Happy Dancing Turtle’s Grower Dave starts 10,000+ seeds on campus every year. He grows plants in many ways–using hoop houses, aquaponics, hydroponics and the beautiful traditional outdoor garden beds on Campus. Dave uses soil blocks for his seed starts and he recently shared some of his recipes, tips and tricks that also apply to the home gardener.
Here's a 10-minute video on our garden page that gives an overview of the process. And you can read on for more nitty-gritty details.
Benefits of Soil Blocks
Allow seedlings to “air prune.” Their roots will slow down growing when they feel the air at the edge of the soil block, usually around 20 days from the time of seeding. This tells you it’s time to transplant.
Very little disturbance of roots when transplanting. Major disturbance happens when you “pop” a seedling out of a seed cell. This means with soil blocks, no growing time is lost to seedlings having to recover from transplanting.
No plastic waste from seed cell trays or small seedling pots.
You can create many blocks in a short time with a soil block tool. Each block has ready-made indent for seed.
Dave’s Home Soil Block Recipe
For his growing at home, Dave uses a mixture of:
4 parts peat
2 parts soil/compost.
Add garden lime to raise the P.H. of the peat then add blood meal and bone meal (check amounts recommended on the bag).
Sift both compost and peat to remove sticks or other debris that would get caught in soil block tool.
If concerned about fungal disease (or damping off), sterilize soil by baking in oven (145 degrees internal temp for 30 minutes)
Water mixture thoroughly and allow to sit to absorb water (ideally 24 hours).
Soil Block Tool Sizes
Two-inch–most common size used. Fifty two-inch blocks will fit in a standard size tray.
Four-inch–for larger stature plants such as tomatoes and peppers. Some four-inch tools have indent specially-sized to receive two-inch blocks.
Half-inch–for especially small seeds that just get covered with a dusting of soil (e.g.herbs and many greens)
To purchase the tools, Dave has used garden supply places, such as Johnny's Seeds.
Handling Trays of Soil Blocks
Watch trays for their tendency to dry out. Use a shower-type head to water.
Use plastic covers at least until seeds have sprouted.
Track as roots grow to edge of soil block, indicating it’s time to transplant.
Bonus Recipe Material
Would you like to learn the “professional recipe” Dave uses for making soil blocks for the gardens on campus? In a blog post from 2020, Grower Dave walked us through the steps.
Growing Season Prep for the Hoop Houses
Grower Dave maintains two Hoop Houses, a significant part of the Campus gardens that allow for the growing season to be extended. Getting the Houses ready for the growing season includes some kind of dramatic stuff. Using a gas torch, Grower Dave flamed the beds. This flaming accelerates the thawing of the soil, but even more importantly, it creates biochar which has multiple benefits for the soil.
First, pests who over winter in the mulch can be literally “burned out.” Second, burning last season’s mulch (wood chips and straw) as well as some of the plant growth left in place leaves behind biochar which helps micro-organisms in the soil. “The microbes benefit from the surface area created by the char–it gives them a home,” Dave said.
The biochar also adds carbon and structure to the soil, increases water-holding capacity and has the ability to sequester nutrients for enhanced plant growth. It can also be used for soil and water remediation as it can uptake and hold heavy metals and toxins that may be present in the soil or water.
We feel extra safe with Dave at the torch because he also happens to be a trained firefighter. After flaming the beds, they are flooded which not only puts out the flames, but helps the soil begin to thaw. Once the beds are ready for seeding, spinach, radish, collards and assorted greens will be planted.