The foundation of your seed-starting mix determines its texture, water retention, and nutrient availability. Choose one of the following for your base:

Compost (Sifted, Well-Aged, Fine Texture)

• Why Use It? Compost adds nutrients to your mix and fosters healthy seedling growth. However, it’s best used for outdoor seed starting.
• Pro Tip: Avoid compost for indoor seed-starting as it may introduce unwanted pests or pathogens.

Coco Coir

• Why Use It? Coco coir is lightweight, holds water well, and expands when hydrated, making it an excellent seed-starting medium.
• Pro Tip: Always hydrate coco coir before mixing to ensure even water distribution.

Peat Moss

• Why Use It? Peat moss is a common base for seed-starting mixes, known for its excellent water retention and light texture.
• Pro Tip: Peat moss is acidic. To balance the pH, add 2 tablespoons of dolomitic lime per gallon of peat moss.

A good seed-starting mix isn’t just about the base. These key ingredients improve the mix’s structure and nutrient-holding capacity:

Fine Vermiculite

• What It Does: Vermiculite holds onto nutrients and water, ensuring your seedlings get consistent moisture and nourishment.

Fine or Ultra-Fine Perlite

• What It Does: Perlite improves drainage and prevents soil compaction, keeping the mix light and airy for healthy root development.

Here’s the ideal ratio for a seed-starting mix::

1. Base Material (8 parts): Choose compost, coco coir, or peat moss as your foundation. For every 8 parts of base material, adjust the other ingredients accordingly.
2. Perlite (1 part): Add 1 part fine or ultra-fine perlite to improve drainage and prevent compaction. You can increase this slightly if the mix feels too heavy.
3. Vermiculite (1 part): Add 1 part fine vermiculite to retain moisture and hold nutrients, ensuring your seedlings stay consistently hydrated.

Pro Tip: Mix everything thoroughly to ensure even distribution of ingredients. Hydrate the mix lightly to create a moist, but not soggy, consistency before adding seeds.

Making your own seed-starting mix doesn’t just give you control over quality—it’s also cost-effective. Let’s break it down with a couple of examples:

Example 1: Using Coco Coir as the Base

• Base Material (8 parts): Coco Coir (~$10 for a brick, expands to make 32 quarts) = ~$0.31 per quart.
• Perlite (1 part): (~$20 for a 16-quart bag) = ~$1.25 per quart.
• Vermiculite (1 part): (~$25 for a 16-quart bag) = ~$1.56 per quart.

Total Cost for 10 Parts: Approximately $5.42 for 10 quarts of mix, compared to $10–14 for pre-made mixes.

Example 2: Using Peat Moss as the Base

• Base Material (8 parts): Peat Moss (~$15 for a 3-cubic-foot bale, approximately 90 quarts) = ~$0.17 per quart.
• Perlite (1 part): (~$20 for a 16-quart bag) = ~$1.25 per quart.
• Vermiculite (1 part): (~$25 for a 16-quart bag) = ~$1.56 per quart.

Total Cost for 10 Parts: Approximately $3.94 for 10 quarts of mix, offering even more savings compared to $10–14 for pre-made mixes.

Make It Your Own:

To tailor this cost breakdown to your situation, use our Seed-Starting Mix Cost & Comparison Calculator to input your local prices and calculate your savings!

​Click here to grab your calculator.​

• Balanced Water Retention: The combination of the base material and vermiculite ensures your seedlings stay hydrated without waterlogging.
• Improved Drainage: Perlite keeps the mix airy and prevents compaction, promoting healthy root growth.
• Nutrient Accessibility: Vermiculite and compost (if used) provide consistent access to essential nutrients, giving your seedlings the best possible start.