The Cucumber magnolia, also called the Whitebark magnolia, is a big, often multiple-stemmed tree with a loose, spreading crown and a smooth bark that turns from light brown into grey. It is native to east Asia and grows in mountain forests all over Japan. The dark green to purple-brown twigs have grey lenticels and dark purple-brown buds. It is in flower in June. It prefers well-drained soil, and can grow in semi-shade (light woodland) or no shade. It can tolerate atmospheric pollution.The obovate leaf is very large; it can be up to a foot long. On top, the leaf is shiny and fresh green; underneath, the leaves have a silvery or blue white powder (bloom). In early summer, highly scented cream-white flowers appear that can reach 8″ across. The cream-white petals are sometimes greenish or purple red tinged. The stamens are strikingly red at the base. This tree can become a beautiful and striking solitary cultivar with age.
The species is hermaphrodite (has both male and female organs) and is pollinated by beetles. The large flowers have a strong melon scent. They are followed by elongated, purple-red compound receptacles that can look like cucumbers and are 5″ to 7″ long. These fruits contain orange seeds. Both the leaves and the flower buds are considered edible and are boiled and eaten as a vegetable in Japan. The large leaves are used to wrap food in some parts of Japan, or may be dried and grilled with miso, shitake mushrooms, and leeks.
Magnolia hypoleuca can eventually reach a height of 80 feet, depending on the site and climate conditions. In Japan, this tree is cultivated and valued for its light, soft, easily worked timber and its medicinal bark, which is also used in traditional Chinese medicine, where it is known as houpu. The highly aromatic bark contains magnolol and honokiol, two polyphenolic compounds that have demonstrated anti-anxiety and anti-angiogenic properties. Magnolia bark also has been shown to reduce allergic and asthmatic reactions. The bark is stripped from the stems, branches, and roots; cultivated supplies today produce most of the bark for commercial and domestic use.