If you liked building sand castles as a kid you're going to LOVE making soil blocks. It's basically the same thing without the threat of having all your work being taken out by a wave or overly waxed beach bully.
I've been making googly eyes at soil block makers for a few years but have always been too cheap and skeptical to buy them. That was until I decided to clean out my basement and discovered enough plastic pots to build a sand castle replica of Manhattan. To scale.
Therefore, this spring I justified the purchase of the block makers by rationalizing anything that could get rid of those pot pyramids was worth it.
And so far so good. At this point I have limited experience with them but I've started seeds in them they've already outperformed plastic cells and pots.
Here's why:
- Storing soil block makers from year to year take up less space than storing plastic pots
- Soil blocks eliminate the need to WASH and disinfect plastic pots because - well, because you don't have them.
- The germination rate seems improved.
- You can fit more seedlings on a tray using soil blocks as opposed to pots.
- Transplanting from a small soil block to a larger one is a BREEZE and doesn't disturb the roots at all.
There are other supposed advantages to using soil blocks, but I haven't got that far along in my experiment to confirm them. Things like the fact that soil blocks are supposed to allow plants to "air prune" their roots as they grow out of the blocks which creates a more robust root system.
I feel like that's probably not going to be the case, but soil blocks WILL stop plants from becoming root bound because there's no plastic interrupting their growth making them twirl around and around looking for somewhere to grow.
SO HOW DO THESE MAGICAL LITTLE SOIL BLOCKERS WORK?
By smashing them into very wet soil and them pushing them out. I can't imagine you need more information than that.
Oh. You do? Alright then.
The soil blocks come in different sizes. Tiny for planting seeds, bigger for growing on seedlings and a BIG 4" soil blocker for making blocks for large plants.
How to Use a Soil Block Maker
What You Need:
-
- My DIY soil block recipe.
- Rubber tub or wood box
- Water
- Soil Blockers (available from Amazon, Lee Valley and Johnny's Select Seed
- Flat trays
- Dump some of your soil blocking dirt into a tub with a flat bottom. Water your soil until it's really wet. Like brownie mixture. Then let it sit for a few hours to absorb.
- Pile your soil so it's around 1.5x the depth of the soil blocks you're making.
- Push the block maker into the soil, packing it down hard so the blocks fill up completely with soil. You might have to twist it or wiggle it to lift it up off the bottom of the tub (it can suction onto the bottom a bit.)
- Check to make sure each of the blocks is filled up then knock off any excess dirt so the blocks are flat and even on the bottom.
- Push the block maker down onto a flat surface and press the handle down until a bit of water oozes out of the bottom of the block maker. This means you've compressed the soil enough and the blocks should hold their shape.
- Once you get that bit of water coming out you can release the soil blocker and lift it up. You might need to jiggle it or help the blocks out. Rinsing the block maker after every use helps with that but ... I mean who is seriously going to rinse it out after every use?
That's IT. You made soil blocks.
- The smaller of the block makers (above) which is for sowing seeds makes 20 blocks at a time and has a little indent on the top where you drop your seed. Push the seed down with the end of a pencil to make sure the seed has good contact with the soil.
- There's NO need to cover the seed unless the packet specifies that the seed needs to germinate in darkness.
- Soil blocks are always watered from underneath. To make sure each block gets the right amount of water leave a pathway between all of your blocks for water to flow. You let the blocks soak in the water until they're saturated and then just tip your tray to dump out the excess water. For small blocks like this it only takes 1-2 minutes of soaking before the blocks are ready for you to dump the excess water.
WHAT?!! HOLY CRAP.
Instead of having to dig out started seeds from their cell packs to transplant them into larger pots, these seed starting blocks just DROP right into the soil blocks that are the next size up.
See?
It's dirt genius.
Nothing gets disturbed. And any plant that's sensitive to transplant shock like those with taproots or the famously pissy loofah plant (yes you can grow your very own loofah sponges because they grow on a vine and not in the sea) will thank you for soil blocks.
Obviously not with words because plants can't talk, but they will thank you by not going into cardiac arrest when you transplant them into their next size up or into the garden. If you're lucky, they'll give you a little wink too.
There's a tiny bit of a learning curve so if you aren't making perfect blocks right out of the gate don't worry about it. You'll get there.
How to Make Soil Blocks
Ditch the plastic pots by making soil blocks.
Materials
- potting soil for blocks
- tub
- water
- flat trays
Tools
- Soil block makers
Instructions
- Dump some of your soil blocking dirt into a tub with a flat bottom. Water your soil until it’s really wet. Like brownie mixture. Then let it sit for a few hours to absorb.
- Pile your soil so it’s around 1.5x the depth of the soil blocks you’re making.
- Push the block maker into the soil, packing it down hard so the blocks fill up completely with soil. You might have to twist it or wiggle it to lift it up off the bottom of the tub (it can suction onto the bottom a bit.)
- Check to make sure each of the blocks is filled up then knock off any excess dirt so the blocks are flat and even on the bottom.
- Push the block maker down onto a flat surface and press the handle down until a bit of water oozes out of the bottom of the block maker. This means you’ve compressed the soil enough and the blocks should hold their shape.
- Once you get that bit of water coming out you can release the soil blocker and lift it up. You might need to jiggle it or help the blocks out. Rinsing the block maker after every use helps with that but … I mean who is seriously going to rinse it out after every use?
Notes
- The smaller of the block makers (above) which is for sowing seeds makes 20 blocks at a time and has a little indent on the top where you drop your seed. Push the seed down with the end of a pencil to make sure the seed has good contact with the soil.
- There’s NO need to cover the seed unless the packet specifies that the seed needs to germinate in darkness.
- Soil blocks are always watered from underneath. To make sure each block gets the right amount of water leave a pathway between all of your blocks for water to flow. You let the blocks soak in the water until they’re saturated and then just tip your tray to dump out the excess water. For small blocks it only takes 1-2 minutes of soaking before the blocks are ready for you to dump the excess water.
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Can you share what type of material the white tray is and where you got it?
I love to see your contents over and over because of your quality of writing
Looking at this for next year. My question is when you move it from the small block into the next size up block do you let it dry out a bit first? How to use one pickup a block of wet soil? Especially given that I'm probably going to use the capillary mats you suggest
I have been using a soil/peat blocker scince 1974 v useful for starting things in
Great idea! We were this close to buying the $170 set. I read some reviews first. Small blocks are best for tiny seeds, then they go into the medium blocks. Large blocks are good for larger seeds. We decided that a medium block would be good to start with and found that Fiskars makes a cheaper version that does medium and small blocks. It only makes one at a time, or 4 small ones. $16 (at Amazon): https://www.fiskars.com/en-us/gardening-and-yard-care/products/food-gardening/soil-block-maker-340120-1001
Can I use purchased "seed starting soil" to make these cubes, Karen? I couldn't find your recipe for the soil.
OK WHAT. Loofah sponges grow on vines and not in the sea?? And I can grow them myself?
Gtfoot I am so doing this. Where do I find loofah seeds? Please and ty!!
I am suddenly craving brownies ....
Yes, that's been happening, lol. ~ karen!
Never heard of! Well I learn something all the time reading your blog! Thanks!!!!
I’ve been using these for a few years now and they’re fantastic. Especially being able to start many more plants per tray vs plastic. I did modify the small one to make a deeper indentation though as the lil divot seamed too shallow.
Curious if you end up using the big one. I never have. 😊
I've been meaning to try these too. Petra from Fruition Seeds also sells them.
I decided to try these this year too! My tomatoes germinated really well and the peppers and eggplants are starting. I added a little bit of unflavored gelatin to the mix to help set the soil as I used my own mix and had no idea how it would work. SO much easier than trays and pots. :-)
HI Karen, I bought some from Lee VAlley right after I saw your first post on it. I LOVE them... it made the whole process of starting seeds more manageable for me... I didn't have to get massess of pots ready right off the bat as they are very compact.
I didn't realize I should be watering from underneath (AHH). They don't look dead, but maybe they are sneakily damping off as i write this.
Thank you for this. My broccoli and tomatoes and some marjoram are looking good.
Excellent! ~karen
Those soil blocks look a little crumbly. Are they crumbly? Can some that you don’t plant in right away be allowed to dry out, saved for a rainy day, so to speak, or will they crumble when handled? Those soil blocks look like the cat’s meow, but I wonder how crumbly they are. Crumbly?
HI Brian. They're at their most crumbly when you first make them. When dry they're very hard. You can make them in advance and then rehydrate them by setting them in a tray with water. ~ karen!
Wow, groovy! Thanks for responding! You get a Gold Star for that! I have long since grown tired of all the plastic pots and starter trays. Some years ago, I made starter pots out of newsprint. I thought it would be a great alternative, but I have found that plants struggle getting through that paper barrier with their roots. Having nothing but soil itself to deal with would be ideal, I think. Will now start my search for a block-making set from here in Sweden.
Thanks for running such a great, informative site.
Whoa, this could be a game-changer for gardening. Kinda spendy for the initial investment, but I'm thinking the cost-benefit analysis is in your favor, especially if you care about soil quality, your carbon footprint, and working with the usually temperamental seed/seedling varieties.
Plus, it's a grown up version of making mud pies. Win!
Thanks for sharing.
Karen,Just a head's up that your link to the soil block molds does NOT bring you to a purchase site. Lee Valley does sell the 1, 2 or 3 part kits, but is not where your link leads to!