Starting Seeds in Soil Blocks Part 2, Making and Planting the Blocks

Collect your trays for the soil blocks.  I use salvaged  clear plastic containers that salad greens or pastries are sold in. I also use small freezer containers to hold a 20-block set of seeds.  If you will be making large quantities of blocks, cafeteria style trays or nursery trays would be convenient if you have some way to retain moisture in the blocks.

You will also need a sturdy trowel, a drywall mudding blade, and a pair of tongs with flat 1-inch tips.

The tools: drywall knife, mason's trowel and salad tongs

Making the Soil Blocks

Techniques vary, so watch a few videos and try different things if this method doesn't work for you. I work with mix that is dryer than some gardeners recommend, transferring scoops of the soggy mix from my bucket (a salvaged detergent bucket) to an old dishpan as needed.

1.  Make a pile of mix that is deeper than the mold.

   

   Pile of mix with Micro-20 mold

2. Firmly shove the mold into the mix, wiggling it down to the bottom of the pan. Make sure you are not pressing the eject handle.
3. Holding the mold down firmly, press the eject handle to compress the mix more.
4. Repeat steps 2 and 3 a couple of times until you can't compress the block more.
5. To remove the block, don't lift straight up because one or more blocks will fall out. Slide the mold across the bottom of the pan and lift up one side to break the adhesion between mix and pan.
6. Holding the mold upside down, use the trowel to mash as much of the excess mix as possible into the holes.
7. Scrape the base of the mold flat, and scrape off any mix clinging to the outside of the mold.
8. Place the mold flat on the tray where you want the blocks to remain and press firmly on the eject handle to compress the block and squeeze out any excess water. Don't lift up yet, this is just more compression.
9. Finally, slowly press down on the eject handle as you lift the mold. If it all worked, you should have soil blocks on a tray. It it didn't work well, dump the bad blocks back into the mix and try again.

TIP: Rinse the block maker often.

Using the Inserts

 The molds come with various shaped inserts that make the holes for planting seeds.

Micro-20 has permanent bumps.

Micro-20 soil blocks, showing the dimples that keep seeds from rolling off the blocks.

The Mini-4 and Mini-5 molds have 2 sizes of dibbles to make a hole for larger seeds.

The Mini-4 can have 3/4" cubes installed to make holes for potting up seeds from the Micro-20

Micro-20 cube inserted into Mini-4 block

Planting the soil blocks 

This is the tedious part. Label the tray or the bottom of the germination box, not the lid.  Label trays before you start placing the seeds.

1. Dump the seeds into a bowl. 
2. Large seeds can be placed by hand into the holes.
3. For smaller seeds and the Micro-20 blocks, use tweezers to pick up one seed at a time and place it into the dimple or hole in the block. 
4. If the seed germinates best if it is covered, sprinkle a thin layer of sifted coir or dry seed block mix over the seeds or into the hole. 
5. Mist the tray of blocks with a spray of water then cover it to retain moisture.

Pepper seeds in Micro-20 blocks, one per block.
I only had a dozen seeds so I removed the unwanted blocks

TIP: If the seeds are extremely tiny, such as thyme and oregano, mix a pinch of the seeds into a spoonful of dry sand or dry sifted coir.  Drop a pinch of this mix onto each block.

TIP: If the seeds are old and you doubt their germination ability, you may be tempted to plant more than one seed per block just to make sure. Resist the temptation!  Murphy's Law applies to gardening, too.  You will have blocks where both seeds germinated, wasting that seed.

Using inoculums with soil blocks

Some seeds may come with an "inoculum" - bacteria that will help the plant develop its nitrogen collecting and fixing properties.  Mix the packet of inoculum into some finely sifted dry potting mix or coir, then sprinkle this mixture over the soil blocks. Mist it with water to wash the inoculum into the blocks. It will spread on its own.

If you are planting a bazillion of the same seed, mixing the inoculum into the block mix before you hydrate it would save time.

Caring for the soil blocks after planting

Keep the blocks moist by misting them or watering from the bottom by gently pouring water into the bottom of their tray. They will fall apart if the water hits with too much force.

Check them daily and if they start to sprout, move them under the grow lights or into a sunny window.