Magnolia acuminata, commonly called the cucumber tree (often spelled as a single word "cucumbertree"), cucumber magnolia or blue magnolia, is one of the largest magnolias, and one of the cold-hardiest. It is a large forest tree of the Eastern United States and Southern Ontario Canada. It is a tree that tends to occur singly as scattered specimens, rather than in groves.
The cucumber tree is native primarily within the Appalachian belt, including the Allegheny Plateau and Cumberland Plateau, up to western Pennsylvania and New York. There are also numerous disconnected outlying populations through much of the southeastern U.S., and a few small populations in SouthernOntario. In Canada, the cucumber tree is listed as an endangered species and is protected under the Canadian Species at Risk Act.
The leaves are deciduous simple and alternate, oval to oblong, 12–25 cm long and 6–12 cm wide, with smooth margins and downy on the underside. They come in two forms, acuminate at both ends, or moderately cordate at the base (these are usually only formed high in the tree).
Unlike most magnolias, the flowers are not showy. They are typically small, yellow-green, and borne high in the tree in April through June. The name cucumber tree comes from the unripe fruit, which is green and often shaped like a small cucumber; the fruit matures to a dark red color and is 6–8 cm long and 4 cm broad, with the individual carpels splitting open to release the bright red seeds, 10-60 per fruit. The ripe fruit is a striking reddish orange color.
Cucumber trees are excellent shade trees for parks and gardens, though they are not recommended for use as street trees. In cultivation, they typically only grow 15–20 m (50–75 feet) tall, although they reach over 30 m (100 feet) in ideal forest situations. They can become quite massive: the United States national (and most likely world) champion in Stark County, Ohio measures more than seven feet (2 m) in diameter (although only 79 ft or 24 m tall) (Wiki). They grow best in deep, moist, well-drained soils that are slightly acidic although they are tolerant of alkaline soils.
They are tricky to transplant due to their coarse, fleshy root system and should be planted shallow and moved in early spring with a good soil ball.