Save Money - How to make your own professional seed-starting soil mix

 

I'm planting my first seeds today and to do that I'll need to mix up a new batch of seed-starting soil mix. If you're starting your own seeds in trays like me you need to use a soil "medium" that is sterile, meaning that it doesn't have fungus and bacteria that will be hard on your tender little seedlings, especially in the humid conditions that are ideal for seed starting. 

You can buy seed starting mix at your local garden supply store or, as I've learned, you can make your own that is just as good if not better. It will take an initial investment but if you're going to get into starting plants I think it's worth it and if have a large volume of seeds to start and transplant as they grow you'll save some money by making your own.

To get started you need to buy three basic ingredients:

    - Vermiculite

    - Perlite

    - Peat Moss

I buy the big bags of each for around $25 each at Northwest Seed and Pet, and those usually last me two growing seasons, with the perlite and vermiculite lasting longer. I find that I don't need much soil medium to start the seeds, but when I transplant the growing plants into larger pots I really use a lot of soil medium.

The basic mix is 3 parts peat moss, 1 part perlite and 1 part vermiculite. I make my batches by using a plastic pitcher, and I use a dedicated garbage can to mix 9 pitchers full of peat moss, 3 of perlite and 3 of vermiculite. Note: use a particle mask while doing this. I usually wet it down a little before mixing it to keep the dust down.

Make sure to mix it up well, wet it all down so it's damp, but not soggy, and it's ready to load into your planting trays. It's much easier filling plastic trays with soil that already has the proper moisture content.

I learned this mix from Bruce at GEM Garden and Greenhouse. He sells this medium with some other goodies added in for a great price. If you're only starting a couple of trays you might want to go that route.

Seedlings supply their own fertilizer for the first week or so as they feed off the remnants of the seed. After this you will need to use a regular regimen of fertilizer to help them grow. Take note that peat moss is slightly acidic so, depending on the sensitivity of the plants you're starting, you may want to compensate in your fertilizing to neutralize the acidity.

I've used this seed-starting mix for four years with great success. Let me know if you have any questions.

Photo: From an amazing photo collection of vintage seed packs and catalogues at the Smithsonian.

Comments

[Charlie]

Thanks for this great info. I've always wondered why one would start the seeds in small pots/trays and then transplant to a bigger pot. Isn't transplanting hard on the plants? Why not just start them in the bigger pot that they will be in for the entire greenhouse time?

[craig]

Charlie,
I start my seeds in seed trays that I put on heat mats to help facilitate germination. The seed trays also allow me to start a lot of seeds in a small space and space is a premium in a small greenhouse like mine.
Transplanting is not hard on most plants - with squash plants being the exception. They don't like to have their roots messed with. Most other plants are stimulated to grow by tussling the roots a little bit when you transplant.
Craig

[Jake]

Why use an unsustainable product like peatmoss...