How to Make Your Own Seed Starting Mix

Save money on starting seeds

Basil seedlings
Image by Chris Winsor / Getty Images

If you are a small farmer, buying pre-made seed starting mix can get a bit pricey. You want a quality seeding mix, but you don't want to spend a fortune. That's why many small farmers do not buy pre-made seeding mix. If you can buy the primary ingredients in bulk, it's easy to make a seed starting mix and not spend too much money on it. The best part is that you can tell exactly what is going into your seed starting mix, which is ideal if you are an organic farmer.

Why Make Your Own Seed Starting Mix?

It can be much easier to buy large amounts of the essential ingredients for seed starting mix than buying it already made. And you can use your compost to make seed mix—screen it first by passing it through a framed screen fitted over a wheelbarrow or other large container to sift out large particles, rocks, or other foreign material. Composting on your farm can save you a ton of money if you are composting. It can also reduce the amount of dust released into the air, making it less messy.

The other main reason small farmers choose to make their seed starting mix is the same reason they start from seed: to have control over the mixture and, ultimately, their food. Making your seed mix gives you more control over what goes into growing your crops versus buying a pre-made blend. Eventually, you may want to customize the ratio or add other soil amendments, such as garden lime (to make the soil more alkaline), sand (to allow for more drainage), or bone meal (to add more phosphorus), depending on that seeds you're planting.

Tip

Transplanting a seedling into the ground can be stressful for the plant. Compostable seeds trays allow for an easier transition. Plant the compostable seed pot in the ground where the growing plant will live in your garden. The wood fibers from the pot biodegrade, allowing moisture and air to get to the roots that can grow past the container. Using biodegradable trays eliminates the need to discard plastic pots. 

Recipe for Seed Starting Mix

This basic recipe for an indoor seed starting mix can be customized, sized up or down, based on the amount you need.

Tools

  • Wheelbarrow or large basin
  • Garden trowel, hand shovel, or spade
  • Water bottle or fine misting sprayer
  • Large container with an airtight lid
  • Gloves

Materials

  • Four parts of screened compost
  • One part perlite
  • One part vermiculite
  • Two parts sphagnum peat moss

The steps for making seed starting mix:

  1. First, gather all the materials.
  2. Whenever you are working with soil or compost, don gloves.
  3. Mix in the compost, perlite, vermiculite, and sphagnum peat moss in the wheelbarrow or bin. You can make as much or as little as you want. Some prefer working with "parts" terminology, or others prefer fractions: The mix is 1/2 compost, 1/8 perlite, 1/8 vermiculite, and 1/4 sphagnum peat moss.
  4. Lightly moisten ingredients with a finely misting water bottle or spray nozzle, then blend thoroughly using a hand shovel, trowel, or spade in a large container, such as a wheelbarrow.
  5. Whether you make your seed starting mix or buy a commercial soil for starting seed, store your leftover soil in an airtight container to avoid attracting bugs.

Designing a Seed Starting Mix

When making your mix, aim for something that balances moisture and drainage. If seedlings are too wet, they may suffer from damping off, a fungal disease that causes them to wither where the stem meets the soil. When this disease afflicts seedlings, they eventually fall over and die.

If you need a mix that drains more easily, use less compost and more peat moss or perlite. If you are looking for a mix that holds more water, add more compost or vermiculite proportionally.

Also, when using peat moss in your mix, you might want to add 1/4 teaspoon of garden lime for every gallon of mix to keep the pH balance in check. Garden lime is a rock powder that raises the pH balance in mixtures that are too acidic. Plants like daffodils, azaleas, rhododendrons, and hydrangeas are acid lovers and can forego the lime, whereas clematis, forsythia, lilacs, and crocuses would prefer more alkaline soil and appreciate the additive.

Peat Moss Alternative

Peat moss is a wonderful additive for soil mixes because it absorbs and retains water and nutrients, prevents soil compaction, it's sterile, and it's acidic (great for acid-loving plants). However, it has a major downside: peat moss is a non-renewable resource, and it best serves our planet remaining in peat bogs to combat climate change. Many alternatives can be used in place of peat moss, such as compost, coconut coir (coconut fibers), pine bark, PittMoss (recycled paper pulp), and worm castings.

Article Sources
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  1. Damping-Off. Utah State University Extension.