The extraordinary Ginkgo is “the Super Star” of landscape trees. This large shade tree with attractive leaves, amazing resiliency, and unique history is a valuable street tree planted in urban landscapes worldwide. Ginkgo biloba is native to southwestern China. The species scientific name “biloba” describes the shape of the distinct leaves, meaning “two lobes.” Its most common English name “Maidenhair Tree” refers to the similarity to the fan-shaped leaflets of the maidenhair fern. Silver Apricot, Duck’s Foot, White Fruit, and Grandfather-Grandchild Tree are additional common names.

Interesting facts

One of the oldest living tree species in the world, known as a living fossil, and has one of the longest botanical pedigrees. Leaves and seeds from these “trees that outlived the dinosaurs” were found in ancient fossil beds.

Ginkgo is the sole survivor of an ancient group of trees, a single species with no living relatives. It is the only member of its genus, which is the only genus in its family, which is the only family in its order, which is the only order in its subclass.

There are about one hundred ginkgo trees in China that are thought to be a thousand years old. However, most ginkgo trees do not live more than a few centuries.

In 1945, six ginkgoes survived the explosion of the atomic bomb at Hiroshima, Japan.

Worldwide cultivation and distribution of ginkgo by humans has helped to ensure ginkgo’s survival, a type of botanical insurance.

Ginkgo trees are either female or male. Female trees produce fruit that fall to the ground in autumn. As the fleshy seed coat decays, it releases a strong, unpleasant odor described as rancid butter or as human vomit, giving ginkgo the nickname “ginkgo stinko.” This powerful stench is due to butyric acid.

Ginkgo nuts are a common ingredient in the cuisines of Korea, Japan, and China. The nuts are rich in protein and starch yet low in fats. However, the nuts are potentially toxic, especially raw.

In the East, the ginkgo seeds are used medicinally. But in the West, standardized ginkgo leaf extracts first appeared in Germany in 1964 with promotion mainly as a memory enhancer supplement.

Our Master Gardener tree list—entitled “Ornamental Trees for Home Gardens and Landscapes,” describes Ginkgo biloba as pyramidal-shaped reaching 40-50 feet with a spread of 25-35 feet. Growth rate is very slow. The grayish brown bark becomes deeply furrowed and textured with age. It is deciduous, meaning it drops all of its leaves in one season. Ginkgo does not survive long in frost-free climates.

The broad, fan-shaped, leathery leaves measure up to 4 inches wide. Light green leaves of spring and summer turn a brilliant golden yellow in fall. Ginkgo is most beautiful just before the leaves quite suddenly—nearly all at once—drop as they carpet the ground below. The leaves are slow to decompose, one reason why they make good fossils, and another reason to let the lovely fallen leaves stay awhile before raking.

The apricot-like fruit is about one-inch long with an inner nut portion surrounded by a fleshy, pale yellow outer covering with a silver sheen. The nut inside resembles a pistachio. There is no easy way to determine if a ginkgo nut will produce a male or female tree. A female tree begins its fruit production around 25 years old. Before then it is impossible tell if it is a female or male tree. Ginkgo can be easily propagated by seed, cuttings, and grafting.

There are more than 220 different documented horticultural ginkgo cultivars. Reputable nurseries usually sell only male trees propagated by cuttings. ‘Mariken’ and ‘Troll’ are dense, 3 feet tall shrubs. ‘Princeton Sentry’ forms a narrow pyramid 50 feet tall and 15-20 feet wide. ‘Saratoga’ has drooping, deeply cleft, triangular leaves with unusual frayed edges reaching about 50 feet. It was introduced by the Saratoga Horticulture Research Foundation in California from a seedling selected in 1975. ‘Sky Tower’ is a small, 20 foot high tree with a compact, narrowly conical habit with shallowly cleft leaves.

There are several variegated leaf cultivars that need afternoon shade to protect the variegation from fading in full afternoon sun. Ginkgo bonsai are in great demand. They have the same dramatic fall color and sudden leaf drop as full-size ginkgo trees.

Care

Plant male trees in full sun fall through spring. Ginkgo trees are quite tolerant of air pollution, diseases, heat, various soil types and conditions. Their leaves are unattractive to pests. Water young trees regularly and mulch, keeping mulch away from the tree trunk. No fertilizer is needed.

The Water Use Classification of Landscape Species (WUCOLS) rates the Ginkgo tree as a “moderate water use” tree. The WUCOLS project was initiated and funded by the Water Use Efficiency Office of the California Cooperative Extension. It provides evaluations of the irrigation needs of over 3,500 plant groups used in California landscapes.

Irregular branch growth is common in young ginkgo trees. Cut back awkward branches. Helpful tips on how to train young trees for structure and form is available on the Master Gardener web site.

Arborists spray the herbicide chlorpropham on female trees to prevent them from seeding, thus avoiding formation of the putrid smelling fruit.

Design tips

In small gardens, ginkgo is best used as a focal point in the landscape with ample room to grow.

These slow-growing trees make great long-lived shade trees. Planting them on the southern or western side of your house shades it in the hot summer yet allows the warm sun through in winter.

Since ginkgo can take a lot of abuse, it has become a widely planted street tree.

Wishing you bright winter days in the garden.

This column is not a news article but the gardening advice and opinion of the writer, and does not reflect the views of the Mid Valley Times newspaper.