The Secret to Great Plant Starts — soil blocks, soil blockers, seed starting
Why soil blocks work better than plugs
If you want stronger, healthier transplants, try soil blocks, soil blockers, seed starting as a system. Instead of seedlings sitting in plastic cells and circling their roots, a compacted brick of soil allows roots to air prune at the block edge. That encourages lateral root growth, better use of water and nutrients, and far less transplant shock.
What a soil block does for a seedling
A soil block gives seedlings fresh, compacted medium that they can easily explore. When you pot up into a larger block you do three critical things at once:
- More leaf space — the plant can spread its foliage.
- More root room — roots have a bigger medium to colonize.
- Fresh nutrients — new soil contains fertilizer and compost that replace nutrients leached by regular watering.
Mix and moisture: getting the consistency right
The single biggest factor for success with soil blocks, soil blockers, seed starting is the mix texture. You want a heavily saturated, smearable mix — think thicker cake batter, not cookie batter. Too dry and the blocks crumble. Too soupy and they will not form firm edges.
Use a standard potting mix and consider adding a quart of compost and a small amount of organic fertilizer for a nutrient boost. If you avoid peat, substitute wood pulp, parboiled rice hulls, or other binders to hold the block together.
Forming the block and potting up
Pack the mix firmly into the soil blocker, press out excess water, pull the blocker straight up, and give it a little click. Even if the block crumbles a bit at first, plants quickly settle in and send roots into the new medium. One of the neat advantages is that smaller blocks nest inside larger ones, so potting up is fast and tidy.
Watering and rewetting tips
Soil blocks start out saturated and ready to go, which makes putting them under lights or into a greenhouse simple — no immediate top watering needed. Once established, keep an eye on moisture. Blocks can dry out quickly in summer, and once dry they are hard to rewet from above. Bottom watering or soaking trays are the best methods to rehydrate blocks without washing nutrients away.
Practical workflow: fast and efficient potting
Handling blocks is faster than working with plug trays. You can hold a dozen blocks in your hand and pot up row after row with minimal reaching. That speed combined with stronger plants makes soil blocks, soil blockers, seed starting an excellent approach for small farms, market growers, and home gardeners who want better transplant performance.
Quick recipe and setup checklist
- Base: good quality potting mix
- Amend: ~1 quart compost per batch and a handful of organic fertilizer
- Binder: peat moss or peat alternatives (wood pulp, rice hulls)
- Water: mix until smearable and able to hold a compacted shape
- Tools: soil blocker(s) in the sizes you prefer (mini to larger blocks stack nicely)
FAQ
How do I know if my mix is the right consistency?
Squeeze a handful: excess water should drip slightly but the ball should hold its shape when you let go. Aim for a thicker cake batter texture — smearable but not runny.
Can I make soil blocks without peat?
Yes. Substitute peat with wood pulp, parboiled rice hulls, or other binders that give structure. The key is a component that helps the block hold together when compacted.
What's the best way to rewet dry blocks?
Bottom watering or tray soaking is the most effective. Top watering can wash nutrients away and may not penetrate a fully dried block evenly.
When should I pot up my seedlings?
Pot up when roots begin to show at the bottom of the block or when the plant needs more leaf and root room. Potting up refreshes nutrients and reduces the nutrient loss that happens with repeated top watering.
Final notes
Switching to soil blocks, soil blockers, seed starting changes how plants develop. The air pruning, efficient nutrient use, and easy potting up lead to more resilient transplants and less shock at field planting. Try a small batch, tune your mix and moisture, and you will likely see stronger starts in the next season.