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 Mexico. 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 metres (20 ft) tall, but usually is pruned to approximately 2 metres (6.6 ft) 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.

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