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Soil blocks can be made in several different sizes for use with a variety of seed sizes.

Courtesy Meredith Seaver, USU Extension

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Small seeds can be started in tiny soil blocks and then moved up into the dibbled holes of larger blocks once the seedlings have a few true leaves.

Courtesy Meredith Seaver, USU Extension

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Seeds planted in soil blocks can be lightly covered with a bit of dry soil or by pinching the edges of the divots over the seeds.

Courtesy Meredith Seaver, USU Extension

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When it’s time to water seeds or seedlings in soil blocks, use the bottom-watering method by setting the seed tray in a shallow tray of water for a few minutes or by watering gently and carefully around the edges of the seed tray.

Courtesy Meredith Seaver, USU Extension

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Is it worth the trouble to try soil blocking? Does it work well?

Soil blocks have been gaining in popularity for seed starting. Transplants grown in soil blocks can develop a more vigorous root system than those grown in containers, and the plants won’t become root bound because there is a thin gap between the blocks that creates an air barrier the roots won’t cross.

Transplants in soil blocks are also easily transplanted, which reduces the risk of transplant shock. Starting your seeds in soil blocks also reduces plastic waste.

Soil blocks are made by using molds to press seed starting. Soil blocks come in different sizes, depending on your seed starting needs, and the molds can include dibbles to make small holes for seeds or larger square holes for “potting up” smaller blocks. These sturdy molds may cost more than the seed starting pots or cell packs you purchase every year, but you’ll recapture that cost after a few years because you won’t be purchasing pots anymore.

Once you purchase a soil blocker, you need a few other items, most of which you’ll probably find around the house:

• A seed tray or other shallow, flat container to hold the blocks once they’re made.
• An old, putty knife, butter knife or kitchen bench knife, etc., to scrape excess soil from the bottom of mold.
• A basin of water to rinse off any soil that clings to the blocker between uses.
• A large flat-bottomed container of soil at least several inches deep and large enough to easily accommodate your blocker.
• Seed starting mix or planting mix.

To make your soil blocks, first you’ll need to prepare your soil. The soil needs to be very wet, about the consistency of wet cement. Once your soil is ready, firmly push the blocker into the prepared soil several times to fill the blocks, gently compressing the soil. Scrape away excess soil, then push the soil blocks into the seed tray. If the soil blocks don’t hold together, try again, compressing the soil more firmly. Rinse off any soil that clings to the empty blocker and repeat until you have enough blocks. Plant your seeds, covering them lightly with dry medium if needed. Don’t forget to label your varieties!

It may be several days before you need to water you soil blocks, but when you do, use the bottom watering method, as the pressure with watering from above may break apart the soil blocks.

Your transplants are ready for planting or potting up once you see roots at the bottom of your soil blocks.

Tips for hobby greenhouse gardeners

Here are some “gear up and clean up” tips for gardeners who use a hobby greenhouse to start their own transplants in the spring.

• Inspect your greenhouse carefully. You want everything to be in good condition before you start any plants.
• Find and seal any gaps or leaks in the covering, around doors or around vents.
• Check screening for small tears and make sure screen frames and window frames fit tightly.
• Make sure vent openers are working properly.
• Check hoses for cracks or missing washers and make sure any watering cans are clean.
• Get everything clean. Cleaning/sanitizing is most important job before you start using your greenhouse each spring.
• Check your greenhouse floor for weeds, moss, algae or old plant debris. All these things can harbor insects and diseases, so you should clean out everything. Sweep, then scrub if necessary. Giving your greenhouse this fresh start every year is very important! Keeping the floor clean and controlling weeds is also important throughout your greenhouse season.

The other surfaces in your greenhouse should also be cleaned and sanitized. Greenhouses and benches (shelves) may be made of many different materials, but the basic recommendation is to scrub or wipe down benches and walls with plain water to remove any soil, plant debris, algae, etc. There are also products made specifically for cleaning and sanitizing surfaces inside your greenhouse, but you should avoid using most of the household cleaners that you might use inside your home as they may damage greenhouse surfaces or even affect the health of the plants you bring in.

Also, take a few minutes to hose off the outside of the greenhouse. Dust and leaves can settle on the roof of the greenhouse. Washing off the roof will make sure you’re getting the most sunlight possible in your greenhouse.