How to Make Your Own Seed Starting (and Potting) Mix

Perlite, vermiculite and sphagnum peat moss

Now that you’ve made your own recycled newspaper pots, it’s time to fill them up. If you plan to grow a lot of seedlings, making your own seed starting mix is a snap and it can be used as a basis for potting mix after. Even if you only need a small bag for your windowsill tray, you can refer to these ingredients as a guide for buying a commercial seed starting mix.

Certain store-bought mixes contain synthetic fertilizers and wetting agents, which defeat the purpose of growing organically. Seed starting only requires a minimal soilless mix, as seedlings do not need fertilizer until they develop their first “true set” of leaves. When the true leaves emerge, you can supplement the mix with your own organic fertilizer. After all, it’s always good to know what’s going in your garden — and eventually, your food.

Seed Starting Mix

  • 1 part sphagnum peat moss (or coir)
  • 1 part perlite
  • 1 part vermiculite

A “part” refers to any unit of measurement to make the quantity you need, as long as it’s consistent: a scoop, a bucket, or a bag of each ingredient.

Mix equal parts of all ingredients together

Combine all ingredients in a clean tub or bucket, and water down the mix. It should be moist, not soggy. This initial watering makes it easier to keep the mix uniformly moist throughout the seed starting period, as sphagnum peat moss can be difficult to re-wet if it’s been left to dry out in a pot.

Fill your pot with seed starting mix

Sphagnum peat moss (not to be confused with the coarser and more fibrous sphagnum moss that’s typically used to line floral baskets) is an excellent, sterile, moisture-retaining medium. Coir is similar to sphagnum peat moss in terms of look, feel and retention, but is made from the fiber of coconut shells. Perlite is an ultra lightweight volcanic glass resembling white popcorn ceiling, and provides drainage and aeration. Vermiculite is a natural micaceous mineral, brownish and granular in appearance, with water-absorbing properties that facilitate re-wetting of the soilless mix.

Fill your seedling pots with this homemade mix, add seeds, and sprinkle a thin layer of vermiculite over your seeds if they need to be covered.

Fill your pot with seed starting mix

If you have ingredients left over, you can save them for next season, or make a potting mix for your transplants.

Basic Potting Mix

  • 6 parts sphagnum peat moss (or coir)
  • 1 part perlite
  • 1 part vermiculite

Enriched Potting Mix

  • 4 parts sphagnum peat moss (or coir)
  • 2 parts compost
  • 1 part perlite
  • 1 part vermiculite

You can take it even further by amending your potting mix with bone meal, blood meal, lime, and a host of other supplements, depending on the nutritional needs of your plants. But if you’re more gardener than chemist like I am, it’s fine to keep it simple and just supply your plants with a lot of old-fashioned love, sunshine, and water.

Never Miss a Post!

March 15 2011      14 comments     Linda Ly
Jardín   Proyectos   Semillas

Interested in
advertising in this space?

Contact us
for our current rates!
  • Pingback: Garden - Small Bird Studios

  • josey

    Hi Linda, Could you grow grass out of yoiu soilless mixture ? EG: if i created the mixture could i then add grass seeds to it and it will grow ? Thank You ! & great blog :)

  • Kristin

    Dear Linda: Can I start these seedlings outside rather than in the window of my apartment where I have such limited space? Thank you.

    • Linda Ly

      Sure, as long as it’s warm enough outside to germinate the seeds.

  • Pingback: A Lot Can Happen in 10 Days | Garden Betty

  • Pingback: Starting Seeds in Coffee Filters (or Paper Towels) | Garden Betty

  • Andre David bowers

    HI Linda, I’ve been readign your bog entries, ideas on gardening , potting soil ideas, even the chicken tiki coop. I was about to post a pic of my hot Portugal Peppers and my cukes  but hmmmm I guess you don’t accept photos of other people’s  gardens, harvest etc. Thats Ok , I just wanted to say hi and   I enjoy  your ideas as  well as th erecipies  too!  Best of luck in the future with  your blog.

    • Linda Ly


  • AshleyWaterstradt

    Gah! I wish I had seen this before starting all my seeds! lol 

  • Pingback: Starting Seeds in Eggshells… Cute and Yes, Even Practical | Garden Betty

  • Pingback: How to Repot Tomato Seedlings | Garden Betty

  • Pingback: The No-Brainer Guide to Starting Seeds Indoors | Garden Betty

  • Lorena

    How creative! it would be nice to have the extra space for things like this, but very difficult in nyc :-( … would love to have a whole garden with little herbs, flowers and gadgets.
    I love the concept of your blog! and you surf, how cool!..i wish i was brave enough but i think i’d break in half, I basically just learned to swim..
    (p.s. thank so much for your comment! i changed my web name in case you want to follow the new one, is where i’ll be!)

    • Linda Ly

      Haha I know, I used to live in NYC and the extent of my gardening was a couple of little pots on the fire escape!

      Thanks for stopping by and I’ll be sure to bookmark your new URL!