Preheat oven to 350°F (175°C) and line a 12-cup muffin tin with cupcake liners.
Beat butter and sugar until light and fluffy. Add egg and sour cream, mix well.
In a separate bowl, combine flour, baking powder, and salt.
Alternately add dry ingredients and milk to butter mixture, beginning and ending with dry. Stir in vanilla.
Divide batter among liners and bake for 18–20 minutes. Cool completely.
Beat butter for frosting, gradually add sugar and vanilla. Beat until fluffy.
Divide and tint frosting: dark green, light green, peach, and white.
Fill piping bags fitted with appropriate tips. Pipe succulents onto parchment, chill to set.
Spread base frosting on cupcakes. Transfer chilled succulents and finish with piped leaves.