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Soil blocking! Something I've been really excited and a little nervous about. It's always a little nerve-wrecking to try something new especially after years of getting used to a certain method that's been working just fine. After all, why fix something when its not broken? However, as I did more research on it, I discovered a lot of great things about it that's more beneficial to my seedlings than what I've been doing for years. So what is soil blocking? and what are the pros and cons?


Soil blocking is a method of creating soil blocks or cubes by using a hand held metal mold that you push down into your soil mix. These metal molds come in various sizes to create different size soil blocks. I have a small one that creates twenty 3/4" size blocks at a time, and also one that creates four 2" blocks. The 3/4" mini blocks fit perfectly into the 2" ones. Simply drop the mini block into the bigger one and the seedling from the mini block will expand their root system throughout the bigger one.  

There are a lot of soil mix recipes for soil blocking that includes coconut coirs, compost, sand, perlite, peat moss, etc. Everyone has their own preferences and materials they have access to. I've always used pre-mixed seed starters so that's what I used and the results were great and worked well for me.

Here is a list of materials I use to create soil blocks:

-Soil blocking molds 3/4" and 2"

-Seed starting soil mix

-shallow trays for the blocks

-Rectangular plastic container to place soil mix in (Storage box with lid)


-Small hand trowel

-Watering can

-Spray bottle


-Plant labels

The first thing I do is sort out my seeds. I use the small 3/4" blocks for smaller seeds like poppies, campanulas, etc. Ones that won't outgrow the blocks fast. The bigger 2" blocks are great for bigger and faster growing seeds like sweetpeas, tomatoes, etc. Once that's sorted, I prepare the soil mix by filling half my plastic container with the mix and adding water to it. The goal is to make the soil wet but not soggy. Too dry and the blocks will crumble, and too wet the soil mix will slide out. The perfect ratio for me is when I see water squirt out a bit on top of the mold when it is pressed down into the soil. After filling my trays with blocks, I sow the seeds, label, add vermiculite, and gently water lightly with spray bottle. 


So what's so great about soil blocking? Seedlings that don't like their roots disturbed perform much better than in typical cell trays. Seedlings in general produce healthier root systems as they are not bound within pots and I noticed they grow much faster and bigger as well. One of the most important thing that made me switch to soil blocking, is how environmentally friendly it is. I no longer need to use or buy anymore plastic pots and cell trays. Another bonus is, I use a lot less soil mix than before and the blocks take up way less space then cell trays so I'm able to start more seeds in the same amount of space. Making these blocks is so much fun! It's very therapeutic and I enjoy every minute of it. 


The initial cost of the soil blocking molds can be a little expensive but they are quite sturdy and well made so its definitely worth it in the long run. The soil blocks can be a little tricky to get right and it takes more time and patience than simply filling cell trays with soil. Watering is not the easiest. I use both a spray bottle and watering can. When the soil blocks are still fresh and seedlings are still very small, I only use the spray bottle to water to avoid breaking off the soil. Once I can see more roots around the blocks, I use the watering can to water on top of the blocks and into the tray to let them soak up the water. When there's a good amount of roots developed, the blocks will less likely to crumble during watering. The soil blocks dry up faster than cell trays so I do find myself watering more frequently. 


Soil blocking. Love it. I'm so glad I gave it a try and this will be my seed starting method every Spring. No more plastic pots and cell trays! Seedlings are happier and healthier and I have fun making the blocks. Definitely a win-win situation. I highly recommend giving soil blocking a try if you haven't started already. 


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