Lets talk about soil blocking
A little google search later and here we are, intensely overwhelmed, mind blown and thinking screw this soil blocking is far too complex and over complicated – I’ll stick to my stupid plastic pots thanks. I’m going to sift through all that crap online, strip it back and actually show you that soil blocking is the most wonderfully simple organic concept ever, you’ll never look at a plastic pot the same way again.
I’m so excited to bring Ladbrookes Soil blockers to NZ. The soil blockers are genuine Ladbrooke Soil Blockers made in the UK, and brought all the way to New Zealand by me. Let’s start with why I LOVE soil blocking and what it is. If you are already converted and just want the ‘how to’ bit scroll on down. I’ll try to keep it short (*try*)
What is soil blocking?
Essentially the crux of soil blocking is you have your Ladbrooke Soil blocker, stuff it full of soil mix and push out a perfectly sized cube of soil to sow your seeds in - simple.
We have 2 different sizes, the Micro 20 soil blocker – which makes 20 x 2cm blocks - this perfect for starting seeds, especially particularly small seeds. Then we have Mini 4 soil blocker which makes 4 x 5cm blocks. The Mini4 has 3 different inserts depending on what you need. The Mini 4 is perfect for starting bigger seeds, cuttings or potting on from the Micro 20 soil blocker and allowing the seedlings to grow on, establish themselves and harden off before being transplanted into the garden.
The seed insert - for direct sowing small, surface sown seeds, or seeds that required a light covering.
The dowel insert - For larger seeds or seeds that need to be sown 3mm deep, such as those that need darkness to germinate, or cuttings (perfect for dahlia cuttings).
The cube insert - This insert is the exact size of the micro20, which is perfect for when you are ‘potting on’.
Why soil blocking?
Sustainable: It massively reduces your need for hundreds of plastic (pots). You can produce an infinite amount of soil blocks, and all you need is your blocker and some trays to hold the blocks (I’m going to experiment with using plastic tray alternatives this summer). Plastic pots fatigue, break and crack quickly over the years especially with our harsh sun in NZ and need replacing. You won’t ever need to replace your soil blocker.
Saves space: I use the Micro20 for sowing all my tiny light loving seeds, or surface sown seeds (such as snapdragons antirrhinum majus, poppies papaver rhoeas, statice limonium sinuatu etc etc). It means I can sow hundreds of these seeds in only a small space. I can fit them all on my tiny heat mat – impossible if you used plastic pots, unless you had the budget for lots of heat mats. Or the opposite if I’m sowing seeds that need cold stratification I don’t take up too much space in fridge. In saying this I actually start a vast majority of my seeds that don't require any special treatment on the micro20 (such as my veronica veronica longifolia, strawflower helichrysum bracteatum, scabiosa scabiosa atropurpurea etc etc). If I happen to have a few seeds that don't germinate I've not wasted valuable space or resources - just a little 2cm cube of soil.
Prevents transplant shock. Perfect for those plants that hate root disturbance (such as Sweet peas lathyrus odoratus and Zinnias Zinnia Elegans), or any seedling for that matter. The roots are essentially air pruned when they hit the edge of the block, so when transplanted into the ground the roots aren’t suddenly shocked when exposed to the air. When planting out in the garden the entire block is planted so they is no disturbance to the root zone – which massively reduces transplant shock for the seedling. When planted out in their blocks the seedlings don’t miss a beat, seedlings that suffer transplant can be set back, days, weeks or even perish. Think about it how many times have you squeezed and tapped seedlings out of those plastic pots and left the roots flapping in the wind, no wonder they get sulky.
Sold? Thought so. Now onto the simple how to guide.
Cube insert Seed pin Dowel pin
Mini 4 Soil Blocker
Micro 20 soil blocker
Micro 20 soil blocker
How to make soil blocks
Flexitub (or bucket of some kind), soil blocker, trays and takeaway tubs
We start with making our soil mix. Everything we need is either already in our gardens, or readily available at the garden centre – no chickens teeth required here. Seed raising mix alone won’t cut the mustard, as your blocks will crumble, fall apart and be very difficult to handle. They isn’t actually a clear-cut perfect recipe, and I encourage you to experiment. However, in saying that I’ve been on a steep learning curve and made a few mistakes along the way and have settle on this mix, time and time again it makes perfect blocks that my seedlings thrive in.
This is my fail proof mix, and is enough to make approx 40 Mini 4 (5cm) blocks, or an insane amount of Micro20 blocks, scale up or down as required:
12 cups of seed raising mix
12 cups of coconut coir (easily available at Bunnings and Oderings both instore and online)
6 cups of compost (I sieved it if it’s a particularly chunky compost)
3 cups of vermiculite
Now just mix it all up and add water. Do this a little bit at a time, they is nothing more annoying than getting over zealous and ending up with soggy soil. How do you know your mix is ready? I hear you ask. Grab a small handful of the soil mix, if you can squeeze out the water but it holds its shape then the consistency is perfect
Now push your blocker into the soil, all the way until you hit the bottom of whatever tub you are using and wiggle it around – to make it smooth on the bottom, give the top handle a squash to compact the blocks and then push the blocks out into the trays you are using. Repeat. Sow seeds according to the packet.
That’s it! done.
Tips, Mistakes and other stuff
Sowing seeds on the Ladbrooke Micro20: I go for 2 methods when using the micro soil blocker. For small fiddly seeds (ie: poppies Papaver Rhoeas, Rats tail statice Limonium Suworowii, veronica Veronica Longifloria). I just sprinkle as evenly as I can onto the blocks. As the seeds germinate I either thin them out, or re plant the extra seedlings into more soil blocks. If I’m sowing seeds on the more expensive side (such as snapdragons Antirrihinum Majus, stock Matthiola Incana) I use a toothpick or tweezers to place individual seeds on the blocks. Even though stock seeds are easy to handle I still sow them on a micro20, as shortly after germination I place them into the fridge to identify potential double or single plants (not that I cull any – its more out of curiosity).
How do I get perfect blocks with the cube insert? It takes just a few moments, but I highly recommend taking just a little bit of extra time to really push the soil mix into the blocker when using the cube insert. This ensures you get a well-defined cube hole for when you are potting on.
Why are takeaway tubs on the list? Now I know I’ve been scathing of the use of plastic, and I’m about to be a massive hypocrite here – but takeaway tubs are perfect for using as mini greenhouse when using the micro20. They help keep moisture in and massively reduce the risk of the seedlings drying out at crucial point of germination. I just keep washing and reusing them. Long term I hope to replace (and recycle) the takeaway tubs with glass tupperware – but I’ll just have to wait until my budget allows and Briscoes has a sale.
How do I water my blocks? Again, this is something that has been deeply over complicated by the internet. I use my hose pipe on the shower setting and water them as I would any other trays of seedlings. I’ve never had any issues with the integrity of my blocks and them falling apart (as the seedlings grow the roots hold the blocks together). I don’t faff around bottom water or anything. If I have some really delicate freshly potted on seedlings I may use my sprayer for a few days.
Why do you use coconut coir and compost? The coconut coir is perfect for holding the blocks together, with the added bonus of holding lots of moisture. The compost in addition to helping bind the blocks together adds a little bit of extra deliciousness to the mix when the seedlings have grown up beyond the cotyledon stage and need the extra nutrition. If my worm farm is being particularly productive I like to also add up to 3 cups of worm castings into the mix for the same reason I add compost. I absolutely cannot stress enough Do. Not. Use. Peat. Make sure your compost is peat free, and don’t be tempted to use peat moss in lieu of coconut coir. Peat moss is wickedly unsustainable, peat bogs take thousands of years to form and are a wonderful carbon sink. By using peat moss you are supporting the destruction of these unique ecological environments, and actively supporting the release of excess carbon into the atmosphere (ok serious talk over).
Mistakes I’ve made
Using garden soil – in my mind it was perfect, it really bonded the blocks together, fast forward 3-4 weeks it was a terrible terrible idea. Even though I sifted the soil it still harboured weed seeds (which of course germinated). The garden soil also dried out fairly quick and made the blocks quite hard, was difficult to retain moisture, and some of the tinier seedlings struggled to penetrate the soil and failed to thrive.
Adding extra nutrients – In some of my initial mixes I added a few spoonful’s of extra nutrients here and there. Maybe I was a bit over keen, and with some more research small amounts of extra nutrients would be of benefit. But with my ‘beefed out mix’ not long after my seeds germinated, they started turning funny colours or crispy and this was essentially from nutrient burn. Most of the seedlings pulled through but it was touch and go – so approach adding extra stuff with caution.
The initial process of making your soil blocks is more time consuming then just filling trays of seed mix into plugs. However at the other side of the process when it comes to planting out, soil blocks are lot less time consuming then squeezing seedlings out of plug trays.
The initial cost of buying a soil blocker is a lot more then buying plug trays or propagation trays. However think about the long term investment over several growing seasons – not just financially but in your overall seedling health.
When you use the Micro20 you have to be on the ball for potting on and thinning out. Leave them too long and the roots become tangled which defeats the benefits of soil blocking, or lead to stunted growth if left to be root bound. Due to the small nature of the micro20 blocks they can dry out quicker - hence the recommendation for using takeaway tubs.
Ok that didn’t end up so short.
But hey if you have any questions or want advice, as always reach out.
If you read this far - Thank you