According to the index of "Saishin Zenkoku Shokubutsuen Guide" document No 20, the following 5 places are carried.
Musashi Hillside National Government Park Arboretum
Kemigawa Arboretum Faculty of Agriculture, University of Tokyo
Botanical Gardens, Nikko, Faculty of Science, University of Tokyo
Tochigi Prefectural Igashira Park
Hamamatsu City Flower Park
We can of course see maple trees at almost all botanical gardens in Japan.
Above all, there can be seen many species of maples at "Nikko Botanical Garden". And there has been published a booklet "Nikko no Kaede", which is a very nice guide for people who comes in contact with maples for the first time. I also think Nikko is a good place climatically and topographically for maples to live.
I visited "Experimental station for Landscape Plants" in Chiba when I began to be interested in maples after an introduction by Prof. Okano Tokyo University, but though there were planted many kinds of maples, what a pity that I came back home without obtaining satisfying information owing to my ignorance of maples at that time.
"Musashi-Kyuryo National Government Park" is a place where I visited in May '98. There did I observe flowers of acer distylum for the first time, and also enjoyed seeing many kinds of cultivars of maples.
At "Aichi Recreation Forest" are planted about 30 kinds of maples including foreign maples with almost all Prefectural Trees. It's a nice place for families to observe maples.
"Hamamatsu City Flower Park" is located beside Lake Hamana, Kanzanji in the city of Hamamatsu. On maples there are planted many trees of cultivars. It's also wonderful to see the Rose Garden and the Begonia Hothouse.
Koishikawa Botanical Gardens is about 10 minutes by taxi from Suidobashi station.
There are some remarkable maples such as lines of Acer palmatum, many trees of Acer diabolicum, large trees of Acer mono, Acer nikoense and Acer carpinifolium and the like.
Kyoto prefectural Botanical Garden is located along the Kamo river north of Kyoto station, from which it takes about 10minutes by subway. Around the ponds in the garden are ranges of Acer palmatum. We can see some large trees of Acer buergerianum and Acer aidzuense, and many kinds of cultivated maples such as 'Aoshidare' and 'Akashidare' and so on.
It takes about 16 minutes on foot to go to Kanagawa Flower Center Ofuna Botanical Garden from West gate of JR Ofuna station. There are many kinds of cultivated maples. I visited there for observation of 'Wakisakanishiki' cultivated species of Acer morifolium.
It takes 6 minutes on foot to go to Botanical Gardens Faculty of Science Osaka City University from Keihan Kisaichi station. There are many kinds of cultivated maples as well as Japanese natural species of maples such as Acer pictum(mono), japonicum,nipponicum,pycnanthum and the like. I visited there for observation of Acer insulare.