How to Make the Best DIY Seed Starting Mix - Backyard Boss
We are reader supported. External links may earn us a commission.

How to Make the Best DIY Seed Starting Mix

Planting season is here and for most of us, that means getting a good, beneficial seed starting mix is crucial for that quick germination of seeds. You can purchase some mix from your local nursery or someplace like Amazon, or you can make your own. Personally, I prefer everything from scratch, so a DIY seed starting mix is the perfect thing.

What Do Seeds Need to Get Started?

For healthy, fast growth, seedlings prefer a growing medium that helps with a number of things. The precise ingredients of the mix should vary depending on the plants you’re growing. But, basically, your seeds need ingredients that provide the following benefits for them to germinate quickly.

Proper Drainage and Water Retention

Ever heard of root rot? Unfortunately, this nastiness is fairly common in plants that don’t receive proper moisture balance in the soil in which they’re planted. There needs to proper soil drainage as well as moisture retention to help seeds start and stay strong as they grow into the beautiful plants you’re looking for.

Perlite and pumice are most commonly used for this purpose. They prevent compaction of growing medium, meaning air and water can properly flow through. Vermiculite, on the other hand, retains moisture for longer periods of time than soil, so it’s a valuable asset in your mix, as it allows seeds to draw water longer.

Get Perlite

Get Pumice

Get Vermiculite

Plant Food or Compost

Not all species of plants need or want food in the earliest stages. To determine what your seeds want, study up on the specific plant and decide whether or not to include some kind of plant food in your starter mix.

The Best Bat Guano Fertilizer


Peat moss or coconut coir may be the best source of nutrients in the starting mix you create. They don’t actually create nutrients, but they hold onto them for plants to draw from. Again, the variety of plants you’re growing will determine which options are best. Most plants do well with at least some combination of these items, however, which can be found in a general starting mix recipe (like ours below).

Get Peat Moss

Get Coconut Coir

Acidic Adjustment

If you’re using peat moss in your recipe and the plants need to avoid acid (which most do), some garden lime may well be required to reduce the acid for speedy, healthy growth.

Get Garden Lime

What’s the Difference Between Starting Mix and Potting Soil?

potted plants on a desk

Potting soil and seedling mix are two very different things, despite being “soil for plants.” One, potting soil, is a growing medium made up of topsoil and a combination of perlite, vermiculite, peat, manure or compost, or humus. Many also contain fertilizers.

Seed starting soil, however, is a (usually) soilless planting medium that is more ideal for germinating seeds. These mixes often contain some combination of coconut coir, vermiculite, perlite, or peat moss. They do not contain soil or compost, though, as these may carry fungal or bacterial components that can prevent proper seed growth and root development.

DIY Starter Mix – Our Recipe

This general seed starting soil blend is great for most varieties of plants, from flowers to vegetables.


  • 8 parts coconut coir
  • 1 part perlite
  • 1 part vermiculite
  • Water

If the seeds you’re planting should have compost included in the mix, add 2 parts compost.

Note: If you’re not sure what a “part” is, this is simply a generic unit you convert to the amounts you require. In this case, we have 10 parts. If you need 10 cups of planting medium, then 1 part equals 1 cup. If you need 20 cups, then 1 part equals 2 cups.

Step by Step How to Make Your Own DIY Starting Mix

  1. Choose a large container, ideally at least 1/3 larger than the total volume of medium you’re mixing. (A wheelbarrow or giant planter are good options.)
  2. Dump the ingredients into the container and, using your hands or hand cultivator to thoroughly mix the ingredients until combined evenly.
  3. Next, add some water. Add enough water to moisten but not soak the soil.
  4. Let the mix expand a bit – probably 5 to 10 minutes.
  5. Once the mix has expanded, portion out your mix to your seed starting pots as needed.

lettuce planted in soil

Better Growth With the Right Mix

For the best results possible, be sure to study up on the seeds you’re planning to grow. Most will benefit from the above recipe for a basic starting mix. Some may require some compost, as mentioned, but others will do best with an even simple starting medium like pre-moistened plain coconut coir. The right soil for seedlings can make all the difference in your gardening efforts.