Here is one example of such a list (for certain months there are variants although cherries are always linked with April!):
January - pine (matsu)
February - plum (ume)
[Plum trees in Osaka Castle's Plum Garden]
March - peach (momo)
April - cherry (sakura)
[Cherry blossoms in Ninnaji Temple, Kyoto]
June - iris (shobu), hydrangea (ajisai)
July - morning glory (asagao)
[Lotus flower in Hokongoin Temple, Kyoto]
September - bushclover (hagi) and other "seven grasses of autumn"
October - chrysanthemum (kiku)
[Maple splendor in Kiyomizu Temple, Kyoto]
November - maples (momiji)
December - camellia (tsubaki)