I must admit that I am particularly interested in successful germination because we just sowed our first seedlings in soil blocks a couple of days ago!

It was our first time using soil blocks EVER and it was a bit of a learning curve, but I think we did OK!

This being our first year as market farmers, I am pretty nervous about our seeds germinating successfully, so I thought I would write about it and maybe pick up a few pointers I can apply to help ease my nerves.

Of course, we will be learning from the soil block master, Eliot Coleman author of The New Organic Grower.

OK, so let’s try to set my, and maybe your own fears to rest and learn how to properly seed and achieve germination using soil blocks.

I should note that I am starting this article AFTER we have already made the soil blocks.

You can check out our article here for how to make a blocking mix and this article for how to make a soil block from the blocking mix.

Seeding The Blocks

Each block is formed with an indentation in the top to receive the seed. The soil blocks are usually sown by hand. 

One seed is sown per block.  There is a temptation to sow two, just to be on the safe side, but it is not necessary.

Trust me when I say that the temptation is real. Depending on the size of the seed, it is actually kind of hard to sow just one seed per block. We did our best to only sow one seed, but on the majority of them, there was more than one seed sown.

Germination is excellent in soil blocks because of the ease in which ideal moisture and temperature conditions can be maintained.

The few seeds that don’t germinate are much less of a problem than the labour to thin all those that do.

How To Manually Seed The Blocks

Seeding can be done with the fingers for large seeds.

Finger seeding is also possible for small seeds that have been pelleted.

The small seeds can be most accurately handled by using a small thin stick, a sharpened dowel, a toothpick, or a similar pointed implement.

Stick Method For Seeding

1. Seeds are spread on a dish.
2. The tip of the stick is moistened in water and touched to one seed.
3. The seed adheres to the tip and is moved to the seed indentation on the top of the block and deposited there.

The solid moist block has more friction than the tip of the stick, so the seeds stay on the block.

We did not use this method, although I think it would have been very useful with the tiny lettuce seeds we were sowing. Next time we will give this method a try.

Another technique is to crease one side of a seed packet or use any other V-shaped container and tap out the seeds by striking the container with your fingers or a small stick.

We actually did try using a V-shaped seeder from Johnny Seeds but found that it was not too useful with the tiny lettuce seeds and we ended up finger seeding them instead.

But again, I think using a moistened stick or toothpick would be the best method for small seeds.

Eliot claims that with practice these planting techniques quickly become efficient and precise.

I hope he’s right!

Germination

Eliot never covers the seeds planted in mini blocks. Oxygen is important for high-percentage seed germination. Therefore even a thin covering of soil or potting mix can lower the germination percentage.

If the sowing instructions suggest the seeds need darkness to germinate, cover the flat temporarily with a sheet of black plastic.

Keep the moisture level high during the germination by misting frequently with a fine spray of water.

For the larger seeded crops in the larger blocks, Eliot gets sturdier seedlings if he covers the seeds. He does this by sprinkling a thin layer of potting soil over the top of the blocks.

The third key to a high germination percentage, in addition to air and moisture, is temperature.

The ideal temperature for germination can best be maintained by using a thermostatically controlled soil heating pad under the blocks.

Eliot uses a temperature of 70-75°F (21-24°C) for most crops.

Watering

Blocks are made in a moist condition and need to be kept that way. Their inherent moistness is what makes them such an ideal germination medium.

It is therefore most important that blocks are not allowed to dry out, which can result in a delay to plant growth and difficulty in rewetting.

When blocks are set out on a bench or greenhouse floor, the edge blocks are the ones that are most susceptible to drying.

Since the block has no restricting sides, the plants never sit in too much water. The block itself will take up no more water than it can hold.

To prevent erosion of the block, watering at first should be done gently with a very fine nozzle. If the nozzle is not fine enough, the mini blocks should be misted rather than watered.

Once the plants in blocks are growing, water can be applied through any fine sprinkler.

Extra care and attention to watering is a general rule in successful block germination.

 It will be repaid many times over in the performance of the seedlings.

Potting On

Potting on is the practice of starting seeds in smaller blocks and then setting those blocks into larger blocks for further growth. 

The smaller block easily fits into a matching size hole in a larger block. The mini blocks are usually plotted on to two-inch blocks and those, in turn, to four-inch maxi blocks.

The two-inch blocks are easily planted on using the fingers.

For the mini blocks, some form of transplant tool for lifting the blocks and pressing them into the cavity will be useful. One of the best implements for this job is a flexible artist palette knife. It provides the extra dexterity necessary to handle mini-blocks with speed and efficiency. 

Keep Them Growing

Potting on should be carried out as soon as the seeds have germinated in the mini blocks and before the roots begin growing out of the small cubes.

The less stress seedlings encounter the better.

For ease of moving, the 4-inch blocks can be set on pieces of tile or shallow saucers and moved in that small ‘flat’ as necessary.

Or, if they are set directly on a smooth surface, the best tool for handling them is a heavy-duty kitchen spatula. It is easy to slide it underneath, and the block can then be lifted safely and moved.

For reference, there is as much soil volume in a 4-inch maxi block as there is in a conventional 6-inch pot. 

In Summary

According to Eliot Coleman, the three key factors to ensure successful germination is to maintain:

1. Proper Oxygenation
2. Adequate Watering
3. Ideal Temperature

I know maintaining these ideal conditions is easier said than done, especially for new market farmers like us. I am going to be a nervous wreck until I see some seedlings sprouting up, that’s for sure!

However with practice, persistence, and determination, we will succeed!

If you have any soil block germination tips you would like to share, please leave them in the comments below.

Stay Local,

Kathy & Jon

your friendly neighbourhood growers