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Save money by mixing your own seed-starting soil

Apr 02, 2012

Have you priced seed-starting mixes recently? If so, you're wallet is probably feeling a bit gouged. If you take the time to mix up some seed-starting mix for yourself, you will save some serious cash over the long run.

Let me start by explaining what I use, and then I will tell you why I chose the materials that I did.

Homemade seed-starting mix:
50% peat moss combined with
50% vermiculite
and make sure to thoroughly wet the soil prior to use (I prefer very warm water), and make a choice about fertilizer (see below).

The peat moss not only holds water, but staves off fungal infections because of its slightly acidic pH. It also serves as a soil conditioner in my particularly clayey soil. There is some controversy over the harvesting of peat moss, and if you have the option, you can purchase coconut coir instead. The absolute cheapest way to purchase peat moss is to buy a big bale from a gardening or hardware store, but if you don't want to venture out to find it you can find peat moss online.

The vermiculite's function is to hold water, air, and nutrients. Plants do require some air at their root levels, and the vermiculite will also bind nutrients when you decide to fertilize. You can purchase perlite in lieu of vermiculite, but I don't like the way that perlite tends to float to the top. It is cheapest to purchase vermiculite in the largest sacks you can afford. This vermiculite link on Amazon appears cheaper than anything I can find locally (including shipping).

Fertilizer: Some recipes incorporate some type of organic fertilizer, but if your soil is sterile, it will not be able to break down the fertilizer into substances that your plant can use, which means that the addition of fertilizer is useless. Further, the addition of fertilizer that cannot be used will increase the salinity, and "burn" your plants. When gardeners say "burn" a plant, they really mean that the salt content is so high that it will cause your plants to dehydrate. This means that you will likely over-water your plants which will cause the soil to drop (plants don't like cold soil), and encourage fungal and bacterial infections.

I prefer to feed my plants well after their leaves form. This is because a seed actually has its own fertilizer reserves, and me messing around with fertilizer is only going to increase the salinity of the soil. When you fertilize, you have organic options and you have synthetic versions, both of which have their own pros and cons.

Organic fertilization: since the soil is sterile, you will need to choose a fertilizer that has "composted" or converted to a form that a plant can use. The only organic fertilizer that I know of that contains nitrogen readily available to plants is fish emulsion . Unfortunately, fish emulsion stinks bad, even if it is supposedly deodorized. Only part of the emulsion has been converted to a usable form, and the nutrient balance is way off. Some gardeners like to use liquid kelp to partially offset this imbalance. Kelp is wonderful in the garden, but most of the micronutrients (which is the real reason kelp works so well in the garden) aren't terribly useful to seedlings.

Synthetic: the one time I strongly prefer using synthetic chemicals in my gardening is in fertilizing my seedlings. The reasons for this is that the fertilizer is far cheaper, all of the nutrients are readily available to the plant, and the nutrient balance is much better than in organics. Not to mention the smell doesn't make you want to throw up! A small box of Miracle Grow is going to last you a looong time. Be sure to use only about 1/4 or less of what the box recommends to make sure that you don't over-salt your plants.

Furthermore, some folks just choose not to fertilize until they pop their plants out into the garden. But, if you live in a short-season climate, it is probably best to give your plants a head-start.

So why we should be using a seed-starting mixture versus regular old garden soil? The reason for this is mainly that with regular garden soil comes fungi that cause damping-off diseases or just causes the seed to rot instead of germinate. There are other reasons, but this is the main one. Here in my heavily shaded, damp climate with clayey soil, I find that I cannot get away with using garden soil at all in my seed-starting mixtures. Since my soil is so clayey, the addition of the homemade potting soil is beneficial.

Do you mix your own seed-starting soil or potting soil?

Be sure to enter my vegetable seed giveaway!


I use rice hulls mixed with compost to start most of my seeds. Rice hulls are available cheap or free, and break down to provide nutrients. I also use them for mulch, and add them to my compost piles. Rice Hulls Rock!
where do you get them for free?

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