There are many places in the Tokyo area where one can view azeleas (つつじ, tsutsuji) in bloom. The flowers are usually at their most beautiful in mid-April to mid-May; and at higher elevations, into early June. Below is a list of some of the best locations to see them. 

 
CENTRAL TOKYO

1). Nezu Shrine, Bunkyo Ward:  Central Tokyo’s most famous azelea viewing spot.  Closest stations: Nezu, Todai-mae, and Sendagi

2). Imperial Palace East Garden, Chiyoda Ward, closed Mondays & Fridays.  Enter/Exit from gates: Ote-mon, Hirakawa-mon, or Kitahanebashi-mon

Nine gardens are part of the Tokyo Metropolitan Park Association.  All contain some azeleas, but two are known for them:

3). Rikugien Garden, Bunkyo Ward.  Beside Komagome Station

4). Kyu-Furukawa Garden, Kita Ward.  Closest stations: Nishigahara, Kaminakazato, Komagome

 
OUTER TOKYO

5). Shiofune Kannonji Temple, Ome City. Tokyo’s most beautiful azelea display. Bus from Kabe or Higashi-Ome Station

6). Jindai Botanical Garden, Chofu City.  Buses from these stations: Tsutsujigaoka, Chofu, Mitaka, Kichijoji

7). Showa Kinen Koen, Tachikawa City.  Closest stations: Nishi-Tachikawa, Tachikawa

 
SURROUNDING PREFECTURES

8). Togakuin Temple, Kawasaki, Kanagawa Prefecture.  Bus from Mizunokuchi Station

9). Sankeien, Yokohama, Kanagawa Prefecture.  Azelea bonsai exhibition 5/20-6/3.  Bus from Negishi or Yokohama Station

10). Odakyu Yama-no-Hotel, Hakone, Kanagawa Prefecture.  Bus from Hakone-Yumoto or Moto-Hakone

11). Shimizu Park, Noda, Chiba Prefecture.  Short walk from Shimizukoen Station

12). Godaison Tsutsuji Park, Ogose Town, Saitama Prefecture.  Short walk from Ogose Station 

Looking for more places to view azeleas?  Here is a link to a comprehensive list of Azelea festivals in & around Tokyo (Japanese only)