Over the past few weeks, I've received several calls on a tree issue in Boise. To make the best decision about any issue, it's wise to get the facts first. The fuss over the removal of a few ginkgo trees from the streets of Boise is one of those half-baked campaigns that comes from too much emotion and not enough research.
It's true that the ginkgo is a revered tree in the Far East and that its lineage makes the dinosaurs look like newcomers. According to fossil records, the family that Ginkgo biloba belongs to, Ginkgoaceae, was widely distributed around the world over 300 million years ago--that was before the Rockies, Alps and Himalayas were even formed. The ginkgo's earliest tree form showed up about 150 million years ago before the first pterodactyl launched its leathery, winged body into the sky. When ancestral ginkgos were making their way around the world, there were no other trees, only ferns.
Darwin called the ginkgo "a living fossil." Ginkgo is in a class all by itself, a class of one. It doesn't fit with the flowering broadleaf trees or the conifers (cone bearing evergreens). Ginkgo is the sole survivor from a whole order of plants that once dominated plant life on the earth.
The unusual leaf shape of this odd tree is one of the reasons gardeners plant ginkgos. The fan-shaped leaves have parallel veins radiating from a central point at the leaf base. The common name for ginkgo is "maidenhair tree."
Ginkgos can be found in the gardens of Buddhist temples in China, Japan and Korea, as well as in many towns throughout the United States. Planting a ginkgo is smart because ginkgo has an advantage over other trees--it evolved long before any leaf-eating insect existed. Consequently, insects that mutilate the leaves of other trees won't even touch a ginkgo. This woody marvel has adapted itself to living with humans. It can withstand air pollution in urban settings where other trees fail. Couple its hardiness and lack of pests with its wonderfully golden fall color, distinctive leaves, pyramidal shape when young and lack of disease problems, and it's no wonder the maidenhair tree has been called "the most distinct and beautiful of all deciduous trees." (A deciduous tree is one that sheds its leaves before winter.)
Another fascinating bit about ginkgo is that it houses the male and female reproductive organs on two different trees. Determining the sex of a young ginkgo tree is difficult, and because the fleshy, plum-like seeds often don't appear till the tree is at least 20 years-old, you might not know you have a female tree until it's too late. The plump seeds of the female tree smell like vomit and can cause skin rashes like poison ivy on some people. For these reasons, and possibly because of their large size, female ginkgo trees are being removed from the streets of Boise.
This doesn't mean that gardeners in the Treasure Valley shouldn't plant this stately relic, which can reach a height of 80 to 130 feet with a spread of up to 40 feet; just choose your location wisely. There are several varieties of ginkgo available, even a smaller growing version called "Tit." You'll find variegated varieties of ginkgo with two-toned striped leaves, a weeping variety called "Pendula" and a wide branching variety called "Horizontalis." For a more columnar shape, try "Princeton Sentry." To make sure you are purchasing a non-fruiting, male tree, select only named clones from a reputable nursery. (Clones are vegetatively reproduced plants started from cuttings or bud grafting.)
With the right care, the ginkgo you plant will outlive you, your kids, your grandkids and your grandkids' children. They can live 1,000 years. The oldest living specimen in the U.S. today is growing in a cemetery in Philadelphia. That old monarch was planted in 1784. Western botanists didn't know the ginkgo existed till 1712. To view fossil remains of the fan-leaved wonders, stop by the Ginkgo Forest State Park in Vantage, Washington near Ellensburg, where petrified ginkgo stumps can be seen.
Ginkgo has long been used as a medicine to treat bronchial complaints, reduce the discoloration of varicose veins, soothe stomach distress and improve blood circulation. That last quality is the reason it is a favorite remedy for headache and migraine sufferers. Today, we hear it hailed mostly as an herb that improves memory and alertness, but it was used for much more in the past. Yes, even the kernel inside the smelly seeds is edible. If you have the room, plant a ginkgo for future generations, but choose a male plant--please!