How to master the technique of soil blocking for your home nursery

I GENERALLY RECOMMEND that beginning home gardeners buy their vegetable transplants from a nursery or a local gardener’s plant sale. Germinating and tending delicate young plants can be both challenging and frustrating. I’ve met many would-be gardeners who have declared themselves “black-thumbs” after an overly ambitious home-nursery adventure. The truth is, like anything else, everyone is capable of cultivating a talent for home transplant production; it just takes a little bit of patience and the right equipment.

For the experienced or adventurous gardener, growing transplants at home can be one of the most satisfying parts of the garden journey. It’s a sure way to hone your horticultural chops and nurture an even closer bond to the plants in your garden. It’s incredibly satisfying to grow something from seed in the nursery, plant it out in the garden and watch it thrive.

Most growers start with simple and small-scale nursery setups. It’s common to use nursery trays and pots or reclaimed egg cartons and yogurt containers. Once you get comfortable with propagating plants from seed, you’ll no doubt start looking for new challenges. For those looking for a slightly more advanced and waste-reducing technique, I recommend dabbling in the world of soil blocks.

Soil blocking is a technique primarily used by small-scale farmers, but it is easily adaptable to the home nursery. The general idea is to make a slurry of germination mix and squeeze it into small blocks that hold together without any container. When done properly, you’ll end up with a set of stand-alone cubes that you can sow seeds into and then place directly into the garden when ready.

Soil blocks are great because plant roots will stop growing when they reach the edge of the block. Roots don’t like to be exposed directly to air, and this natural barrier prevents seedlings from becoming root-bound. The soil block technique can ease a seedling’s transition into the garden, since its root tips are hanging out at the edge of the block, ready to start growing again as soon as they’re placed into the garden bed.

You’ll need only one piece of new equipment to get started with soil blocks. Unsurprisingly, it’s called a soil blocker. Once you have a soil blocker, all you need to do is purchase or mix up a germination soil blend, add water and start blocking away. Because the soil blocks have no containers, you’ll want to make them on a tray or in a nursery flat. 

Getting started with soil blocks will take practice, and they are certainly more finicky than a traditional nursery container. Be patient when getting started; it’s inevitable that you’ll have some trial and error getting the soil blend and moisture level just right. Blocks that are too dry or too wet simply won’t hold together or form the right shape, but you’ll know when you get it right.

Use warm water when initially moistening the mix, and make sure it’s completely saturated. The consistency of the soil should be similar to a paste, much wetter than in other applications. This initial wetting will help the ingredients form strong bonds and maintain their shape. When the mix is properly saturated, you’ll be able to easily squeeze water out of the soil by hand. Once the mix is adequately wet, the soil blocker will form it into nice tidy blocks. Dipping the blocker in a bowl of water between each set will help keep the soil from sticking inside the tool. After the blocks are all made up, simply place your seeds into the premade divot on top of the block, and cover with a bit of the germination mix. Like any nursery plants, keep an eye on their moisture level daily, fertilize appropriately and enjoy the ride.