Seed Starting Soil: Density, pH, Sterilization, and DIY Mix Recipes

Seed starting soil is often overlooked, but density, pH, fungi, and insects make or break success.

Density

Clay-heavy soil suffocates new roots. Sand/loam mixes drain better. Add perlite to lighten.

pH

Each plant has a range. Test kits available; adjust with peat moss (lower) or wood ash (raise).

Sterilization

Bake at 250°F for 1 hour—kills fungi, molds, insects, weed seeds. Smell dissipates.

My DIY Mix

1. Screen ½ wheelbarrow soil (¼" mesh) to remove stones, weeds.
2. Fill 4 baking pans, bake.
3. Mix in filler: perlite, ground straw, or fine sand (whatever's handy).
4. Test/adjust pH.

Commercial Mixes

I prefer them, but bake if germinating fragile seeds or mix looks suspect. Microscope users can inspect instead.

Seed starting is addictive—get the soil right, and the magic begins.