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.

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March 15 2011      41 comments     Linda Ly
Jardín   Proyectos   Semillas

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  • The Plumbery269

    I hope you are aware the ink used to print newspapers etc. contain lead. Just thought you should know

    • Decades ago, heavy metals in newspaper inks were common when newspapers were set in lead type, but these days, most newspapers (especially the major ones) use soy-based ink out of health concerns for their workers. This report by the USDA states that both b/w and color-inked newspapers can safely be used for mulch in vegetable gardens: https://semspub.epa.gov/work/05/79213.pdf

      If you’re worried that your local newspaper may still be using heavy metals in their inks, you should call them to verify.

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  • WatchingThe End Of Democracy

    I use this seed start mix. it does a good job germinating the seeds, The problem that I have is when I go to transplant the seedling, the soil falls apart. I do soak before transplanting. Is there anything that can be added to the mix so it will stick together better?

    • It’s a very loose mix, so it’s not meant to stick together unless you really pack it into your pot. You can try increasing the amount of peat used, but it’s not a problem for the mix to fall apart when you transplant (assuming you’re transplanting into soil anyway).

      • WatchingThe End Of Democracy

        Thank you for getting back to me so quickly. 🙂 I will add more peat. I was just concerned that the roots were being damaged when the soil fell apart as I tp. Again thank you for your hard work and knowledge that goes into this website. 🙂

    • Ron Nichol

      I germinate only in vermiculite then start feeding with 1/2 strength fertilizer when the first true leaves start forming. Shortly after that I transplant into potting soil. The secret to transplanting from vermiculite is to get just the right degree of dampness: too wet or too dry is not good (but also not deadly to the seedlings if you’re careful. The day before I transplant I fully water the seedling plugs (which are in single cells). After drying for a day, the plug can be easily removed from their plastic cells and placed in a bigger pot with soil.

      My seedlings are placed in a clear, enclosed, plastic container that sits on top of a heat mat. If yours are not heated or are uncovered, they may be ready to be transplanted in less than 24 hrs.

      I expect that the same principles would apply to a germination mix of vermiculite, coir, peat moss and/or compost mixture.

  • Rajiv S

    Hello Linda, This is an Excellent Article I came across via google search regarding potting mix. Thanks!

    I have always used combination of Sand (80%) and Vermi Compost (20%) as potting mix and I do add Bone meal and Neem Cake relatively in small proportion. Additionally I use NPK fertilizer (foliar spray) along with Micro Nutrients. This has fetched me good results so far but the disadvantage I feel is, container gets very heavy because of sand (I am into terrace gardening) and I need to regularly water the plants.

    For past few days I was reading about Soilless Potting Mix/Enriched Potting Mix and now I am more inclined to use Coco Peat (which is very easily available in India), Perlite as well as Vermiculite because of their properties and hopefully it will reduce a lot of weight of the container, will provide good drainage and because of their water retention property, it may reduce the watering cycle. I will continue to use some part of sand as it provides stability to the plant.

    Regards

    • Sand is very fast-draining, which is indeed a disadvantage if you’re using it for a potted plant that needs regular watering. I typically use a sand mixture for cacti, succulents, and other low-water plants.

      Good luck with making your own mix with coco peat, I believe you’ll have better results with that!

      • Rajiv S

        Thanks Linda! I am now using the composition of “Enriched Potting Mix” and beginning to see good results. Also the “seed starting mix” composition is showing very good results. I sowed Coriander (Cilantro), Fenugreek and Spinach a week back and they all have germinated well.

        Starting to use Enriched Potting Mix for Tomato, Brinjal (Eggplant) as well as Chilli (Hungarian Yellow Wax variety), they all are in a container, will transplant them.

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  • Tushar Sethi

    Hi Linda, I have used enriched potting mix for my seed starting is it ok?

  • BT RAO

    Hello Linda,
    Just came here from google search, and happy to read your guide on potting mix.

    But i have one doubt, please kindly clarify.
    I bought Coco coir compressed brick of 5 KG weight, which can expand to 60/70 liters on adding water. How to measure coir in this case as in dried form or expanded wet form measn have to take water mixed coir to measure?
    I really appreciate your help in clarifying this.
    Thanks

    • It does not have to be an exact amount. Just eyeball equal portions of dry coir, vermiculite and perlite, then thoroughly saturate the mix with water before using.

      • BT RAO

        Thank you!

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  • Biplab

    Hi Linda,

    I am from Kolkata, India. I have some hibiscus plant and some lemon plant in my Flat Balcony. They are used to get 6-7 hrs of Sunlight. But I am having problem like Leafs are becoming Yellow and also they are dropping from plant. What can be the cause and how to overcome from this problem. Any Idea. Thanks in Advance.

    • Sorry, it’s hard to know since yellow leaves can mean so many things. Perhaps underwatering, overwatering, or a nitrogen deficiency.

      • Biplab

        For Nitrogen which type of Food I can apply?

        Also one more thing I want to know that, for Rose tree how to prepare Potting Mix. It will very helpful for us if you let me know about this. Thanks in advance.

        • If you don’t know the problem with your plants, an all-purpose fertilizer would be best. Choose one that’s fairly balanced in its N-P-K values. Or add compost, compost tea, or fish emulsion.

          And I’m sorry, but I’m not familiar with growing roses.

  • Ravi Theja

    Hi,
    I’ve been using this potting mix but one problem i encouter always is that my seedlings tend to wilt off!
    What could be the reason?

    • The wilting (damping off) is caused by different kinds of fungi. If your seed starting mix is sterile (never reused and always mixed with new ingredients), the fungi could come from pots or tools that haven’t been cleaned. Sometimes the fungi could be reintroduced via gloves, clothes, or other items that might come in contact with your seedlings.

      • John Gabriel Arends

        What do you do with the potting/starter mixes from previous years if you don’t reuse it? Do you know of an affordable source to get these ingredients?

        • I store unused potting mix in a covered container. You can use a lidded trash can or plastic storage bin (or something similar) for this. Mine just stays outside next to my potting shed.

          As for affordable sources, I get all of my ingredients from one of the local nurseries. They tend to have a larger (and better) selection than a big box nursery like Home Depot.

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  • 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 🙂

    • Yes, you can sprout any seeds in the soilless mix, but eventually you’ll need to fertilize the plant or amend the soil if you want it to thrive.

  • 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.

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

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  • 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.

  • AshleyWaterstradt

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

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  • 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, lol..plus 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, traveldesignery.com is where i’ll be!)
    —Lorena

    • 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!

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