In "To Kill a Mockingbird," what kind of tree was the tree in the Radley's yard?

The trees adjacent to the school yard were pecans. Scout tells us that nobody would eat the nuts that fell from the Radley tree because Radley nuts were poisonous.

There are also oak trees. The tree with the knot hole that Boo leaves the presents in is one of two oak trees at the edge of the Radley property. The reputation of the Radley trees extends to these trees as well--Jem chides Scout for having eaten the gum she found in the knot hole saying, "don't you know you are not supposed to even touch the trees over there? You'll get killed if you do."