Soil Blocking

We use soil blocks as a method to reduce the use of single use plastics on the farm. Rather than having to buy single use trays every year we have done a one-time purchase of sturdy, thick plastic trays that will last for years to come.  At the beginning I made some trays out of wood however it took me until nearly the end of time to fabricate them, they were more expensive and started to warp after 2-3 uses. Credit where its due, they did look pretty but for all those reasons, we have now opted for the plastic trays.  We also found that having a tray with a side helped as if laid on a flat surface the blocks on the sides are more prone to dry out. This may be less of an issue for people in cooler climates and with a temp controlled greenhouse but we aren’t that fancy yet here so our unheated hoophouse is subject to more temperature fluctuations. 


A soil block is pretty much what the name implies, that is, a block made out of compressed soil. It serves two purposes as both the growing medium and the container in which produces the seedling transplant. The biggest advantage of soil blocks is their ability to air prune the roots as they reach the sides of the blocks rather than becoming root bound and hindering the growth of the seedling once transplanted out into the field. 


One disadvantage I will note is the time it takes to seed a tray rather than the traditional method. You do get faster the more you practice but it is a time consuming task. We have a really tiny farm so I can afford to spend more time making the soil blocks. I will say you do gain some time back when transplanting as they are very easy to slide out of the tray. 

 How To Make Soil Blocks: 

Soil blockers come in a range of sizes. I prefer the 4cm size blocker and use it for all transplants bar sweet peas and sunflowers in which I use the 5cm soil blocker. 

There are many recipes and information out there pertaining to using a specific soil block mix but I have found this both expensive and time consuming and have found no issues using regular organic seeding starting mix. 

You want to wet the mix so that when you squeeze it a handful of water oozes out. Fill the soil blocker by pressing it into the mix and ensuring water seeps out the top. (Using a back and forth motion has helped me ensures the entire block gets filled and small spaces aren’t missed). Lift the blocker, scrape any excess of the bottom and eject the blocks onto your trays by pressing the handle down. You know you have the right consistency of moisture in your block if you can lift it up and drop it 30cm onto the bench and it still stay in shape. Too dry and it will crumble, too wet and it will splat everywhere. Another note is keeping a bucket of water next to the soil mix tub and rinsing the blocker every 2-3 rotations helps ensure the blockers are evenly filled.


YAY! So now you have made a soil block and now get to do it another 2000 more times! No I rarely get sick of doing it, there is something very satisfying about making those neat little bricks in all the trays, they look like gorgeous, yummy brownies. 

You can now drop your seeds into your blocks. It you attached the built in pins you will have holes ready for you or you can remove the pins and make holes to your suiting. I cover my seeds with vermiculite; I have seen others use regular seeding starting mix, which is a far less expensive option. I prefer vermiculite because it is fantastic at water retention and delivering water to the seeds without oversoaking and/or drying them out. 


That’s it! Keep your blocks waterered and at the optimum temp and in no time you will have gorgeous little seedlings to plant out into the field. This is by far my favourite job on the farm, seeing the greenhouse filled to the brim with future blooms reminds me of why I wanted to have a flower farm in the first place. To me, starting the seeds marks the beginning of spring and the new excitement of starting a new season of beautiful, seasonal flowers. 

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