A) Elm (Ulmus spp.)
These trees are spread over much of the Northern Hemisphere, inhabiting temperate and tropical-montane regions and South over the Equator into Indonesia. There are approximately 30-40 different species of Elms. Eight of these are native to North America. The Elm tree can tolerate a wide range of soil types and pH levels but must be somewhere that drains well. Elms can grow rapidly to be 40-140 feet tall. The leaves alternate on the branches and are doubly serrated down the edges. They are not perfectly symmetrical and come to a long point at the tip.
Most of the mature elms in Europe or North America have been killed by Dutch elm disease. This is a microfungus that is spread by bark beetles. The fungal spores enter the trees through the wounds caused by the beetles and invade the vascular system of the tree. In order to stop the spread, the tree blocks the flow of sap from the roots to leaves, which slowly kills the tree from the inside out. So far, none of the species of trees in North America or Europe have been found to be resistant to the fungus, though there are several species in Asia that seem to be.
B) Green Ash (Fraximus pennsylvanica)
The Green Ash is a fairly hardy tree that can grow in all kinds of conditions. It prefers damp soils or stream banks but is able to withstand droughts to some degree. It is a quick grower that can reach 50-60 feet tall and the crown (top of the tree) can spread up to 25 feet across. Green Ash are relatively short-lived compared to other trees, living on average 30-50 years. It grows well in full sun and provides excellent shade for whatever is underneath it once it is full grown. The leaves are lance-shaped, medium to dark green. It is native to North America.
The Green Ash is threatened by the emerald ash borer, a beetle from Asia that has killed off many of these trees. The emerald ash borer bores into ash trees, destroying the vascular tissue of trees, cutting off the supply of water and nutrients from the roots to the leaves. The tops of the trees start to die and within 2 years the whole canopy of a tree will be dead.
C) Eastern Cottonwood (Populus deltoids)
This large tree is native to North America, growing from the East coast to the southwest and from Canada to Mexico. It grows 67-130 feet tall and can be up to 6 feet in diameter. The leaves are large, broad, and triangular with jagged edges running up the sides. They have flat stems which causes the slightest breeze to shake them in the trees. The turn a bright yellow in the fall as the temperature becomes cooler and it dries out.
Cottonwoods grow best in bare soil and full sun. They prefer to be where they are near water or damp soil. Their seeds are white and fluffy giving them their names. These seed germinate best along river banks, sandbars, and islands.
D) Common Dogwood (Cornus spp.)
The most common type of Dogwood in this area is the Cornus florida or the cultivated flowering dogwood. The leaves are simple, smooth edged, with curving veins that are easy to see. The flowers are usually tightly clustered without petals themselves but have 4 to 6 white petal-like bracts surrounding them.
Certain species of Dogwoods have edible fruit (though not usually the ones grown around here). They are usually grown as ornamental plants because in bloom, they can be quite beautiful. The wood it tough and highly prized for small items that require a very strong hard wood to produce. The tannins in the bark have also been known to prevent the spread of malaria and have been substituted for quinine, a common malaria drug.