Cnidoscolus aconitifolius

Cnidoscolus aconitifolius, commonly known as chaya, tree spinach, or spinach tree, is a large, fast-growing and leafy perennial shrub that is believed to have originated in the Yucatán Peninsula of southeastern México. The specific epithet, aconitifolius, refers to the plant’s "Aconitum-like leaves"—coincidentally, another well-known dangerous, even deadly, genus of plants. As with most euphorbias, the entire plant contains a caustic, viscous and potentially dangerous white sap which flows readily when any part of the plant is broken, cut or damaged.

The plant can grow to be 6 m tall, but usually is pruned to approximately 2 m for easier leaf harvest. It is a popular leaf vegetable in some regional Mexican and other Central American cuisines, used similarly to cooked Swiss chard or spinach. White, typically unremarkable flowers are borne of a terminal panicle held high above the foliage, superficially resembling the small flowering bracts of similar plants like poinsettia or crown-of-thorns.

The leaves should always be cooked before being eaten, as the raw leaves contain a high amount of toxic hydrocyanic acid, in addition to the irritating sap typical of Euphorbiaceae family members. Care should be taken to avoid getting any raw plant material into one’s mucous membranes; i.e., the sap, juice and hydrocyanic acids should, ideally, never contact one’s mouth, eyes, genitals, nose, inner ears or any otherwise open wound or injury. Varying complications can arise from this, ranging from simple irritation to severe burning pain, temporary blindness (if contact is made with the eyes) and loss of smell or taste (in the nose or mouth). While not recommended to consume raw, some sources state that no more than 2-5 raw leaves can, potentially, be eaten per day. However, to truly be eaten safely, the required cooking time for leaves is 5–15 minutes, with 20 minutes being recommended most often in recipes. Additionally, it should not be cooked in aluminum cookware, due to the “malleable”, soft nature of aluminum and the corrosive nature of this plant’s innate alkaloids.

Taxonomy
Cnidoscolus aconitifolius subsp. aconitifolius is endemic to northern México south to Belize and Guatemala, and is cultivated in other countries, as far south as Perú, while C. aconitifolius subsp. polyanthus (Pax and K.Hoffm.) Breckon is restricted to a small area in western México.

Plants in the Chayamansa group (syn. C. chayamansa) are the most widely cultivated, with their lack of stinging hairs on the leaves. There are four predominant cultivars, based on leaf morphology, notably 'Chayamansa' (the most common), 'Estrella', 'Picuda', and 'Redonda'.

Cultivation
Chaya is easy to grow and it suffers little insect damage. It may be a tender perennial in the United States, but persists in climates such as Florida. It is tolerant of heavy rain and has some drought tolerance. Propagation is normally by woody stem cuttings about 6-12 inches long, as seeds are produced only rarely. Early growth is slow as roots are slow to develop on the cuttings, so leaves are not harvested until the second year. Thereafter, chaya leaves may be harvested continuously so long as no more than 50% of the leaves are removed from the plant, in order to guarantee healthy new plant growth.

A USDA study in Puerto Rico reported that higher yields of greens could be obtained with chaya than any other vegetable they had studied. In another study chaya leaves were found to contain substantially greater amounts of nutrients than spinach leaves.

The numerous white flowers of the plants attract butterflies.

Consumption
Some varieties have stinging hairs and require gloves for harvesting. Cooking destroys the stinging hairs as well as toxins found in the raw plant. Chaya is one of the most productive green vegetables.

Chaya is a good source of protein, vitamins, calcium, and iron; and is also a rich source of antioxidants, however, raw chaya leaves are toxic as they contain a glucoside that can release toxic cyanide. Cooking is essential prior to consumption to inactivate the toxic components. In this, chaya is similar to cassava, which also contains toxic hydrocyanic glycosides and must be cooked before being eaten. Cooking in aluminum utensils can result in a toxic broth, causing diarrhea, so aluminium cookware should be avoided.

Young chaya leaves and the thick, tender stem tips are cut and boiled as a spinach. It is a tasty vegetable and is exceptionally high in protein, calcium, iron, and vitamin A. In fact, levels of chaya leaf nutrients are twofold to threefold greater than any other land-based leafy green vegetable. Chaya leaves have a possible antidiabetic effect.

Traditionally, leaves are immersed and simmered for 20 minutes and then served with oil or butter. Cooking for 20 minutes or more will render the leaves safe to eat. The stock or liquid in which the leaves are cooked may be safe for consumption also, as the cyanide is volatilized as hydrogen cyanide (HCN) during cooking.

Cultivars
There are four well known cultivars, 'Picuda', 'Estrella', 'Chayamansa', and 'Redonda'. Cultivars 'Estrella', 'Redonda', and 'Chayamansa' cannot produce seeds or fruit due to unviable pollen, while cultivar 'Picuda' and other cultivars can. These cultivars do not have many urticating hairs compared to other cultivars and the wild type of the species, therefore they are more present in culinary use.