The tree spinach is cultivated for its edible leaves. Tastiest when young, the leaves are eaten raw or cooked like spinach.
An easily grown plant, succeeding in most soils but disliking shade. It prefers a moderately fertile soil.
Edible uses
Leaves - cooked. Of excellent quality, they are a spinach substitute. The raw leaves should only be eaten in small quantities - they contain saponins.
Seed - cooked. Ground into a powder and used with wheat or other cereals in making bread etc. The seed is small and fiddly, it should be soaked in water overnight and thoroughly rinsed before it is used in order to remove any saponins.
http://practicalplants.org/wiki/Chenopodium_giganteum