The Southern Agrarian

Southern Agrarianism and the culture of the Old South

Tag: soil blocks

A Different Way to Start Seeds

My standard method of starting seeds has been to use soil blocks – a molded block of soil with no container to keep it together. I have excellent results with them, but they tend to be rather fragile and require extra care to make sure they don’t fall apart. In addition, the process of making them is a bit more labor-intensive – not a lot, but it’s enough to cause planting to be put off until a larger block of time is available.

Yesterday, I planted a tray of 50 seeds using 2″ cube seed pots (Note that although the product is great, their delivery time is very slow). Unlike so many seed starting containers, these are a heavy duty plastic that should last for many years with decent care. Fifty of them fit perfectly in a standard 1020 (10″ x 20″) seedling tray.

After filling and compressing the soil into the seed pots, I soaked the soil well. After an hour to let the moisture work its way through the soil, I used the end of a Sharpie marker to push a small indentation into the soil in each pot. The seeds were added (one per pot – I try to avoid multi-seed planting), and then covered with some medium Vermiculite, then lightly watered again.

This batch included 20 Bell Peppers (California Wonder), 20 Egg Plant (Black Beauty), and 10 Squash (Early Prolific Straight Neck). As I usually do, I drew up a diagram of the seeds in the tray so they would not get mixed up. Popsicle sticks mark the borders between different seed types. The trays are now setting on the seed heating pad and covered with a clear plastic top to retain moisture, so I should see green in the next few days. As soon as they begin to sprout, the tray will be moved under the lights.

Like much of what I do here, this is an experiment. I mixed a small handful of organic fertilizer in with a 5 gallon bucket of ordinary potting soil. There was nothing precise about this – my goal was to have a quick and easy way to plant the seeds. This was an experiment of necessity, since this should have been done at least a month ago.


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.

Commercial seed starting trays and commercial seed starting mixture.

VPC seed starting mixture formed into soil blocks.

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.

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.

Soil Blocks Update

On the Starting Seeds page, I showed how to use a soil block mold for starting seeds. After much experimenting, I have made a few modifications to the process.

  • I no longer try to pack the soil mixture in tighter than I can get by just pressing down several times. I had even tried using blocks of wood to pack it in tighter. While that gave good results, it was pretty tough on the hands, so I went back to the method recommended by the manufacturer. I still try to pack it in as tightly as possible, but only by pressing the mold into the mixture.
  • I no longer use a bucket to press the mold into the mixture – I now use a stainless steel warming tray that I bought from a used restaurant supply store. This is much easier to work with and it allows me to make much better use of the wet soil mixture than I could with the rounded sides of a bucket.
  • I have added galvanized hardware cloth in the bottom of the seed trays. Previously, the blocks would get damaged when I had to move the trays. The stiff, flat bottom that the hardware cloth provides keeps the blocks from bumping into each other.

Hardware cloth lines the bottom of the tray to keep the blocks stabilized when moving the tray. This is a big help in keeping the blocks from being damaged.

The work area. From front to back: water bucket to clean blocker between moldings, stainless steel warming tray where the blocker is packed, seedling tray where blocks are placed when finished.

Packing the growing mixture into the soil blocker.

A garden knife is used to cut away excess from the bottom.

Wipe away excess from the sides using your fingers.

Four soil blocks being extracted from the mold and onto the seed tray.

The soil blocker is rinsed off between uses. Keeping it clean helps make the blocks uniform.

When the blocks have been extracted from the mold, it is not uncommon for part of the block to separate. Use a metal putty knife to gently press the block back into shape.

Use two putty knives together to separate the blocks. They need to have enough air space between them to keep the roots of one block from growing into an adjoining block.