I am interested in learning more about the connection between Buddhism and the art of bonsai.
Photo from doomcraft (http://doomcraft.deviantart.com/art/Bonsai-Zen-10380772)
What are the spiritual links between Buddhism and bonsai?
How was bonsai included in the cultural exchange between China and Japan that accompanied the spread of Buddhism?
How did bonsai become a cultural artform so strongly associated with Japan and not China?
Hello and thank you for your question. I know nothing about bonsai except that many people have them here in Japan. It is not unusual to see them in gardens, under a tarp roof. Especially the elderly like gardening here so it's the perfect hobby for the elderly who don't lack in patience.
You can also see some bonsai exhibitions around the country.
Bonsai and stone gardens have long been associated with Zen. Zen aesthetism is a recreation of the natural world. You can visit many famous zen gardens in Japan, especially Kyoto.
I think the reason bonsai have been associated to Japan is the same that Zen has been associated to Japan: Chan Buddhism predates Zen and Dogen went to study Chan in China.
After the war, a lot of Japanese culture was imported in the West due to the American occupation. Zen and bonsai were some of them.
I'm sure can find a more detailed answer to your question in the following books:
This book is a little pricey but the reviews are so excellent that it's a must have for all true bonsai lovers. It covers all: history, philosophy and modern techniques.
This one is more affordable and, if not as good at the one above, is quite complete also. It is specifically about the relationship between nature and Zen.