METASEQUOIA: As a follow up, if you are looking for another tree consider the Metasequoia glyptostroboides (dawn redwood). It is also a prehistoric Chinese tree.
Until 1945 the dawn redwood was known only in the form of fossils collected by paleobotanists and was thought to have been extinct for perhaps a million years. After it was discovered alive and well in the remote village of Motao-chi in the Chinese province of Szechwan, the Arnold Arboretum of Boston sent a special expedition to the area. The seeds collected were shared with other botanical gardens around the world, and this deciduous conifer is now widely available from nurserymen.
Mature trees in China are broadly conical and grow about 100 feet tall from thick buttressed roots. Presumably they will eventually attain a similar size in this country--young plants grow 3 feet or more a year--making them too tall for the average garden. On a large lawn, however, they can attract attention not only for their history but for their foliage. Soft, bright green needles, about 3/4 inch long, appear in early spring, then turn pinkish brown before falling in the autumn. Brown cones 3/4 inch long ripen each year.
Dawn redwood is hardy to Zone 5. It thrives in full sun in almost any moist soil. Because it tends to continue growing until late in the summer, it should be planted in a location not subject to early frosts-- thus plant on a hillside rather than in a valley. Growth is symmetrical and pruning is not necessary.
GINKGO: Regarding Ginkgo, there are no known forests of ginkgoes, even in China, where Western travelers first found them in the 17th Century growing in temple gardens. These few cultivated trees turned out to be living relics of prehistoric times, among the last survivors of one of the first groups of plants that abandoned spore propagation for the more efficient seed method. The impressions of their ancestors' leaves may be seen in various parts of the world, including the United States, in rocks that are known to be millions of years old. The tree is called maidenhair tree because the 4-inch smooth green leaves resemble those of the maidenhair fern. They are fan-shaped, tough and completely free of insects and diseases, and turn a lovely shade of yellow in fall. The Chinese have another name for the ginkgo that is derived from the shape of its leaves: they call it "the tree with leaves like a duck's foot."
The ginkgo is not the tree for every backyard. One reason is that it eventually reaches a height of up to 80 feet with a spread of 40 feet or more, but another factor of importance is that it needs nearly 20 years to get over the gawky stages of adolescence and develop the broadly spreading branches of maturity. Young trees 8 to 10 feet tall may require 10 to 12 years to reach 20 feet in height. When they are young, ginkgoes are characterized by long ascending branches that develop asymmetrically. Once recommended for urban plantings because it tolerated fumes and dust, the ginkgo has been discovered to be among the first trees damaged by air pollutants.
Nurserymen generally sell only the male trees.
Both are good trees for the home landscape since they have deep roots and other plants such as rhododendrons and azaleas can be planted under them.