7 Essential Tips for Using Soil Blocks
Soil blocking is an alternative to planting in plug trays. It replicates the ideal conditions to unlock germination and decreases the amount of time a seedling takes to germinate. Usually 3-5 weeks is all it takes to have healthy seedlings that are 3-5 inches tall and ready to transplant outdoors. Pay attention to seed package planting times and cut 2 weeks off if soil blocking.
I use soil blocks because I am very limited on my growing space (which is on shelves in our lower level). I can plant hundreds of seeds in a small room using soil blocks which I could not do if I used plug trays.
I use soil blocks because I am very limited on my growing space (which is on shelves in our lower level). I can plant hundreds of seeds in a small room using soil blocks which I could not do if I used plug trays.
Each brownie looking square has 20 blocks so that tray (above) holds 80 seeds. As you can see in the picture above, it allows me to squeeze a lot of seedlings in a very small space.
1) The soil mix I use is a combination of dirt, peat moss and nutrient mix. This specific blocking mix is used in place of regular bagged soil because it helps the blocks stay together (regular potting soil will break apart over time). I buy a bag of PROMIX potting soil and a bag of peat moss at Menards and combine them with a package of nutrients and follow the recipe on the package which mentions sifting the compost and the peat moss. My husband made a wood frame that I stapled a 1/4" wire mesh to and use that over a Rubbermaid bin to sift PROMIX potting soil and a bag of peat moss into. It sounds complicated but I really only sift one or two times a planting season.
1) The soil mix I use is a combination of dirt, peat moss and nutrient mix. This specific blocking mix is used in place of regular bagged soil because it helps the blocks stay together (regular potting soil will break apart over time). I buy a bag of PROMIX potting soil and a bag of peat moss at Menards and combine them with a package of nutrients and follow the recipe on the package which mentions sifting the compost and the peat moss. My husband made a wood frame that I stapled a 1/4" wire mesh to and use that over a Rubbermaid bin to sift PROMIX potting soil and a bag of peat moss into. It sounds complicated but I really only sift one or two times a planting season.
Peat moss before sifting and after sifting. Mix 3 parts dry mixture with 1 part water - the mix should stick together when squeezed.
2) Of course, soil blocking requires the use of a soil block tool which I bought through Johnny's here. I use the 20 blocker.
3) When I plant seeds, I like to pour my seeds into a tinfoil pie plate. It does not hold static which makes picking up seeds really easy and it makes the seeds easy to see. I use a wet toothpick to pick the seeds up.
2) Of course, soil blocking requires the use of a soil block tool which I bought through Johnny's here. I use the 20 blocker.
3) When I plant seeds, I like to pour my seeds into a tinfoil pie plate. It does not hold static which makes picking up seeds really easy and it makes the seeds easy to see. I use a wet toothpick to pick the seeds up.
4) Once the blocks have seeds, the trays will get covered with saran and go on heat mats, under grow lights until they start sprouting. A heat mat maintains soil temperature 15-20 degrees above room temperature. You will experience quicker and higher rate of germination when heat is used during the germination stage. Once 50% of the seeds have germinated, the saran comes off and the heat mats are removed.
5) Lights are necessary to replicate a growing day. Set them on a timer to give them 16 hours of light or you will get tall, leggy seedlings. I start my timer at 6am and have them turn off at 10pm. Hang lights as close to the seed trays as you can. I use shop lights from Menards.
6) Water first thing in the morning by spraying with water or pouring water around the edges of the soil blocks. Blocks should be dry when you water but seedlings should not wilted. Dump off any excess water once blocks have soaked up enough. If the soil blocks do not dry out enough in between watering, they will rot.
7) Once the seedlings are 3-5" tall they are ready to be hardened off for a week and planted outside. Hardening off is really important. Putting a seedling out into a full day of sun is like putting a baby in the sun all day - they will burn. Start by putting them out for a half hour on the first day and add an hour each day for a week.
Time to get soil blocking!
Reach out with any questions. I'm happy to help!