“Sowed in his garden... and it became a tree”
It is like a mustard seed that a man tossed into his garden. It grew and became a tree, and the birds of the air nested in its branches. (Luke 13:18–19 BSB)
What it sounds like today
Small things grow big: a motivational poster.
The cultural key
'Small as a mustard seed' was a standing proverb for the tiniest imaginable quantity (it is not botanically the smallest seed; the proverb, not botany, is being quoted). The sting is in the ending: 'birds nesting in its branches' echoes Ezekiel 17 and 31 and Daniel 4, where the great tree sheltering the birds is a world empire: Assyria, Babylon. Everyone expected the kingdom as a cedar. Jesus gives them a garden herb, a bush of two or three meters. Luke domesticates the scene, a garden rather than a field, and, like Matthew, lets the shrub grow into 'a tree' to meet the Ezekiel and Daniel imagery halfway. Mark keeps it a garden plant; the joke survives in all three registers.
Recovered meaning
God's empire arrives not as Babylon's towering cedar but as a weedy kitchen-garden shrub: laughably humble, absurdly fast-growing, and somehow still the tree where the nations end up nesting. The imperial imagery is deliberately, comically downsized.