Soil Blocks - The Best Way to Start Seedlings

5 comments by Luke Marion

I am sure if you have started seedlings, you have used either plastic solo cups, plastic nursery pots, or peat pots. All are good, but what if I told you that for quick growing crops, there is a better, cheaper, and simpler way? There is, soil blocks.

Soil blocks are a method of starting seedlings in which small blocks of soil are formed by hand or with a tool called a soil block maker. To create soil blocks, it is so simple!

How to make soil blocks

First, mix water to your favorite potting soil. I find the best potting soil is one that has a good amount of perlite and vermiculite in it so it doesn't get too muddy, clumpy, or dense. Mix water until it is moist but not soggy. You should be able to squeeze the mix and get some water drops to squeeze out.

Next, grab a tray. I prefer to use a seedling tray with holes for drainage. You will need to water them, and you don't want them sitting in water or they will break down faster. Also, they don't have a lot of strength, so if you need to move them, a tray is very handy. Next, Use a soil block maker to compress the soil mixture into small blocks. It helps if you use a dishpan or bus bin for this, since you will need to smash the soil into the blocks with downward pressure to pack the soil into the block maker squares. This can be a bit messy if it isn't contained, which is where the bin comes in. To release the blocks, most will have a spring action handle that will push the blocks out automatically when you release. You want to do this slowly as to not break the blocks. The blocks should be about the size of a standard seedling cell (1.5 inches square and 1 inch deep). Continue making soil blocks until your tray is filled. 

Lastly, press a seed into the center of each block and make sure to keep the soil blocks in a warm, sunny location and mist them regularly to keep the soil moist. Also, pick seeds that are fast growing. Once you get your soil blocks wet, they will begin to soften and fall apart after a little while. The faster you can move the seedlings the better they work. Once the seedlings have sprouted and grown to a sufficient size, transplant them into the garden or larger pots. 

Why are soil blocks better?

Soil blocks work with a process called air pruning. Air pruning is a technique used to control the growth of plant roots by exposing them to air. This causes the tips of the roots to dry out and die, promoting the growth of new, healthy roots. This is why your soil blocks will not look like some pots do, which is a tangles up mangled up mess of roots at the bottom of the pot all spiraling in one direction. 

Air Pruning

Pic Source: (Julia Walker)


  • jessie

    what gauge steel are these? I was looking at some on Amazon a while back, & they had poor reviews because they were too lightweight, and bent with minimal use. Thanks

  • William Rogers

    Have you ever used the pre-made modules? I think they are peat. I bought a kit years ago. The modules fit into a styrofoam block that fits into a tray and floats which provides water to the bottom of the modules. It comes with a domed cover too.

  • Melissa Olson

    Just wondering, could you do something like this using 2 cupcake tins? ( pressing the bottom of one into another with soil in it) Or does this “pack” it too much?

  • Michael

    You can buy seed trays that have dome lids which helps to keep the moisture in and reduces the requirement for misting.

  • Dee Ziemann

    I would love to watch a video on making soil blocks so I can see the moisture content you are describing. I have a soil block maker but I must have compressed the soil too much because my blocks wouldn’t hold water and my pinto bean and kidney bean seedlings dried out even though, I was watering them with a mist sprayer twice a day. Also, I had very poor germination which I blame on my soil being too dry. If I can get these to work, I would love to be able to grow a legume (other than bush beans) to follow my onions and garlic which I harvest mid July. I just don’t have quite enough days before frost to make this happen. It would be amazing if I could squeeze a couple more weeks grow time by starting my beans earlier in soil blocks.

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