I've always wondered: who tended to the apple/pear tree when it was a sapling? Who made sure it grew to the size it did? Clearly not any of the Apple children or even Granny Smith (none of them knew about it until the kids started asking around about their parents). So who else could've known?
Only three other ponies were there when the seeds were planted: Mayor Mare, Burnt Oak, and Chiffon Swirl. I have a feeling that the best friends of Bright Mac and Pear Butter would ensure that if the tree sprouted, they'd work hard to make it grow.
After Bright Mac and Pear Butter's tragic passing, the two of them got together for a stroll down the center of the Pear and Apple farms. They reminisced, both trying not to cry as they'd already wept for several days and were growing despondent, but they soon came across a sight that opened the floodgates of emotion. The apple/pear tree had broken free from the dirt. Against all odds, a pear seed and an apple seed had joined together to create something beautiful.
Burnt Oak and Chiffon Swirl made it their personal goal to protect the tree at all costs, so Burnt Oak planted some sod around it to make grass grow while Chiffon watered it with precision every day. It was their solace, their comfort, and their way of knowing that Bright Mac and Pear Butter would never truly leave them.
It's as if the trees were saying: "We're still here…"