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Propagation

This page is about:

Fertilization

The Ginkgo is a gymnosperm, meaning "naked seed", because the seed is not enclosed in a ripened fruit as in flowering plants (angiosperms), but is protected by cones or a fleshy seed coat. Its propagation is unique. Pollination and the development of the sexual phase occur in the first year (April to September in the northern hemisphere). Research  indicates that the embryo is well-developed at the time of dispersal and that the seed coat only contributes to winter dormancy.  After shedding of the seeds the embryo carries on developing according to external temperature: the higher the temperature, the faster the development.

The Ginkgo is (like some conifers and cycads) dioecious, each spring pollen and ovules are produced on separate trees on the short branches among the bases of the young leaves, for the first time after 20-35 years. Occasionally both genders are found on the same tree. It's a dicot. The female tree must be growing in the presence of a male tree to be fertilized. Ginkgo and the cycads are the only living seed-producing plants (spermatophytes) that have motile or free swimming sperm (more info here). The Ginkgo has a unique place because it is the sole living link between the lower and higher plants, between ferns and conifers. This was discovered on September 9, 1896 by Sakugoro Hirase. He found swimming sperms in the seeds of a female tree in the Botanical garden Todaifuzoku in Tokyo. Read more about Hirase on my History-page.

The yellow pollen cones (3-6 on a shoot) on the male tree are hanging looking like catkins, each about 1.2-2.2 cm. On the main axis numerous appendages are attached. The pollen grains are boat-shaped with widely gaping slit. Each bears mostly two pollen sacs (microsporangia) at the tip containing the sperm cells.
 

male pollen

The ovules on the female tree rise from a collar at the base and grow at the tips of straight stalks that bear two (rather often three or more) ovules, each 2.5-3.5 x 1.6-2.2 cm.

 Sometimes the seeds and pollen grow on leaves without stalkes (oha-tsuki = 'attached to leaves' in Japanese), mostly on older trees. These trees also have 'normal' seeds/pollen growing. They are often designated as 'living national treasures' in Japan because of their rarity and specialness (photos here and on my Tree-page).
There is an abundance of seeds on one tree.

Pollen on Ginkgo.

An ovule consists of one integument (the future seed coat) that surrounds a tissue called the nucellus. In this nucellus four megaspore cells are formed. At this time the pollens are released from the pollen sacs of male trees (April-May), they are carried by the wind to the female trees (distance unknown) and land upon a pollination droplet, which is present on the micropyle at the tip of the integument.The drop retracts in the tiny opening and brings the pollen grains into a pollen chamber in the nucellus, where they develop into much branched pollen tubes (gametophytes). One of the cells in the ovule then enlarges, free nuclear divisions follow, cell walls begin to form after that and then two bundles extend throughout the innermost region of the integument, consisting of neck cells and a large egg cell. In the meantime a column of female gametophyte tissue - known as the "tent pole" - elevates between two archegonia and extends towards the pollen chamber.

Video : ovules and spermatozoid of Ginkgo biloba From ScienceNet, Japan

During the months following pollination, the pollen grows big enough to form two motile sperms in the pollen chamber. Sakugoro Hirase observed swimming sperm (motile spermatozoids) for the first time in the seeds of a female Ginkgo tree growing in the Botanical Garden of the University of Tokyo in Japan in 1896. Click here  to see more videos and photos  about the motile Ginkgo sperms.

The basal end of a male gametophyte is suspended in a cavity above the female gematophyte (called the fertilization chamber).
This female gametophyte in the ovule is then green-coloured, filled with starch grains and is unique among seed plants in containing chlorophyll and photosynthesizes. In the pollen tubes the sperm cell of a male gametophyte divides, producing two sperms, each having thousands of flagellae. The  actual fertilization takes place in fall. The pollen chamber and the space around the tentpole unite into a bigger archegonial chamber filled with fluid. The sperms and the contents of the pollen tubes are then released by a rupture of the basal end of the gametophyte (because of its swelling) and swim upwards (the micropyle faces downwards in fall!) into the fertilization chamber filled with fluid (an inner sea). The sperms swim shortly in the liquid and then one of them fuses with the egg nucleus.

The sperm of the Ginkgo has many similarities with that of the Cycad.
Begin September the ovules are still green-coloured.
Shortly after fertilization the growth of the embryo begins, the ovules enlarge tremendously looking like plumlike seeds about 2.5 cm (1 inch) long and this continues after the seeds fall to the ground. The actual fertilization most likely occurs on the tree between 130 and 140 days after pollination.. The embryo grows into the nutritive tissue of the female fertilization chamber (gametophyte). There are 2 cotyledons.

click on picture to enlarge  The seeds fall off the parent tree in fall after the leaves. They are relatively large in comparison to the seeds of most other trees (esp. conifers). A seed at maturity consists of an embryo = endotesta (sometimes 2 or more), nutritive tissue and the seed coat, which is made up of a hard inner layer (sclerotesta with 1 sometimes 3 ribs) and a fleshy, yellow to orange-coloured outer layer = sarcotesta (5-6 mm thick). This outer layer becomes mottled, purplish green and rancid smelling when ripe.

Because of the presence of butyric acid, the fleshy layer produces an odour similar to rancid butter upon decay. Its tissues may cause nausea or skin eruptions (dermatitis) in man. The inner tissues are palatable (gametophyte and embryo). The seed coat also contains small amounts of urushiol, an allergen that  only on contact with the skin is responsible for poison oak and poison ivy contact dermatitis in sensitive people so when gathering the ripe fruits wear rubber gloves. Squeeze out the seeds in a bucket of water, wash them thoroughly and then dry them. After that they look like a large unsplit pistachio nut. (female trees seeds: more info here)
 

video: seeds in September

Ginkgo trees can also reproduce asexually: read the section about the chichi on my Tree-page about this.

The Ginkgo can also be propagated by cuttings (best way to be sure of the sex). Take young or half-ripe wood about 15 cm long during May-July. Put these in a frame  and keep moist. They usually start growing best in their second year. You may also take cuttings of mature wood of the current year's growth. Shoots about 15-30 cm long are taken in December and placed in a frame. They should root in the spring.
More information about treating the cuttings via the propagation-links on my Links-page.

Grafting:  Grafting is often used by nurseries to grow new Ginkgos. Also branches of male trees are grafted onto female trees in order to fertilize them or visa versa; the female trees often produce very good seeds.

Vegetatively propagated Ginkgos seldom have a dominant central leader, because a lateral branch (rooted or grafted) will continue growing in the direction it had when still attached on the parent trunk. Therefore nurseries stimulate the production of vertical shoots by cutting back the trees.

The tree's gender is not easily classified so some say it can be seen by the deepness of the cleft in the leaves (female trees are said to have less deeper incised leaves). Others say a young tree's gender can be seen on female trees which flower 2-3 weeks later than male trees and the female leaves fall later in fall. For instance the old Ginkgo in Utrecht is male and the leaves of the female branch turn yellow later in the season than those of the male tree where the branch is grafted upon (click on photo left for enlargement to see this female branch in fall). Also the female tree tends to have almost horizontal branches. In Chinese literature it is said that seeds marked with two ribs produce female trees and those with three ribs male (although these are more rare). Also the seeds should be sown in such a way that they face each other and those with three ribs should be grown along a waterside...

Dispersal agents    The seedcoat delays germination and attracts animal dispersers once the seeds fall off the tree. In the digestive system of the disperser the seedcoat is removed and the seeds are taken away from the parent tree.

Jeholornis prima, a long-tailed, seed-eating bird  (on Ginkgo tree?), Cretaceous, China.  picture: Chinese Academy of Sciences, Beijing

The scarified seeds are then deposited in droppings, ready for immediate germination (time of germination depending on the climate). Dispersers in the times of the dinosaurs could have been the dinosaurs (probably carrion feeding scavengers), mammals and possibly birds. In the Paleogene two families of primitive Carnivora, the Viverravidae and the Miacidae are potential Ginkgo dispersers. They were relatively small, from the size of a weasel to that of a small cat.

Nowadays different mammals feed on and probably disperse the seeds: the red-bellied squirrel (Callosciurus flavimanus var. ningpoensis) on Tianmu Mountain and the gray squirrel (Sciurus carolinensis) in eastern North America. Also the possum according to an emailer in Australia.
Also carnivores like the masked palm civet (Paguma larvata) in Zhejiang Province, the leopard cat (Felis bengalensis) in Hubei province, China and the raccoon dog  ("hondo-tanuki" = Nyctereutes procyonoides) in Japan.  These carnivores eat whole seeds and deposit intact nuts in their droppings, so maybe the smell of the seedcoat attracts these animals because it resembles the smell of rotting flesh.
Other dispersers are possibly birds, for instance crows, and mice.
This dispersal allows the distribution of the species and transport to some place where there may be less competition for light or other resources. A cache of seeds was found in a tree crotch about 50 m from the nearest source of the seeds, apparently done by birds. In North America seeds without the fleshy outer coat were found beneath various species of trees up to 150 m from the nearest seed-producing Ginkgo.

Growing a Ginkgo from seed

In fall gather the seeds (wear latex gloves). Remove the fleshy coating (gloves!) by placing the seeds in a jar of warm water, crush the coat and squeeze the seed out with your fingers. Watch video (select HD-quality) below:
 

Then rinse the seeds a few times (they must be really very clean!) and let them dry well. Keep them (preferably in slightly moistened sphagnum moss or in a mixture of moist peat and sand -80/20-) in a locked bag or container in the bottom vegetable crisper compartment of your fridge or in a cool, dry place until you plant them. Seeds can also be bought from seed companies, on the internet, nurseries etc. Try to buy from a reputable firm which sells good quality seeds.  The seed can produce a male or female tree!

Stratification:
Although this is not strictly necessary research has proven that germination is better if the seeds experience some cold temperature for 2 months.

Scarification:
Chip the seeds with a sharp knife or make a few swipes with a sharp edged file or use sandpaper to allow moisture being more readily absorbed (imitating the stomach of seed dispersers like the dinosaurs were). Then soak the seeds in cold or lukewarm water for about 24 hours to soften the coat. Seeds that remain floating will most likely not germinate so you can throw them away. Then put the remaining non-floating seeds  into a 10% bleach solution (water/bleach 9:1) for about 10 minutes to protect against fungus, rinse well  2 times after that. Dry them briefly between paper towels.

After my own  research attempts I ended up with these possible stratification methods:
 

If you don't want to stratify the procedure is the same, but then put the closed container or bag in a light spot at room temperature (70-75⁰F/21-24⁰C). Put in pots when a few leaves have grown.
 
 

After stratification move 3-5 seeds into 4-6" pots. The pots must be clean and have at least one drainage hole and best is pots with ribs or slits to get better rootforming. Use fresh soaked sandy potting soil (40% sand with some grit or perlite) (you may spray a fungicide again). Best is sandy loam that drains well. Sowing depth about 0,6"=1,5 cm. Cover lightly with sand. Don't compact, just tap the soil. Put in a cold frame or indoors in a light place, not full sun. Mist daily, water only when necessary. Keep the soil moist, not wet. After germination never let the roots dry out or stand in water. Take care of good air circulation. When the seedlings have grown enough put them outside (transplant in autumn into individual pots) in a shadowy position and fertilize (organic). Put in permanent position after about 2 years.

You may leave your Ginkgo permanently in a pot and treat it more or less like a bonsai. Then you can grow a Ginkgo even on your balcony! More about Ginkgo as a bonsai on my Bonsai-page.
 

  Sowing outside:

In fall sow preferably in a cold frame or unheated greenhouse. Put seeds 2-3" deep and cover with 2 inches of mulch or straw (in autumn), remove this in spring. Then cover the seeds lightly with sand, mulch etc. Best sowing time is March-May when there's longer daylight. Misting is better than watering. Watch out for squirrels, mice etc. Don't sow in the height of summer.

Ginkgo seeds have an irregular germination. Low temperatures (between 2 and 10°C) following fertilization hinder embryo development and delay the germination of outdoor-sown seed until the following spring or summer.
The length of time between pollination and germination under field conditions can vary between 12 and 14 months, depending on local weather conditions.
 
 

. Ginkgo seedling in garden

From an emailer in Japan I got this idea: to get uniform germination bury the seeds 30 cm in autumn, dig them out in spring and sow them. More information about planting can be read on my page about the tree.  Please email me your sowing results and ideas! Below you can read some reactions of readers.

The Ginkgo is listed in the IUCN Red List of Endangered Plants. Although it is cultivated and planted by humans, it is endangered, and at risk for loss of biodiversity because of propagation by cuttings rather than by seed, due to human preference for male trees.

This is the first year I've really cleaned seeds (250+). The smell wasn't as bad as expected, but still bad enough. However, I cleaned the seeds in Sodium Carbonate or washing soda 2 table spoons/1gal water (60ml/4L). Which wipe out about 90% of the smell. I figure that since the smell is caused by acids why not just nutralize the acid with a base and get rid of the smell. It seemed to work. Also, Sodium Bicarbonate which is baking soda should work as well. It's a little weaker though and maybe you should double the rate. I should also note that both of these chemicals are both fungices and very safe to use. You can eat baking soda. My procedure for cleaning is listed below.
1. place everything in a large bucket with washing soda mixture.
2. remove seeds from pulp with hands and place seeds in 8 " plastic flower pot (dump pulp in a safe area).
3. Rince seeds under running water for about 5 minute swirling the seeds around to remove the rest of the pulp.
4. 5 minute dip in fresh washing soda mixture.

My method with most all tree seeds is to keep them in the kitchen refrigerator in a plastic bag of moist sphagnum moss over the winter.  That worked well with Ginkgo seeds. By spring, some of them were already germinating in the bag.

I use peat/perlite mix: take the peat and put it in a container, then pour boiling water over it.  This will get the peat to absorb water and it will kill any fungus spores present. Add the water slowly as to not overwet the mix. Then, once it is cool enough to mix, add perlite. I usually go for a 1:1 mix. You could just as easily go 2:1. Mix it up, and take a handful, make sure you don't get water dripping down your arm when you hold it. Take a couple handfulls, put them in a ziplock bag, add 3-5 seeds, seal, shake it a bit so the seeds are in the mix.  Within a week or 2, the first seedlings will appear. Pot them up as soon as possible, and then reseal the bag and wait for more. Always has worked well for me.

I collected some seeds and started growing them about 3-4 months back.  After carefully reading Cor's directions of course! For a little more than a month, the seeds did nothing. Nothing happened. I thought I had killed them all even though I followed the directions. One day, I woke up and found one little seed have cracked and a tiny root was sticking out! That was so exciting! Since that first seed sprouted, quite a few have followed. That first seedling is about 10 centimeters tall now. And I have 13 more that are growing up everyday. My dream is to plant a Ginkgo forest.

About 100 Ginkgo seeds were planted in milk cartoons in the Ottawa area, Canada, outside under a protective screen of chicken wire. I watered these regularly and 90-95% have germinated. (source: Truscott).

I soak the seeds 2-3 days in water and then put them in a tray on a layer of sand. Then I cover them lightly with sand. I put the tray on a warm and light spot. I check the sand each day and if necessary moisten it again.

I live near Merano, Italy, and collect seeds in January, this way saving the stratification. After washing away the smelly flesh, I soak them in water for 4 days  (in the house,  about 20°). Afterwards I plant them in pots on the windowsill. The windowsill is at a window facing the east. After 6 weeks 90% have grown.

Many of my college texts have the leaves pressed between the pages.  It seems like they all fell off the trees overnight and I simply HAD to pick up the ones that caught my eye!

I have always been fascinated with the Ginkgo and have even grown one from seed when I was living in California. I haven't had much luck sprouting a seed here in Colorado but will continue to try. I think Ginkgo's are probably the best looking ornamental tree on the planet !!!

Although growing up as children, we played and danced in the carpet of yellow leaves each autumn, and spent many a day and night keeping cool under it through many hot summers, it has been only in the last 10 years we actually discovered what a treasure we had in our small suburban backyard.  We only found out its name 10 yrs ago when a friend of mine , who was of Chinese descent spotted the fruit and asked to collect them for cooking,  from there we asked someone from an institute to view our Ginkgo who informed us it was well over 50 yrs old and happily took away seeds and seedlings my mother had collected.

I have a female tree in my yard and the first fall after buying my house a man came and asked if he could pick up the seeds. Not knowing what kind of tree it was I said yes. He now comes every year and is most grateful for the seeds as they are fertile ( male tree down the ally). I asked him what he does with the seeds and it turns out he grows seedlings and sells them in his nursery!  I'm very happy that I can be a part of sharing this tree with the rest of the region. My tree must have hundreds of "children" around the area! After reading your site I'm going to try to grow a few myself. This year ( 2000) has a bumper crop of seeds!!

I have been fascinated by Ginkgos for over 30 years and have had a tree about that long.. Several years ago it produced seeds and now happily I have a number of seedlings. All my friends and relatives beg for a seedling. No seeds last year though. I'm hoping this year will be different. Love Ginkgos!!!!! treasure.

We have just recently purchased a Ginkgo Tree.  The circumstances were very strange.  When my father was in Japan (WWII) he fell in love with the tree, and during my youth he mentioned it several times.  Well as times went by, my father passed.  This year, and believe it or not, on Father's Day I took my mother shopping and we stopped at a small garden/lawn store.  As we entered, right in front of us was a small ( maybe 1 1/2 years  old) Ginkgo Tree. Needless to say we took it home and as of today it is doing very well.

I have not decided if all of this work is worth it, as my family thinks I have gone nuts! They think I should just let the squirrels eat the fruits and nuts or just compost all of them. I really hate to have it all go to waste as I feel fortunate to have this living fossil in my yard.
 

Ginkgo seedlings in their first year

In Mexico city they grow in Chapultepec park, there are 24 ginkgoes aprox., and get fruit every year. In rainy years they produce lots of fruits, in dry years less.

Come early fall you can see the Chinese women with their hooks, benches, and gloves collecting them off the ground in the Garden. My students (6th graders) are doing a project on the gingkos and they are scouting around their neighborhood's for more sightings. And also, as it turns out there are about 8 trees 2 blocks away from my home. One morning I noticed an Asian lady shaking the "seeds" from the tree so I went home and got a jar and gloves to collected some to show my students. And I have directed my students to your website for information.

There is a small slim Ginkgo Tree at the entrance to the Park..Carl Schulz Park..home of Gracie Mansion, New York. Not very tall..but elegant and slender. It roots below and  to the right of the street sign 86th Street and East End Avenue.
It stands alone in its simplicity.
Eight feet if we're lucky. She's doing fine....as I noticed her high branches..were bare. But the others...ahhh, the others filled lush with full fans of dark green ginkgo leaves. I can almost wrap my hand around her singular trunk, so slender. She seems to have be punned twice..long ago.
Such was her beauty I wanted just one leave for myself..but I dared not disturb her. Lucky for me..as I was walking home..I looked down..and there on the street... one perfect ...small leaf!!
Ahhhhh the joy of it!
New York, at the intersection of "East"  86th Street, she would be ..located: south east. First tree, on the line of trees..planted in the pavement before entering the park...surrounded by cobble stones.

My mom gave me a "twig" about 5 years ago and said it was a Gingko tree. I planted it in my backyard, not really serious about it growing-I have 2 big dogs... They chewed on it , dug it up a few times and so on.  I didn't have the heart to just get rid of it, because my mom had passed away 3 years ago, and it was a special reminder of her. (She loved gingkos.)   Well, that tree has really earned its spot in the yard !!  It's now about 10-12 feet tall !!!  The leaves are beautiful. It has thrived. The dogs no longer bother it.