Magnolia Acuminata - Yellow Flower - Rare Tropical Plant Tree Seeds (5) You are purchasing 5 of these rare seeds: Magnolia Acuminata - Yellow Flower or Cucumber Magnolia One of the few magnolias which makes a great shade or lawn tree, this specimen needs a large space. Often called the yellow flower or cucumber magnolia, it is very cold hardy. The shape of its immature fruits inspired the nickname "cucumber." Over time, they change from green to red. Its flowers are yellow to yellow-green and slightly fragrant.