We usually use the term "graft" to mean that humans have intervened to insert a shoot or bud of one plant onto another -- that's how three-way apple trees ... from a single root system.

But like the iPhone and the Macintosh, the Apple tablet revolves around a core piece of software that can trace its roots ... source tree with everything that goes into the system?

In Fielding Questions, readers also asked about caring for a Wodarz apple tree and what to do about a rhubarb seed stalk.

Gala apple tree branches are attached to a "root stock" that includes the root system and base of the tree. It is the lowest section of the tree that comes into contact with a graft, Peck said.