Seed Starting Soil from the store (or online) can be really expensive, especially if you are starting a lot of plants from seed. Learn how to make your own homemade seed starting soil mix in order to save money and have confidence in good-quality ingredients.
Why I Am Making Homemade Seed Starting Soil Mix
For many of my early plants, I can just put those little seedlings in their peat pellets right into the garden. However, when I start both pepper and tomato seeds inside, they usually have to be upgraded to pots for a few weeks before it’s time to plant them in the garden.
I always use a seed starting soil mix when I transfer my peppers and tomatoes to bigger pots. In the past, I wince at the price of seed starting mixes from stores or online (seriously, check out the price on this small bag of organic seed starting soil mix!), but since I only needed one or two bags of it each year, I just shrugged and put it in the gardening budget as a necessity.
This year, however, I am increasing the amount of plants that I am starting from seed. First, my friend asked me to start peppers and tomatoes for him. That doubles the amount of seed starting soil I need for the year. And yeah, I would have my friend share on that price, but it’s still crazy expensive.
Second, I’m starting flowers from seed for the first time ever (besides the edible flowers and zinnias that I always plant in my vegetable garden). Suddenly, I was looking at purchasing at least $200.00 worth of seed starting soil mix. Yikes. No thanks.
After cringing a lot at that crazy price, I decided that this year I am making my own homemade seed starting mix.
1. My Own Seed Starting Soil Will Save Me Money.
Instead of spending about $200.00 on store-bought organic seed starting soil, I ran some numbers and realized that I could get the materials I needed to make homemade seed starting soil for about $60.00.
And 60 bucks gave me WAY more seed starting soil mix ingredients than I need for this year. In fact, I‘ll probably have enough seed starting soil ingredients to last me about 3 years! At least. There’s quite a bit leftover so far!
2. Homemade Potting Soil Ingredients Has Multiple Purposes.
One thing I realized with my homemade seed starting soil ingredients is that I can use those ingredients for more than just starting seeds. For example, I’m going to be expanding my gardening skills into the world of container gardening. The same ingredients used for seed starting is used in homemade potting soil for containers. It’s just different ratios. So I have everything I need for good quality container gardening now! Huzzah!
I can also use these soil mix ingredients to help in my raised beds. For example, if my soil is too soggy, I can add some of the vermiculite or peat moss to the raised beds to improve drainage. Plus, all my new flower beds are going to need some loving in the form of good quality soil!
3. Homemade Organic Seed Starting Soil Means You Know The Ingredients.
I try really hard not to be one of “those people” who are paranoid that all big companies are evil and trying to poison me. That being said, I still would prefer to make my own supplies than learn about yet another common everyday item that turns out has something bad in it. (I mean, I just learned that some popular tea bags are putting plastic particles in my body!).
Most of the seed starting soil mixes that I find online are from big gardening companies whom I don’t even trust for purchasing seeds. I know their seeds aren’t the best quality (here’s my info on finding good-quality organic seed companies), so why should I trust their seed starting soil?!?
So yeah, it’s a lot nicer to make my own homemade seed starting soil mix and that way I know what ingredients are in it. I was very careful that the ingredients I used came from good sources. Make sure you talk to your garden store workers if you can’t find the labels on the ingredient packages.
My Seed Starting Soil Mix: The Ingredients
I spent a bajillion hours researching seed starting soil and looking at tons of different soil recipes and focused on narrowing it down to something that makes sense and won’t break the bank.
A good seed starting soil mix must be:
- Not too high in nutrients (that can harm precious seedlings)
- It must hold onto moisture without becoming too soggy (which can drown your seedlings or product rot/disease)
- Light and fluffy soil that allows plenty of air around the roots (compact soil suffocates seeds/seedlings)
Do NOT just use normal potting soil for seed starting!!!!!!! Potting soil is too heavy for delicate seedlings and it holds too much moisture.
The best homemade seed starting soil mix will contain the following ingredients: compost, peat moss or coconut coir, vermiculite, and perlite. Let’s take a closer look at these ingredients and why they matter.
1. Good-Quality Compost
Don’t just buy the cheapest bag of compost from the store for this seed starting soil ingredient. Those bags are cheap for a reason. Instead, get a good-quality bag of compost OR use homemade compost, which is free. Score! Here are my tips on how to make your own compost.
Whether you get a good-quality compost from a store or local farm or you use homemade compost, make sure it is a finished compost. We don’t want to see un-composted bits of food in there. And no non-aged manure, either. This needs to be dark, rich, finished compost. Screen your compost before using it in this seed starting mix to make sure you’re getting the good finished compost.
Some gardeners and gardening tips from a decade or so ago used to say not to use compost in a seed starting soil mix. It used to be believed that seed starting needed to use a sterile starting mix. There was a concern that the microbes in the compost would be too harsh for precious delicate seedlings.
However, it has since been shown that the nutrients and microbes and whatnot in the compost actually helps produce healthy seedlings and plants (learn more sciencey stuff on soil microbes here).
Expert Tip: If you want to super-boost your compost for a seed starting soil mix, add some good-quality worm castings in there, too!
2. Peat Moss OR Coconut Coir
Many homemade seed starting soil mix recipes contain peat moss. Peat moss is used for water retention in the seed starting soil. However, peat moss is currently not a sustainable resource. Tragically, it is being strip-minded from peat bogs around the world, which is just super super bad for the environment (read more about why peat moss is bad here).
A better alternative to peat moss is coconut coir. Coconut coir is a byproduct material from coconut husks that holds water just like peat moss. It is way better to use for the world’s health. IF you can find it. You will probably have to purchase some coconut coir online (here’s a good coconut coir option) unless you live in an urban area that is staying up-to-date with new gardening trends and environmentally-friendly gardening options.
Tragically, here in South Carolina’s rural upstate area, I could not find coconut coir at the garden stores (at least not at the ones I shopped at for the day). In fact, they had no idea what that was when I asked. Sigh. We’ll catch up someday, I hope. Since I needed my seed starting soil ASAP, I unfortunately had to use peat moss.
My advice for this seed starting soil mix is this: use coconut coir if you can find it and if you can afford it, but don’t beat yourself up if you have to make do with peat moss. Environment-guilt is a huge issue for me, and it can stress me out to the point of depression. I always have to remind myself to do what I can to help the earth but not to the point where I cannot enjoy gardening without immense guilt. Anyway, please don’t hate me for using peat moss this time….
Vermiculite is a natural mineral. It looks a lot like mica and is used in small amounts in seed starting mixes in order to help retain water. This is a super fine material and it is really light-weight. Seriously, my bag of vermiculite was huge and yet was super light to carry. Vermiculte helps the soil retain water and nutrients and release the nutrients when needed. It also helps with drainage and keeps your soil evenly moist.
By the way, use caution with vermiculite because it can be a lung irritant. Unless your lungs are super sensitive (if your lungs are sensitive, use a mask), basically, don’t dunk your head into the bag of vermiculite and you should be fine. And pour it into a container in a wide open space (like outside), not an enclosed small barn/gardening shed.
Perlite is a volcanic rock or glass that has been heated. It’s that white styrofoam-looking stuff you see in potting soil mixes. It adds drainage and air space to your seed starting soil. This helps prevent your seed starting soil from being waterlogged and lets your seedlings develop healthy and strong roots due to the air space.
You can usually find perlite right next to vermiculite at your local gardening stores. It’s slightly more expensive than vermiculite, but you get a lot in a huge bag, so it will last a long time. Since it’s an important item in homemade potting soil for container gardening and pots, it’s a good thing to have in your gardening inventory.
Homemade Seed Starting Soil Mix Recipe
- 4 parts compost
- 2 parts peat moss (or coconut coir: read above for details)
- 1 part vermiculite
- 1 part perlite
- In a wheelbarrow or a large container, mix up a batch of the ingredients. I used a bucket to scoop up 4 buckets of compost, 2 buckets of peat moss, etc. into my wheelbarrow.
- Mix the ingredients thoroughly. Run it through your hands: is it too heavy? If so, add a small scoop of vermiculite and perlite. Feel comfortable with the texture of the seed starting soil mix.
- Before you use it, moisten the seed starting mix. You want to make the starting soil mix damp but not soaking wet. I added a bucket of water, mixed it, and then felt it with my hands until I was satisfied with the moisture levels.
- Use your homemade seed starting soil mix in your preferred containers: pots, trays, seed flats, recycled cups, etc. Gently press it down as you fill your preferred containers. Top off as necessary.
- Follow your seed packet instructions for sowing seeds and enjoy the gardening season!
Are you starting seeds for the first time this year? Or is this your first year making homemade seed starting soil?
Tell me in the comments below ALL about your garden this year! I love hearing from you.
More Gardening Tips You Will Enjoy:
- Organic Soil Amendments
- Common Seed Starting Problems and Solutions
- How to Deal With Problems Growing Root Vegetables
- 10 Plants for Attracting Beneficial Insects to Your Garden