The major Southern trees with opposite leaves are:
Maples, Ashes, Dogwoods, Buckeyes, Catalpa, Paulownia
The following ‘acromonic’ may help you remember this group:
“MAD Dogs and Buckeyed Cats named Paul”
Silver Maple: Silver maple leaves have teeth and are whitish below.
Boxelder: The only maple with compound leaves. Leaves have 3 leafleats, and look like poison ivy leaves.
Striped Maple: An understory maple of the southern Appalachian mountains. Prefers middle elevations. Leaves are shaped like goose feet. Bark has conspicuous stripes.
Mountain Maple: Another understory maple of the southern Appalachians. This maple prefers the highest mountain elevations. Its flower and seed stalks always point up (toward the mountains).
Green Ash: The most common Southern ash. One of the few trees (boxelder also) with leaves that are both opposite and compound. Twig buds are brown fuzzy, bark is spongy.
White Ash: The most common ash of the Appalachian mountains. Also has opposite, compound leaves. Twig buds are not fuzzy, bark is spongy.
Flowering Dogwood: The familiar dogwood of spring with showy white flowers that develop into bright red berries. Mature bark breaks into small square black plates some folks call alligator bark.
Alternate-leaf dogwood: This is the only dogwood with alternate leaves, but since it is a dogwood, we put it here. More common in the mountains than in the Piedmont, this tree has very green trunks and limbs.
Yellow Buckeye: A large canopy tree of the southern Appalachians. Has palmately compound leaves with leaflets radiating from a palm-like center.
Painted Buckeye: A small understory tree of rich mature Piedmont forests. Leaves (like all buckeyes) are palmately compound.
Red Buckeye: Has showy red flowers that humming birds love. A small tree found mostly in the Southern coastal Plain.
Southern Catalpa: A fairly uncommon native tree. Has heart-shaped leaves and very long slender bean-like seed pods. Catalpa worms, a kind of caterpillar, regularly defoliate this tree. Fishermen use the worms for bait.
Royal Paulownia (Princess Tree): An Asian exotic escaped from cultivation, this tree also has heart-shaped leaves. Flowers are purple and showy, and fruit is a roundish capsule. The wood is as excellent for woodworking as that of black walnut.