How to Make Your Own Seed-Starting Mix

Homemade Seed-Starting Mix Recipe

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Seed-starting mixes are essential for sowing many vegetables, herbs and flowers. But with so much to sow over the coming weeks and months, they can be expensive—unless you make your own. Here’s how!

Potting Mix for Seed Starting

Use the ingredients below in the quantities shown to make a good all-round potting mix for starting seeds. All parts are measured by volume, so you can use anything you like to measure your ingredients.

  • 2 parts compost. You can use your own garden compost, or buy some. Break up clumps with your hands or, ideally, sieve the compost for a fine texture. The compost will slowly release nutrients into the mix to help feed your seedlings as they grow.
  • 2 parts coir (coconut fiber), or leaf mold. If you’ve purchased a block of coir, soak it in water first until it’s fibrous and easily pulled apart. Alternatively, use well-rotted leaf mold. The coir or leaf mold adds bulk and helps to retain moisture.
  • 1 part perlite. Perlite makes the mix lighter and helps stop it becoming too wet.  You can use sand if you prefer, but this will give a heavier mixture.

Thoroughly mix all of the ingredients. Store it for later use in lidded container or in old potting soil sacks (or any other strong plastic sack) with the top rolled down and secured. Keep it in a dry, cool place.

Moisten the seed starting mix before you use it, so it’s damp but not dripping. Gently press it down as you fill your seed flats, plug trays or pots, taking care to fill right into the corners.

Sow your seeds according to the packet instructions, then water using a mister or a watering can fitted with a very fine rose. Alternatively, make your own watering bottle by piercing holes into the cap of a plastic bottle using a pin. This will provide a fine spray of water to gently water your delicate seeds.

Once the seedlings have germinated, water from below instead. Place containers in a shallow tray of water until the surface of the mix becomes moist, then remove.

Plants usually need potting on at least once before transplanting into their final location. When potting on you can use the same potting mix, or add worm compost or a balanced organic fertilizer for hungry plants such as tomatoes and cabbage family plants.

Container Potting Mix 

For growing plants in larger containers, mix two parts garden compost with one part coir or leaf mold. Add two or three handfuls of perlite per 10 gallons of the coir-compost mix to help improve drainage. Hungry plants will also appreciate a similar amount of worm compost, or mix in a slow-release organic fertilizer according to the manufacturer’s instructions.

For long-term container plants, include loam or good quality garden soil in your potting mix. Combine one part loam (or sieved garden soil) with one part garden compost, and add some slow-release organic fertilizer. This mix would be suitable for many containerized fruit trees, bushes and perennial vegetables.

See more about making your own potting soil.

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