Tips for Storing Homemade Seed Starting Soil Ingredients

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Almost one year ago today, I made my favorite and very successful seed starting soil for the first time. Not only was it a fraction of the cost of pre-mixed potting soil, it was at least as good as anything I have purchased in a bag. I actually like it better than anything I have purchased. Here is the recipe:

• one part vermiculite
• one part perlite
• one part sphagnum peat moss
• one part composted steer manure

The size scoop or measure you use doesn’t matter. It is the ratios that count. Although, it’s not like measuring flour for baking cookies. It doesn’t have to be exact. There is a fair amount of dust, particularly from the perlite. I find it helps to put the perlite under the other ingredients, but then also add a fair amount of water before starting to mix it.

The whole mix absorbs quite a bit of water, so if it is still uncomfortably dusty when you are first mixing, don’t be too worried about adding more water. If it ends up more damp than is best (that is, more damp that thick oatmeal), you can let it sit a minute so that a lot of the extra liquid settles on the bottom. Then, after you have used the top, less watery soil, you can add a round of ingredients to help absorb the extra liquid.

I bought one bag of the manure, one block of the peat moss, and had the vermiculite and perlite on hand. Even with upwards of 15 trays of seedlings, as well as pots for starting dahlia tubers and plumeria cuttings, I had significant leftovers of everything. I had some plastic bins sitting around, so I put the manure, perlite, and vermiculite in those for storage. I left the peat moss in the bag, since there was still enough that it was keeping its convenient square shape.

I put lids on partly because I let my cat into the greenhouse every night, and you know about cats and their bathroom habits. But, also, the bins have lids and it just seemed like the natural organizational things to do.

That was fine for the perlite and vermiculite. Nothing changed about them. Let me add here that you may be wondering why I use both of these ingredients. When you read various recipes, it will often say use one or the other. I found that just using one or the other was not optimal. When I added them both I got the consistency (perlite) and water retention (vermiculite) that I wanted. It is hard to see the difference in them in the photos, but close up you can tell they have different properties.

The peat moss got so dry sitting in the greenhouse that when trying to use it this year, it has been like breaking clay apart. I have ended up first breaking it in chunks small enough to put in a bucket. Then, I chop it with the tip of my hand trowel. This is not my favorite thing. I’ve tried adding some water to the whole square, but it just rolls right off. I may try to put the smaller chunks in a closed container with a lid and see if I can get it to soften some that way. Kind of like what you do with brown sugar that has gotten hard. In the final mixing, I have still found clumps that I just crush with my hands. After these efforts, it is still mixing in well this year.

The manure kind of had the opposite problem. It was growing some streaks of white mold, which is risky for seedlings. For that problem, I left the lid off of the container for a couple of weeks and it seems to have disappeared. So, I guess that in the future, I should try to find a screen style lid for the manure bin.

Now that I have my own horse’s manure composting pretty decently, I may be trying to use that for the manure portion of the mix. That will require more labor, though, as there are larger bits of debris and rocks in it from where the chickens work on it. I’ve seen my dad use a screen for those sorts of things, so I might consider that.

I just got done with my second round of seed starting this year. The first batch is sprouting. The second batch includes these cape daisies, a regular of mine. I will make myself wait a couple more weeks to start the faster sprouting stuff.