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Somei-Yoshino cherry tree
The most common variety of cherry blossom tree in Japan (Prunus × yedoensis). Produces pale pink to white flowers and accounts for roughly 80% of cherry trees in Japan.
Name origin
染井 refers to 染井村, a village in what is now 豊島区駒込, 東京. 吉野 refers to 吉野山 in 奈良県, historically famous for cherry blossoms. The variety was bred by nurseries in 染井村 and named after both locations.
Cultural note
染井吉野 is the standard reference tree for Japan's 桜開花予想 (cherry blossom forecast). When news reports say "the cherry blossoms have bloomed," they mean 染井吉野 specifically. All trees of this variety are clones propagated by grafting, so they bloom almost simultaneously in any given area.