Clay soil clumps together and offers less then adequate drainage. When clay soil dries out it becomes quite compact and hard and often forms an almost impenetrable crust. There is far less air space, making makes it difficult for a tree's roots to work their way through the soil. Clay soil does offer nutrients for species that do not mind often having waterlogged root systems.
The Austrian pine (Pinus nigra) is a fast-growing evergreen that can easily tolerate periods of drought, extreme wind and heat, and endures chilling temperatures to below minus 25 degrees F. Heavy snows pose no danger to its branches. The tree prefers to be planted in full sun and in soil with a pH of 4.0 to 7.0. Sapsucker birds can create holes in the tree in search of food. Deer also enjoy feeding on seedlings, so protection must be offered when the tree is quite small. Austrian pines can easily grow to 100 feet in tall. The tree forms a nice pyramid shape when young. As the tree ages it begins to sport a flat top with large canopied branches. The needles are dark, deep green in appearance.
The river birch (Betula nigra) has been known to grow 90 feet tall, but 50 feet is the normal height. The tree has a brilliant reddish bark that peels in papery curls for a unique appearance. It often is grown as a multi-stemmed specimen. The tree can easily flourish in even heavy clay soil. When young, the river birch requires pruning to prevent drooping branches. Its lifespan is 30 to 40 years and suffers from no major pests. River birches grow near creeks and streams.
The black ash (Fraxinus nigra) grows to a height of 65 to 70 feet. The tree grows well in clay soil that is moisture laden, but does not do well in areas of drought. Black ash grows in a nice, upright habit that is slightly narrow, making it ideal in an area that requires a slender tree. Foliage is a dark green during summer and turns a brilliant gold in the autumn. Leaves can measure up to 10 inches in length with a width of up to 4 inches. Tiny greenish flowers are produced in the spring. The trees bark appears grey, and as the tree ages the bark develops thick plaques. The tree is often grown as a windbreak. It can be grown in partial to full sun. The black ash's ideal pH is 6.0 to 8.0. Extreme winters pose no problem for the black ash.
The tamarack tree (Larix laricina) resembles an evergreen but drops its needles in the wintertime and is considered to be a deciduous conifer. The tree can be grown in areas of heavy clay soil. During the spring and summer the needles of the tree appear a soft green, but as fall approaches they begin to turn a brilliant golden shade before dropping. The tree can withstand extreme winter conditions with ease. It normally will attain a height of 60 feet.