Starting seed time is one of my favorite tasks of the year, but it can be, without a doubt, an expensive time as well. Buying the mix needed to fill your pots can be costly. The alternative? Make your own seed starting mix.
On top of potentially saving you some money, you can create a unique blend tailored for each plant you plan to grow.
It’s easier than you think, so let’s dig right in!
Seed Starting Mix vs. Potting Soil vs. Garden Soil
Before you get started, it’s important to ensure you understand the difference between seed starting mix, potting soil, and garden soil. Not knowing the differences could lead to the death of your plants.
Luckily, it’s not hard to learn.
What Is Garden Soil?
The purpose of garden soil is to be put directly into your garden beds as an enrichment. It’s typically created with a mix of compost, fertilizer, topsoil, and other materials.
If you want to kill your seedlings, try starting seeds with soil from your garden or gardening soil you buy at the store. It’s a huge no-go!
Most garden soil is heavy and will compact down, trapping your seeds and smothering their roots. Also, most garden soil, whether you find it at the store or in your garden beds, has large chunks that aren’t ideal for seeds.
What Is Potting Soil?
The purpose of potting soil is as a base for plants growing in pots or containers. Potting soil is lighter than gardening soil, mostly due to the addition of perlite which prevents the soil from compacting.
While your seeds might not die, potting mixes often have chunks, such as pieces of bark, that retain too much moisture and allow too much air in, making it hard for seeds to germinate.
What Is Seed Starting Mix?
As you might imagine based on the name, the seed starting mix is designed specifically for starting seeds. It’s different from the others because it’s light and fine-grained, allowing the seeds to germinate and roots to establish.
At the same time, the mix won’t compact in the seed starting containers. It’s also designed to retain more moisture than other mediums.
The Benefits of Making Seed Starting Mixes at Home
If you’re like me, you always weigh the pros and cons of a project. I have to make sure that it’s beneficial for me, even if I factor in the time that it will take to source the materials and put it all together.
The main benefit of making a DIY seed mix is that it’s going to save you money. An average 8-quart bag, depending on whether it’s organic or not, can cost upwards of $10. That doesn’t seem too bad until you realize it’s not going to fill too many rows or pots.
Another benefit is that you control what ingredients you use. Some mixes that you can buy in the store contain chemical agents designed to hydrate the soil or give supplements to your seeds. That’s unnecessary, and if you’re an organic gardener, it goes against your plans.
Your Goals When Making Seed Starting Mix
You don’t want to just toss ingredients together and hope it comes out to be perfect. It’s good to understand your goals, so you can select the right ingredients and ratios.
- You don’t want your seed starting mix to be too high in nutrients. That might seem counter-intuitive, but high nutrient levels can harm your delicate seedlings.
- It needs to hold moisture without being soggy. If your seeds are too wet, it can cause them to rot or encourage the growth of fungal diseases, such as damping off.
- You need to be able to rehydrate or re-wet the mixture.
Common Ingredients in Seed Starting Mixes
Let’s take a look at the common ingredients you’ll find in seed starting mixes. All of the ingredients serve an important purpose.
Everyone knows that compost is similar to gold for your garden. It’s full of all the organic matter your plants need to grow and thrive. By using compost in your mix, you cover most, if not all, of your nutrient needs for your seedlings.
Coir, aka Coconut Fiber
Coir comes from coconut husks, so it’s a sustainable alternative when compared to peat or peat moss. Some gardeners feel concerned about using peat because the extraction process might cause adverse effects to the ecosystem.
Coir often comes in a block form, and you’ll need to rehydrate it by soaking it in a bucket of water until it’s easy to break apart.
Perlite is an ultra-lightweight volcanic glass and looks like white popcorn. Chances are you’ve seen it in different mixes from the store. By adding perlite, you improve drainage and aeration.
The purpose of perlite in your mix is that it lightens everything and improves air circulation. Some people use sand instead of perlite, but that does make the mixture a bit heavier.
Sphagnum Peat Moss
If you don’t want to pay for coir, sphagnum peat moss is a sterile, moisture-retaining medium that is fine in texture. Finer materials lead to a higher water-holding capacity.
One of the cons of peat moss is that it’s slightly acidic. If you’re concerned about the pH level of your seed starting blend, you can add garden lime to balance it out.
It also has some environmental drawbacks, as our guide explains.
This material is a natural mineral that is brown and granular in appearance. It’s added to seed starting mixes because of its water-absorbing properties that help to retain moisture in soil-less mixtures.
Seed Starting Mix Recipes
When you search the internet, you’ll find several recipes for seed starting mixes, so it can make it hard to decide which one to use. I suggest that you try a few! It took a few tries to find one that I liked the best.
Below are a few tried-and-true recipes that are well worth mixing up!
For each, try varying the ingredients based on your seed’s requirements. For instance, for thirsty seeds, add more vermiculite.
It’s important to know that parts are measured by volume, so you can base the parts on how much you’re making. If you’re making a small amount for a few plants, you might only use cups, but large quantities could be quarts or gallons. It’s up to you!
Also, you don’t have to be exact; I’ve never measured out the ingredients. Try to be consistent, but there is no reason to measure things out perfectly.
- 2 parts compost
- 2 parts coir
- 1 part perlite
Use your hands or a garden trowel to mix all of the ingredients together thoroughly. It needs to be a consistent mix with the ingredients distributed as evenly as possible.
- 2 part sphagnum peat moss
- 1 part perlite
- 1 part vermiculite
Put all of the ingredients into a clean tub and saturate with water. Add as much water as the mixture will absorb. You’ll be surprised by the amount you need to add because peat moss can absorb up to 26 times its weight in water.
That’s a lot of water.
It might seem strange to do this but this first watering helps to keep the mixture moist because peat moss can be hard to re-wet if it’s totally dried out.
Once you complete this step, fill your seed starting containers or trays and get started.
- 1 tablespoon garden lime (if you use peat moss)
- 8 parts coco coir or peat moss
- 1 part vermiculite
- 1 part perlite
Premoisten your peat or coir. Mix all of the ingredients together thoroughly.
How to Store Homemade Seed Starting Blends
If you make your own mix, you’ll need to store your leftovers in an airtight container to stop bugs from getting inside of it.
The best option is to use 5-gallon buckets with air-tight seal lids. Another option is a mylar bag that you can seal to be airtight, but it’s more expensive this way.