It takes 15 minutes on foot from Myogadani Subway Station and you might need about one hour and half to go around. I visited on January 4th which is the very first opening day of a year.it has a Japanese garden too but basically this is a botanical garden to see may plants, flowers so the Japanese garden itself was not so elegant . Off curse no flowers were seen now but maybe good depending on the season.

With its many species, labeled and explained, this is truly a research and educational garden. In fact, it is the Tokyo University Graduate School of Science Botanical Garden. It was begun in 1684 by the Tokugawa Shogunate as the Koishikawa Medicinal Herb Garden.   There was a laminated English map at the entrance booth, but we were only given a map in Japanese - there were no available English maps for visitors.  We used the Japanese map to get around.  The woman at the ticket booth marked our map for the momiji area and the Japanese garden, but we knew where to look having visited here previously for sakura.  The momiji tunnel was indeed beautiful. We noticed on the English map mention of a "Sweet Potato Monument” so we penciled it into our Japanese map and made sure we found it to photograph it (Not very exciting, but how often do you get to see a Sweet Potato Monument?)  The grounds are large enough that even though there were many other visitors we did not feel that it was overly crowded.  We did have to wait at times for people to move so that we could photograph just the garden. The birders standing still with their long lens cameras, the young couples and families out for a day, and the painting class students sitting in prime spots around the lower pond, all ended up in some of our photos as did the signs, marking significant trees and plants. The garden proved to be a good place to visit for koyo, as it had previously been for sakura.     Visitor tips: Be prepared for a long walk through a residential area to the garden from the station. The grounds are quite extensive so plan on spending a long time there. From the upper garden to the lower pond and Japanese garden requires walking a path down a steep slope. You can also walk down the hill under the trees off the path - this is a shorter and more direct route, but requires attention to your footing. Do not confuse the Koishikawa Botanical Garden with Koishikawa Korakuen near the Tokyo Dome. ¥400 entrance fee when were there, but it now appears to be ¥500