Thinning feels wasteful and is not. You sow a little thick on purpose so enough seeds push through the crust. After a week or two, when seedlings have one or two true leaves, snip extras at the soil line with scissors rather than pulling, which disturbs neighbors. Leave the biggest, healthiest plants at the spacing on the cheat sheet. Seeds are cheap. A thin stand of well-spaced plants almost always outyields a crowded thicket.

What you can transplant vs. compost

Broccoli, cabbage, kale, and their relatives can often be lifted and moved if you need them elsewhere. Beets, carrots, parsnips, cucumbers, melons, and squash generally cannot — their roots do not like the move. Compost those extras, or eat baby greens you cut.

A dense seedbed on purpose

A variation: sow basil thick in a small square under a cold frame or row cover for warmth, then transplant at about 4 inches tall to final spacing. Brassicas are often started the same way under cover to get past flea beetles, which can kill tiny seedlings but not a sturdy transplant. See Pests and Season Extension.