What causes the stone to split in the peach?

Question

What causes the stone to split in the peach?

Answer 1

The peach is what is called a drupe. This means it has a fleshy or succulent layer over a stony layer (the woody pit or stone hull) so both surround the single seed. The stone is indehiscent (not opening) but able to split open along a line (a furrow) that forms a weak zone structurally. Once the seed is stratified over winter it begins to grow and the seed splits the stony endocarp along the furrow easily. The stone is not supposed to open until it is stratified, passes enough time in the cold, about 12 -14 weeks. However some have furrows that are to deep so split too early. If this tree were wild those seeds would germinate before winter and die. However we do not select trees for their pits nor are they grown from seed dropped on the ground to germinate naturally. Peach and other cultivated trees are nursery grown  as grafted clones on rootstock.

Answer 2

The seed is growing. Simple as that.