This is what the trees look like, from a seed to a seedling, to a large tree, to a yellow leaf carpet:

 

 

 See above for a photo of the ripe seeds on the tree. 

 

The easiest way to spot the trees is to wait until fall when the leaves turn bright yellow, usually all at the same time. In winter the branches have little stubs like pegs, and in the summer the leaves are characteristic (we actually spotted one on an episode of Sex and the City, where one of the women was walking down a small street). Note that most plants are male. I have never found a female ginkgo. (Correction: I finally found a female ginkgo tree growing near Wilmington on 08/10/03. It has seeds on it, and there other trees nearby, so maybe it will be fertilized. ) (Note from 10/27/03: I have recently found a female growing in a backyard next to an alley in New Castle, near the waterfront park, and also a whole row of mixed female and male trees just north of Wilmington. I will be collecting seeds from this street this year)  It is said that the seed pods smell extremely bad when they fall and begin to ripen, and for this reason most trees are grown by cuttings taken from male plants. I had to order these seeds from a source I found on the internet. The gamble is that you will not know the gender of the tree for about 20 years, so if you are planning ahead and don't want females, stick to store-bought trees.  

I have left these descriptions vague so you will have the fun of finding the trees for yourself.

In Wilmington there are lots of trees. There is a huge one at Wilcastle Center, north of town off of Pennsylvania Avenue. There are several large ones when you go into Rockford Park on Lovering, and there is a entire block on 19th St. near Bancroft Parkway. There are several trees on the East Side of Wilmington, where I bike to work, in front of Bancroft school on Lombard street.

My first try at growing these seeds was not very successful. Out of 60 seeds planted, only 10 or so germinated. Some are continuing to germinate in early August, so the final count might go up. I planted 30 seeds after removing them from the pods and cleaning off any remaining flesh. I planted another 30 after cleaning, and then scarifying the seed with a hacksaw. Neither method was very effective. Some of the seeds just rotted away, while others cracked open and the seeds  rotted from the inside. I hadn't yet found a female tree near me, so I bought these seeds over the Internet. I held them, in the fruit, over the winter in a plastic bag, and cleaned them just before planting in the spring. 

Blossom Nursery sells ginkgo seeds online.

The Ginkgo Pages contain a lot of information about the plant, seeds, and usage.

Not related to trees, a recent article in Scientific American reviews some of the purported health benefits of the herb ginkgo biloba, and has a very nice illustration.