.

In contrast to peat moss, coconut coir is sustainable and good for the environment. Many gardeners choose it over peat moss because of the amount of carbon dioxide released when peat moss is harvested.

Coconut coir usually comes in dehydrated bricks, which must be wetted to expand. It’s also cost-friendly, which is great because it will make up the bulk of your seed starting mix.


Person with handful of white perlite.

Now, let’s talk about perlite. You may be familiar with the tiny white beads found in many seed starting mixes.

Perlite is a natural mineral that is mined from volcanic glass. But, perlite doesn’t appear as tiny white beads at first. When extreme heat is applied to the dark grey mineral, it expands into the white substance you see.

Because heat is applied to the mineral, it’s sterile and non-toxic.

So, what is it good for?

Perlite simultaneously helps with water retention and drainage. The porosity of perlite helps retain enough moisture to keep seedlings hydrated. And the white beads help break up the mix to add drainage and airflow.


Person with handful of vermiculite.

Vermiculite is another beneficial mineral to add to your organic seed starting mix. It’s similar to perlite in its uses, but vermiculite is mined from the ground instead of volcanic glass. It’s also light brown in color compared to bright white perlite.

Vermiculite is treated with heat before being sold as a garden additive. So, it’s non-toxic. You won’t have to worry about accidentally introducing diseases to your soil.

Like perlite, vermiculite helps with water retention and drainage. But vermiculite is highly absorbent, so it’s better at holding water than perlite. This is good for reducing the need to constantly water seedlings.

Optional Ingredients

Person with handful of worm castings.

Besides the big three, there are a few optional ingredients you can add to your organic seed starting mix.


Compost can be made of decomposed food products, manure, or recycled paper. It’s affordable and improves the health of your soil. Because it doesn’t contain a surplus of added nutrients, it’s safe to use with seedlings in moderation.

Worm Castings

Worm castings also improve the health of the soil. This end product of earthworm digestion creates aeration and water retention in the soil. These are both great benefits for seedlings!

Bone Meal

Bone meal is created from ground animal bone matter, which creates an organic powder. When added to soil, it introduces a healthy source of calcium and phosphorus into the soil. It should be used sparingly in seedlings, but it can give them a boost in growth.

How to Create Organic Seed Starting Mix

Now that you’ve sorted out your ingredients let’s talk about how to create an organic seed starting mix.

Prepare Your Space

A plastic bucket of seed growing mix ingredients.

The first thing you’ll want to do is prepare your workspace to set yourself up for success.

Clear a workbench or potting table to create your mix.

Set out each of the ingredients you plan on using. This will make it convenient to grab whatever you need next without going on a hunt.

You’ll also need the following supplies:

Measure Out and Sift Ingredients

Person adding vermiculite to seed starting mix.

Now, it’s time to measure out your ingredients. I recommend using the following recipe for a simple organic seed starting mix:

  • Two parts coconut coir
  • One part vermiculite
  • One part perlite

Use the same measuring cup for all ingredients to get a consistent measurement. Place each measured ingredient into the large bowl.

Note: coconut coir comes dehydrated, so you’ll need to moisten it before mixing it in.

If you use compost, make sure to sift it out before mixing it in with everything else. Use a standard soil sifter, or you can even get creative and use a metal grate or chicken wire. Removing any large chunks of bark or soil will help prevent air pockets and hindered root formation.

Mix Ingredients

Person hand-mixing seed starting mix.

If you haven’t already, put on your gloves and get to mixing! Mix by hand until all ingredients are thoroughly combined.

Wet the Mix

Once the mix is combined, you’ll begin to add water slowly.

Wetting the mix will be beneficial once you add it to your seed starting trays. There will be fewer chances of air pockets. And you won’t have to worry about washing away small seedlings with water droplets.

The goal is to get the mix to the same consistency as peanut butter. Take and handful and stick it to the side of the bowl. It shouldn’t slide off (too wet) or fall apart (too dry).

Small pots of organic seed starting mix.

Storing Organic Seed Starting Mix

So, you made too much organic seed starting mix? No problem! You can easily store the mix for later use.

Allow the mix to dry out completely. This will prevent mold and mildew from forming on the mix.

Once dry, you can store the mix in an airtight container or lidded bowl. When you’re ready to start more seeds, just add water to your mix as you did originally.

Frequently Asked Questions

1. Can I purchase an organic seed starting mix pre-made?

Yes! If creating your own mix sounds like too much trouble, I understand. Life is busy, and extra time can be hard to come by.

There are several great pre-made organic seed starting mixes out there. Try out Hoss’ Premium Seed Starting Mix.

Hoss premium seed starting mix.

For more pre-made choices, here are my favorite seed starting mixes.

2. Is seed starting mix the same as potting soil?

Seed starting mix and potting soil are quite different.

Seed starting mix is soil-free and uses only natural, lightweight ingredients. This helps seedlings with healthy root formation, drainage, and moisture retention. It also doesn’t typically include added nutrients, which can overwhelm and stunt small seedlings.

Potting mix, on the other hand, does contain soil and added nutrients. It should be used for mature plants no longer in the small seedling stage.

For more information on the difference between the two, read our blog post, Seed Starting Mix vs Potting Soil.

Wrapping Up Organic Seed Starting Mix

A pepper seed on seed starting mix.

Are you ready to create your own organic seed starting mix? It’s easy and can save you money in the long run. Not to mention, you’ll know exactly what’s going into your garden!

Don’t let growing season sneak up on you! Visit our Seed Starting Page to learn all there is to know about starting your favorite vegetables and flowers.