Etymology
The name Euphorbia unispina is derived from the characteristics of this distinctive species. The genus "Euphorbia" honors Euphorbus, an ancient Greek physician, reflecting the genus's historical use in traditional medicine. The specific epithet "unispina" comes from Latin, where "uni-" means one and "spina" means spine or thorn, highlighting the plant's notable feature of having a singular prominent spine, which distinguishes it from other species within the genus. This naming emphasizes the unique morphological traits that characterize the plant.

Origin
Euphorbia unispina is native to Madagascar, an island known for its remarkable biodiversity and high endemism. The plant is typically found in the southern regions of the island, where it thrives in arid and semi-arid environments characteristic of this area. The unique climate and geological conditions of Madagascar have contributed to the development of Euphorbia unispina's specialized adaptations, allowing it to flourish in rugged terrains and dry habitats.

Description
Euphorbia unispina is a compact succulent shrub, recognized for its distinctive growth habit and architectural form. It exhibits thick, fleshy stems that may display a grayish or green hue, accented by the unique feature of single, prominent spines that appear along the ridge of the stems. The plant often grows in a sculptural, branching pattern, making it an appealing addition for enthusiasts of visually striking succulents. Euphorbia unispina produces small, inconspicuous flowers typical of the Euphorbia family, adding subtle charm to its robust and spiny appearance.

Conservation Status
The conservation status of Euphorbia unispina is influenced by ongoing threats such as habitat destruction and over-collection, common challenges for many endemic species of Madagascar. While specific assessments for this species might vary, efforts to conserve its natural habitat are crucial to prevent further decline. Protecting the biodiversity-rich regions of Madagascar and promoting sustainable practices are essential measures for preserving Euphorbia unispina along with other native flora.

Care
Euphorbia unispina demands conditions that closely replicate its native arid habitat for optimal growth. It requires well-draining soil, such as a cactus or succulent mix, to prevent waterlogging. Position the plant in a location with plenty of sunlight, ideally exposed to bright, indirect light, to mimic its natural environment. Watering should be infrequent, ensuring the soil dries out fully between sessions to prevent root rot. During the dormant winter period, reduce watering further. It is important to protect the plant from severe cold; temperatures should ideally remain above 50°F (10°C). Fertilize sparingly, using a diluted, balanced formula during the active growing season to support its growth. When handling Euphorbia unispina, take care to avoid contact with its sap, which can be irritating to skin and eyes.