Caesalpinia paraguariensis is a deciduous, unarmed tree that can grow up to 18m (50 ft) tall. It has a short bole and usually branches low on the trunk. When pruned, the branch structure is remarkable. Leaves are dark green, which are bipinnately compound (1) contribute to its frondose crown (2) that can spread up to 10 m (30 ft) wide. The bark of mature tranquility tree is decorative - mottled green and brown, and cream. It is the only member of its genus (formerly Caesalpinia) in South America that lacks spines (1). Flowers are small, bright yellow, papilionaceous and usually clustered in large groups. Plants are known to bloom independently of the season (3), and thereafter they produce smooth oval, woody indehiscent pods that are initially green but ripen to a dark blackish-brown (1).

Caesalpinia paraguariensis is a South American native to the Chaco region of South America, including Argentina, Brazil, Paraguay, and Bolivia. Due to its popularity for forage and lumber uses, as well as its use as a landscape ornamental, it is widely distributed in arid and sub-tropical climates.

Although Caesalpinia paraguariensis is more often used as a lumber or agricultural plant, it has value in being used as an amenity plant in eastern Argentina (1) and in xeriscape landscapes in California, Arizona, and Texas. Propagation is done via seed, and scarification is recommended in order to accelerate germination. Once planted, Caesalpinia paraguariensis grows moderately quickly in full sun, and well-drained soil. Although it is drought- and frost-tolerant (2), Caesalpinia paraguariensis is intolerant of strong alkaline or saline soils (1).

Nearly every aspect of Caesalpinia paraguariensis is useful. The stem bark is anti-inflammatory (5) and has strong antimicrobial activity that is useful for antibacterial purposes (6), and the seeds are poisonous. In addition, in its home distribution Caesalpinia paraguariensis is used for several natural remedies, including to treat venereal diseases, as a blood purifier, to induce abortions, and as an emmenagogue (1). 

This plant has been popularized for foraging and lumber use, and is held in great regard by local inhabitants of its home region (1).  One of the most desirable qualities of Caesalpinia paraguariensis is the wood that it produces, called Brown Ebony, or Guayacan wood, which is popular for its intense hardness and extreme durability (4). Aside from its use as “Brown Ebony” in the lumber industry, the strong wood is also used for external applications including musical instruments, poles, and railway construction (2).

Additionally, Caesalpinia paraguariensis has strong value as a fodder plant for domestic cattle. The fruit, seeds, leaves, and pods are high in nutrients and are harvested (7) - and the bark and pods are additionally used in tannin production (1). Other uses of Caesalpinia paraguariensis include its value in bee foraging, and ink and dye production (7). Additionally, it is cultivated as a landscape plant in arid or semi-arid regions, including Arizona and Texas (3), and commonly included in xeriscape designs. Due to its many economic values, high nutrient content, and dependable fruit crops, Caesalpinia paraguariensis is a very important tree in its native distribution, and is becoming more valued as a landscape plant in Argentina and the United States (1).