Hoophouse Update: Making your own soil blocks

Since my goal this summer is to raise most of the food we eat, I am currently decorating my house in Early Seedling. Flats of greens here. Tomatoes and peppers there. And most of the seedlings will be thinned and transplanted into larger containers at least once before they go into the ground.

In an earlier post, I discussed how my hoophouse (passive solar greenhouse) allows me to plant earlier than most of my fellow Michiganders, who are wise to wait until all danger of frost is gone. And that means that many of the seedlings for my hot-weather tomatoes and peppers are already outgrowing their tiny cells and need to be transplanted into larger pots right away.

A devoted fan of year-round gardening guru Eliot Coleman, I have been thinking about his suggestion that making your own soil blacks make good gardening and economic sense. I have been using peat pots and “cow pots” made from recycled dung, but that is getting pricey, even though I try to buy a case at a time. So this year, I invested in three brass soil-block makers from Johnny’s (to make 1-inch, 2-1/2-inch and 4-inch soil blocks). I hope that this one-time investment will pay off over time.

The gizmo you see above is the four-inch brass soil-block maker. It is sitting in the plastic potting tray I bought this year as well. I do all my transplanting in the kitchen since I need access to warm water, and the tray really does help cut down on the mess.

I am using a commercial soil-less, organic potting medium to make my blocks this year. I hope to experiment with various potting mixtures in the future, since the soil-less potting medium seems less than ideal. I use warm water to moisten the mixture, to cut down on transplant shock. However, too little water and the pots don’t hold together. Too much and they tend to fall apart. I suspect that a mixture with some soil mixed in will hold together better.

To make the pot, you moisten the medium, pile it high (about twice the height of the soil-block maker), push the gizmo down into the medium and then push the plunger to compress the material into a solid block.

The gizmo makes it easy to transfer the soil block to the lattice-bottom black plastic trays that I also hope to use year to year.

Don’t these tomato plants look happy in their new and much-more-spacious home?

Proponents of soil blocks say that seedlings benefit from growing to size without cramping the roots, since the roots simply stop growing when they reach the air that surrounds the blocks. With peat pots and cow pots, the root hairs tend to curl around inside the pot, making it harder to keep the seedlings well-watered and well-fed.

I will conduct my own experiment this year, since I still have some tomatoes in peat pots and cow pots. Stay tuned for updates.