Soil blocking is exactly what it says it is, where you make blocks of soil of varying sizes. To do so you use a cool contraption called a soil blocker.
Start with the smallest blocker (depending on the plants you're growing) where you're providing the seeds with just enough soil, space and nutrients to get started.
Once they've poked their heads up and have two or more leaves, the blocks are ready to be upgraded to the next size.
But unlike the usual transplanting methods which can be a bit (or a lot) disruptive to the seedling's root system, this technique is seamless. You simply pop the whole block into the next size block.
This means there's no stress caused to the seedling and the root system can continue on it's own merry way, expanding into the additional space provided.
Another cool thing about this method (there are quite a few) is that there is no chance of the roots getting 'root bound' which is a common occurrence when seedlings are left in containers too long.
Instead, the roots are 'air pruned', which means once they reach the boundary of their soil block, air prunes them from going any further, so they can develop a healthy, naturally-shaped root system.
But let's backtrack a bit to the very start.
To make sure your blocks have good 'form' and don't crumble, you have to get the soil mix bang on. We made a mix up with the rough ratios of three parts worm castings (you can also use good compost), one part sand (river sand) and one part coco peat (coconut fibre).
The worm castings are the 'glue' to the mix making sure the whole thing holds its shape, while the sand provides drainage and air pockets and the coco peat does a brilliant job at holding moisture and nutrients in the block.
The mix needs to look crumbly and when you squeeze it tightly there should only be around one drop of water coming out of it, no more.
We used a great sieve to screen the mix, remove any bulky items and make sure there was good 'fluff' factor. It was made from timber lying around the garden and vermin mesh.
Once the mix is ready, you can get going on your blocking. We used the smallest blockers as we were planting out a whole bunch of tomato seeds (which are tiny and don't need much space).
Other plants may be best to start in some of the larger blocks.
There's a bit of technique involved to make a good 'block'. It requires a firm, yet gentle hand and a bit of caution. But after a few goes you'll have your method sorted and pump them out.
You can plant your blocks directly into a standard tray or make your own. We whipped up a whole bunch of planting flats made from timber and corflute which are easy to transport and stack.
The downside of this design is the lack of airflow which means you can have some fungus growing on the timber. As a result we transferred the blocks into standard trays to increase the air flow factor shortly after.
A little trick is to dunk your soil blocker into a bucket of water in between each 'blocking'. This ensures that the blocks can slide out easily without getting caught on soil bits left behind from last time.
Once your blocks are all laid out you can plant your seeds.
Each block has a little hole in the middle, created automatically when you do the blocking, and designed for the seed to be placed perfectly in there.
Once you've done so you can come back with a dusting of soil mix to cover them up and water them in using a spray bottle/mister.
A couple of weeks later and they're ready to be upgraded to the next size block.
Soil blockers are one of those life-changing tools which can save you bucket-loads of time and provide you with a superior product.
- Allsun Farm: Sell a range of soil blockers