Nurture
A chart describes tendencies in a traditional system. It cannot decide health, money, law, marriage or children.
In the classical sources
三曰成形，万物在地中成形，如人在母腹成形也
Third is Taking Form: all things take form within the ground, as a person takes form in the mother's belly.
三命通會 卷二
About this stage
養 is the last stage in the list used here, a fetus being fed and shaped before birth. 五行大義 uses the word 養 itself. 三命提要 calls the same place 成形, taking form, and the quotation comes from that older-style count, so the name differs while the seat in the sequence stays the same.
It sits one step before 長生, and a reader of the full circle sees it as the closing move before a stem comes up again: 戌 for 甲, 丑 for 丙, 辰 for 庚, 未 for 壬. The rough sorting in 三命通會 leaves it among the ordinary stages. That book also says the twelve go round 循环无端, a circle with no end, so last on the list is only a place to stop counting.
Where this text comes from
The order of the twelve stages follows 五行大義 volume 2 and 三命通會 volume 2 on Wikisource. The calculator uses that order for wood, fire, metal and water. Works disagree about earth.
The English name follows common modern usage. The wording here is our own plain summary.