Chaya or spinach tree or Tree Spinach (Cnidoscolus chayamansa) is actually about twice as nutritious as spinach. It is a good source of nutrients including protein, calcium, iron, potassium, and vitamin C. It is a fast growing dense shrub, native to Mexico's Yucatan peninsula. It grows to about 6-8 feet tall.
Soil: Tolerates most soil conditions, but might dislike acid. Liming and fertilizing should benefit Chaya. The leaves contain a lot of protein, calcium, and potassium, so the soil must have it for the plant to extract, if it is to be healthy. (Nitrogen to make protein)
Water: well to somewhat well drained. Tolerates brief flooding and droughts
Sun: full is best, tolerates shade
Cold: Can be killed by a hard freeze, but will usually resprout from the roots. Mulch the base to protect it.
Pruning: Unnecessary, but sometimes used to control height. Crowded internal branches can be removed for propagation or aesthetics.
Propagation: Easily propagated by stem cuttings.
Other problems: It can be slow to get going.
Harvesting, storage, and preparation: Most recommendations say not to harvest until the second year, because the plants are slow to establish before they can grow quickly. Our plants seem to take very quickly to our special potting mix. Never harvest more than 50% of the leaves, except from stems cut for propagation. Leaves must be cooked to release cyanide, which evaporates. Apparently aluminum cookware can cause a diarrhea-causing reaction with the cyanide compounds when cooking. We are not sure if this is true. On principle it's wise to cook all fruits and vegetables in non-aluminum pans because of their high acidity.
More photos on Flickr: https://www.flickr.com/search?sort=relevance&text=Cnidoscolus%20chayamansa
More information, including recipes: http://thematrix.sureste.com/cityview/merida2/articulos/chaya.htm
pdf - Chaya Information Sheet (to print out)