What trees produce both hardwoods and softwoods?

This one requires a bit of explanation.

A hardwood tree has broad leaves--oaks, maples, birches. A softwood tree has needle leaves--pines and firs. Since no tree has both kinds of leaves, no tree can produce both hardwood and softwood.

Now...every tree contains heartwood and sapwood. The sapwood is to the outside and carries the sap from the roots to the leaves. Heartwood is inside the sapwood, and it's more dense because it gives the tree its strength. So, heartwood is harder than sapwood, but it's relative; maple sapwood is very hard compared to poplar heartwood.