I usually use soil blocks to start my seeds rather than plastic trays (although I use some of those also). Soil blocks have a number of advantages – plus a few disadvantages – over plastic trays:
- Soil blocks are made using the same soil it will be planted in – nothing to buy and stock up on.
- They are made using a very sturdy “soil blocker” that, if well cared for, should last decades – if not a lifetime.
- There is no root disruption when planting, so it can be used with plants that normally do not transplant well.
- “Air pruning” means that the seedlings do not get root bound (where the roots start to coil around the sides of a plastic container). When the roots reach the edge of the soil block, they simply stop growing; they resume growing outward when the soil block is planted.
- The disadvantages are that 1) it takes a bit more effort than simply filling up a plastic tray; 2) although they are surprisingly strong, they will not withstand heavy rain or watering or rough handling; and 3) with more exposed area, they can dry out quickly if you aren’t careful.
(Note: Be sure to see the update regarding this.)
After rinsing in water, the soil blocker is pushed down into the soil mixture.
Push it down firmly several times to pack as much soil into the molds as possible.
Push more soil into the molds using your fingers until it will not take any more. It needs to be a solid block of soil.
Scrape the excess soil away from the soil blocker using an old knife blade or something similar.
Position the mold over a tray or whatever you will be putting them in. Don't try to crowd them too closely.
Set the soil blocker on the tray with the blocks lined up straight.
Push down on the spring-loaded rod while pulling up on the handle. The blocks should come out smoothly.
When the blocks have been released from the mold, you might need to use your fingers to push any loose parts of the block. A bit of loose material on the top is not uncommon.
Two metal putty knives work well for picking up and moving the soil blocks.
The soil blocks have a seed hole molded in (you can change the pins for different size seeds). After adding ONE seed per block, add some vermiculite or perlite to cover the seed.
The seed trays are then placed on a seed warming mat to keep the soil warm.
A clear plastic cover is used to keep the soil blocks from drying out from the seed warming mat. It is best to keep the seeds in the dark at this stage, so the clear plastic covers should be covered with a dark material.
Within a couple of days, the sprouts will appear. Remove the clear cover and place the trays under florescent lights designed for plants. Lots of light is very important at this stage, otherwise they will grow spindly and not have the strength to stand erect.