Commercial vs. Homemade

“But of course a commercially formulated growing mixture is going to be better than something I make at home.” How many times have we said, or at least thought, this same thing? I certainly have. The assumption is that what is commercially available has been well researched and thoroughly tested. As much as I try to stay focused on the basic concepts of Southern Agrarianism, the influences of modern-day American society are a powerful force to overcome.

Several weeks ago, I started this year’s garden project – to plant several varieties of tomatoes and decide which variety I will be focusing on. As usual, the seeds were planted in soil blocks. I would be taking careful notes throughout the life of the plants. Unfortunately, a careless mistake a few hours after planting resulted in losing track of which variety is planted in which block. I ended up having to start over. Fortunately (or perhaps unfortunately), I had already prepared a commercial seed starting system for another project. I decided to press that into service for the tomato project.

I ended up with two groups of tomato seeds. They were planted hours apart using seed from the same seed packets. Although it wasn’t part of the original plan, this would be a good opportunity to see how my homemade seed starting mixture and soil blocks compared to a commercial seed starting system, since all other factors were the same.

Commercial seed starting trays and commercial seed starting mixture.

Homemade seed starting mixture formed into soil blocks.

In this case anyway, homemade clearly wins over commercial. The seedlings in the PVC (Peat/Vermiculite/Compost) mixture and soil blocks are over double the size, have twice the number of leaves, and have much thicker stalks than those started in the commercial mixture. They were watered at the same time and the same rate, and were set side-by-side under the grow lights and timer. Here are the details:

Commercial System:
• Ferry-Morse seed starting plastic trays
• Jiffy Organic Seed Starter Jiffy-Mix

Homemade PVC (Peat/Vermiculite/Compost) mixture:
• 2 parts Peat Moss
• 2 parts medium Vermiculite
• 1 part Mushroom Compost
The Peat Moss and Mushroom Compost were sifted to remove any stick or large pieces.

Summary
I suspect that much of the difference comes from the Mushroom Compost that I added. I suspect that Black Cow composted cow manure would work just as well. Since this was used in soil blocks, the physical consistency was also important, and the compost helped hold it together as well as providing nutrition to the seedlings. The instructions in the commercial mix call for applying fertilizer after the seedlings have been transplanted into the ground. It is clear to me that this is a much better way to start seedlings than using a commercial mixture in the plastic trays. If I were inclined to use the plastic seed starting trays, I would try them using my PVC mixture in the plastic trays rather than the soil blocks, but I see no advantage in using plastic rather than soil blocks.

The PVC mixture is nothing special. It was not the result of careful research – it just seemed like a good mixture adapted from what I currently use in our raised bed garden. I am planning other test mixtures, but that mainly involves improving the handling characteristics of the soil blocks rather than the nutrient levels. Most of the soil block seed starting mixtures I have seen are a lot more involved than my PVC mixture. I wanted something simple to put together using readily available materials.

I have since started another batch of seeds using the PVC mixture and soil blocks, only this time they are carefully identified as to which variety is planted where. I’ll publish the results of my testing later this year.