Ginkgo biloba (also spelled gingko) has become a popular tree and many people are able to recognize it. Its a living fossil that has been around for millions of years. Dinosaurs roamed the ginkgo forests and its been part of Chinese herbalism for centuries. It is unlike any other tree we grow and it has become the symbol of strength, hope and peace.
Several ginkgo stood near the detonation site of the nuclear bomb dropped on Hiroshima. They not only survived the blast, but they fully recovered and are still standing. It is now regarded as a symbol of endurance and vitality.
Its long history and unusual botanical attributes have contributed to a number of myths about Ginkgo biloba.
What is a Ginkgo Biloba?
I won’t go into this in detail – you can find much more information on this plant here.
The ginkgo is an ancient Chinese tree that has populated many parts of the world thanks to human intervention. It is slow growing, but adapts to pollution really well and so it is used frequently as a city tree. Its leaves are quite toxic and so has no serious pests in North America and its quite adaptable to various soil conditions.
It has very unusual leaves that form a fairly open canopy, making it a good selection for a garden. In fall, the leaves turn a bright yellow, making a spectacular display.
Ginkgo are wind pollinated which is not surprising since there was no insect pollination when these trees first evolved.
The gingko is dioecious which means a tree is either male or female. Females produce fruit that contains one large seed. This fruit is best known for the fact that its really stinky and has been described as smelling like canine feces, rancid butter and vomit. This is the only drawback to growing this tree.
If you don’t want a full sized tree, it is available as various miniatures allowing you to pick a ginkgo which grows to your desired height.
It seems as if this tree has more myths than most trees. Here are some claims that I’ll investigate more closely.
- You can sex tress before they are mature
- Ginkgo can change their sex
- Males produce fruit
- Fruit is edible
- Nut is edible
- The fruit contains urushiol, leading to poison ivy
- It is indigenous to North America
- In fall all leaves drop at the same time
- The ginkgo improves memory and thins blood
You Can Sex Ginkgo Before It Fruits
Gingko grown from seed will produce 50% males and 50% females. Because the female fruit stinks so bad, very few want to grow them; they only want males. It has been suggested that you can tell the sex of the tree when it is still young, allowing you to weed out the females.
Although many claim to be able to do this, the science seems quite clear. You can’t tell the difference between males and females until they flower.
I have mentioned their flowers and it is common for people to use that term, but ginkgo are non-flowering Gymnosperms. Traditionally, they have been associated with conifers, but they are more closely related to the Cycads, another ancient species. Ginkgo biloba has now been placed in its own phylum, Ginkgophyta.
Can Ginkgo Change Their Sex?
People complain that the male tree they purchased produced fruits when it matured. This has led to a number of myths. Some believe male plants can produce fruit – they can’t.
Others belief that trees can change sex due to environmental stresses. This is mostly a myth, but there is a nugget of truth here. There are rare documented cases where a male tree has developed a branch or two that produces female flowers. These can be pollinated and produce fruit, but the incidence of this is rare. I found no evidence that a whole tree changed sex.
You can also graft male branches into a female tree to improve fruit production.
“This partial sex-switching may be one of the ways that ginkgo has cheated extinction for so long. ”
Is the Fruit Edible?
There is talk about the fruit being a delicacy in Asian cultures, but I found no evidence of this.
The so-called fruit is not really a fruit, since gymnosperms don’t produce fruit, but it looks a lot like a fruit. It is quite toxic and probably not consumed, at least by humans.
Is the Nut Edible?
Inside the fruit you will find a fairly large nut and this is a popular food source in Asian cultures. Cleaned seeds can be boiled, baked, roasted, or steamed.
The nut contains a number of toxic substances, including 4′-methoxypyridoxine (MPN) and cyanogenic glycosides. These can be consumed in small amounts but they become toxic in larger quantities. For this reason, you should only consume a small number of nuts at any one time.
The Fruit Contains Urushiol
Urushiol is the chemical that produces a rash from touching poison ivy and some people develop a similar-looking rash from ginkgo fruit. This has lead to the conclusion that ginkgo must contain urushiol.
Urushiol is not a single compound, but a mixture of several closely related organic compounds. Although ginkgo contains similar compounds it would be incorrect to say that it contains urushiol or that it causes poison ivy.
It is a good idea to wear gloves when handling the fruit.
What is the Mature Age for Ginkgo?
Some reports suggest that ginkgo can produce fruit once they are 10 years old, but this is probably an exaggeration. Most authorities report that ginkgo reach sexual maturity in 20 to 30 years.
Grafted trees can mature sooner, but these are usually male plants which don’t produce fruit.
Are Ginkgo Native to North America?
Ginkgo biloba, the only species known to still exist, is native to China.
However, fossil records show that other gingko species did grow in North America. So it is not entirely incorrect to consider the gingko to be native to North America.
Do Ginkgo Leaves All Fall at the Same Time?
This is something many people believe and there is some truth here. In fall the leaves all turn yellow and hang on the tree. Then suddenly, one morning you wake up and they are all on the ground, or so it seems.
They don’t all fall at the same time. Leaves fall over a period of several days and some trees can hold on to leaves longer than others. This is all temperature related and the details are still not clear. However, when conditions are right, most of the leaves do fall over a short period of time. A very cold night seems to help coordinate the drop. This fall we had quite warm weather, and my ginkgo dropped leaves over several days.
Ginkgo Medicinal Properties
Ginkgo has been used as medicine for thousands of years and is prescribed for many ailments. A lot of the medicinal value of this tree is attributed to Chinese culture, but that is a bit of a myth. The Chinese did use the ginkgo for medicine, but they only used the nuts. North America uses extracts from the leaves which means that many of the medical claims are not originating from Asian cultures as so often claimed; they are a western phenomena.
Two commonly ascribed benefits are for improving cognition in dementia and for blood thinning.
Ginkgo leaves contain glycosides and and terpenoids which could have an effect on neurotransmitters. This has led to the suggestion that this might improve brain and nerve function.
A 2007 meta-data review concluded that “there is no convincing evidence that Ginkgo biloba is efficacious for dementia and cognitive impairment.”
This is a good example of how myths get started.
One doctor wrote a paper, based on a single anecdotal event with no clinical relevance, and suggested that people assume a “Worst case scenario” and avoid Ginkgo biloba entirely because of a possible danger that it could lead to excessive bleeding.
When Ginkgo is taken with antiplatelet agents such as warfarin (Coumadin) or aspirin, it may cause blood thinning. A meta-analysis of available literature was published in 2005 and suggest that there is “a possible causal association between using ginkgo and bleeding events.” However another meta-analysis published in 2011 concluded that gingko leaf extract did not increase the risk of bleeding.
Buying a Ginkgo
There are a couple of options for growing your own ginkgo.
Growing From Seed
Ginkgo is fairly easy to grow from seed. You can plant seed in fall so they get a cold winter stratification. For more control over the process and higher yields you can remove the seed coat, and provide cycles of 20 C and 30 C, until the seed germinates.
Remember that seedlings are 50% male and 50% female. If you happen to grow a female you might want to get rid of it once it fruits. You could also grow 3 – 4 in one spot, and remove the females as you find them.
Buy a Grafted Male
If you buy a tree, make sure it is a named cultivar so you know which sex you are getting. These will be grafted trees and will produce the type of plant you want.
Buy Grafted Dwarf Cultivars
A normal gingko is quite a large tree and may be too large for some yards. A good alternative is to buy one of the many dwarf cultivars now available. These are available in different shapes and sizes, and you can even get ones with different leaf shapes. There are lots of ginkgo options for smaller gardens.