Harrisia tetracantha - Cactus

Harrisia tetracantha, also known as "Moonlight Cactus", is a tree-like cactus native to eastern Bolivia. Valued for its slender silhouette and spectacular nocturnal flowering, it can reach up to 3 metres in height in its natural habitat. Its blue-green to grey-green stems are adorned with long white thorns tipped with brown.

Belonging to the Cactaceae family, Harrisia tetracantha is primarily found in the Bolivian departments of Cochabamba, Chuquisaca, Potosí, Santa Cruz, and Tarija, where it grows in dry forests between 1200 and 2600 metres above sea level. The name "Harrisia" pays tribute to the American botanist William Harris. The species features cylindrical stems with eight rounded, tuberculate ribs. The central thorns, initially brownish, turn white to ashy grey over time, while the four to seven radial thorns are white with brown tips. Though large in the wild, this beautiful cactus will more likely reach 1 to 1.5 metres in height when grown in a conservatory. The flowering of Harrisia tetracantha indoors is rare, as this species typically requires specific conditions to bloom, including mature size and day-night temperature variations. However, with proper care and adequate light exposure, flowering can be encouraged. The ephemeral, pure white flowers measure between 18 and 22 cm long and bloom at night. They wilt by dawn, followed by globose red fruits containing small black seeds.

In a collection of succulents, Harrisia tetracantha pairs harmoniously with other xerophilous plants such as agaves, aloes, or opuntias. In pots, it can be combined with trailing succulents like sedums to create attractive arrangements.