From Block to Garden

This is the payoff page. Air-pruned roots wait at the block’s edge instead of circling, so a soil-blocked seedling goes into the ground with its whole rootball intact and keeps growing as if nothing happened. Two things make that true: hardening off, and not missing the window.

When is a block ready to transplant?

Look for two to three sets of true leaves and roots visible at the block’s faces — for most crops in a 1.5″ block that’s about four weeks from sowing. There’s no cliff: because the roots aren’t circling, a block can wait up to about six weeks before it truly needs out. But don’t overshoot — past its window the block, not the plant, becomes the limit. Smaller blocks close faster (about three weeks for a 0.9″ block), which is why quick potting-up matters at that size.

How do I harden off seedlings?

Indoors, your seedlings have never met wind or real sun. Acclimate them gradually: a sheltered spot outside for two or three hours the first day, a little longer each day after. Some growers compress this into three or four days; others stretch it to a week or two for tender crops started under lights. Watch the plants — stocky and unbothered means go; pale, floppy, or wind-burned means slow down.

How do I plant a soil block?

Like setting a brick: open a hole the block’s size, set the whole block in level with the soil surface, firm it, and water it in. Nothing to unpot, no roots to tease loose. If you slid blocks together in the tray and roots have knit slightly, separate them cleanly with a knife or a plant label before lifting.

What if a seedling outgrows its block before the garden is ready?

Pot it up. Set the smaller block into a larger block’s oversized dimple and the roots wake up and keep going — no unpotting, no shock. This is the job the Dahlia Blocker was built for: its four oversized cells (1″ to 2″) take a smaller block or a rooted cutting — dahlias, melons, pumpkins, and the slow growers like lisianthus that outrun every standard block.

Why soil-blocked transplants don’t stall

A plug-tray seedling spends its first week in the ground repairing torn, circling roots. A blocked seedling’s roots were already paused at the air boundary, tips intact, pointed outward — planting just removes the boundary. Growers describe it the same way over and over: they barely seem to notice they moved.