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FOSSILS FOR FALL : Two Trees That Have Survived for Millions of Years Now Thrive in Southern California Gardens

December 29, 1985|ROBERT SMAUS | Robert Smaus is the gardening editor of Los Angeles Times Magazine.

About 250 million years ago, big changes were occurring on this planet. The climate was becoming drier, and the swamps that had nurtured the beginnings of life on land were disappearing. Plants that grew on soggy ground--bizarre tree-sized horsetails, club mosses and giant ferns, simple plants that were to become the world's coal deposits--were being replaced by more sophisticated sorts. Many of these plants are still around, including two that have become prized in gardens.

Some of the more amazing of these plants almost didn't make it. For years it was believed that all of the many Metasequoias , the first conifers that dominated the ancient forests even here in Southern California, were extinct. But in a discovery that, for paleobotanists, must have rivaled the finding of King Tut's tomb, a stand of Metasequoias (better known as the dawn redwood) was found in 1944 in a remote section of Sichuan, China. Much like California's sequoias, these trees were the last of their kind, having hidden for ages in mist-shrouded mountains.

Growing side by side, as they do at Descanso Gardens in La Canada-Flintridge, a California redwood ( Sequoia ) and a dawn redwood are difficult to tell apart--until winter. Then the dawn redwood loses its leaves--an oddity in the plant world; it is a deciduous conifer (which is why conifer and evergreen are not synonymous).

In colder climates, the leaves turn a presentable yellow before falling, but in Southern California they turn brown, or bronze at best. In compensation, the new foliage is the most brilliant green, as fresh as spring itself. Fortunately for gardeners, dawn redwoods never reach the heights of California redwoods. Though they grow fast at first, a mature specimen is not much taller than a liquidambar, with about the same spread (both are relatively narrow trees, spreading to about 20 feet).

Our other fossil tree, which was also preserved in China, is the ginkgo. It is almost a conifer, but its large, flat leaves land it in its own family, the Ginkgoaceae , of which it is the sole surviving member. Thought to be extinct in the wild, it apparently survived recent ages in temple gardens.

Fossils of Metasequoias are relatively easy to come by (the one pictured on the previous page is from Judy Owyang's fascinating shop, Fossils / Etc., in West Los Angeles), but ginkgo fossils are rather scarce. We had to borrow ours from newscaster Tritia Toyota, who has loved ginkgoes since her father gave her a leaf to press.

Though the ginkgo is kin to the conifers, its seeds are not housed in cones but are inside fleshy plumlike fruits that can be quite odoriferous once they fall to the ground. As a result, most ginkgoes are grafted male trees that don't produce fruit. Despite the unpleasant smell of the fruit, the seeds inside are a traditional ingredient in several Oriental dishes, including a Japanese custard called Chawan Mushi .

Ginkgoes are among Southern California's more reliable sources of fall color; the leaves turn a brilliant yellow in late November and early December and then make a golden carpet that lasts on the ground for weeks after the tree has become bare. We know of one ginkgo fan who gives his gardener a vacation that coincides with this event, so that the leaves can lay undisturbed in all their golden glory on the bright-green lawn. Press one leaf between the pages of a telephone book and the leaf will retain its color for years.

The ginkgo is an excellent garden tree, tolerant of just about anything. It is painfully slow to get started and appears to grow only inches the first few years, looking awkward all the time. Gardens would probably be full of ginkgoes if the trees didn't require such patience on the part of their keepers at first. In time, ginkgoes become elegant, slightly spreading trees. There is also a stiffly upright variety named Fairmount that is good in tight places. The variety named Autumn Gold is distinguished by its stunning color.

Ginkgoes and dawn redwoods are both excellent lawn trees, tolerating--even appreciating--the constant moisture and not minding at all the grasses that grow at their feet. Because both are bare of leaves in the winter, they do best planted in lawns composed of cool-season grasses, such as bluegrass or fescue. The not-too-dense shade from such trees helps the heat-sensitive grasses through the summer, and the leaves fall at just the right time, letting through the light when the grasses do the bulk of their growing and need the most light.

It is not going too far out on a limb to say that there are no better trees for a lawn, and, to boot, these two have 250 million years of service behind them.

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