Cleistocactus smaragdiflorus aka Firecracker Cactus

Cleistocactus smaragdiflorus is a cactus with a shrub-like form. It belongs to the Cactaceae family. Its native range runs from Bolivia into northwestern Argentina. It grows in forests, such as chaco and yunga woods. Records place it at 1,640–4,920 feet [500–1,500 metres] above sea level. Kew also links it with desert and dry shrubland. The plant grows across a wide range. Some groups grow in protected areas.

This succulent stays green all year and branches from the base. It forms thin stems. They start upright, then arch or creep along the ground. One source gives a height near 3.3 feet [1 metre]. Another reports up to 4.9 feet [1.5 metres]. It also records a spread reaching 19.7 feet [6 metres]. The round stems measure about 0.07–0.10 feet [0.02–0.03 metres] across. Each stem has 12–14 low ribs. Pale brown felt covers the areoles, which bear the spines. Each areole has two groups of spines. There are 10–14 short, needle-like radial spines. Four to six stronger central spines point out from the centre. These range from yellowish to dark brown.

The flowers have narrow tubes with red or pink bases. Their bright green tips give them a clear contrast. The outer flower parts are yellow. The inner parts stay close together. Each flower measures about 0.13–0.16 feet [0.04–0.05 metres] long. The stamens stay inside the flower. The style reaches just beyond them. Round fruits reach about 0.05 feet [0.015 metres] across. People gather the fruit from wild plants and eat it raw.

In gardens, this cactus needs soil that drains very well. LLIFLE calls for a rich growing mix. It says to let the mix dry between waterings. Cold, damp conditions raise the risk of root rot. Dry plants may withstand about 19°F [-7°C], according to LLIFLE. Yet that source says to keep garden plants above freezing. Cold can leave marks on stems, even when plants have protection. High humidity makes frost more risky. Growers can raise new plants from seed or cuttings.

Gardeners grow this species for its form and two-tone flowers. Useful Tropical Plants reports no known hazards or medical uses. That does not prove safety for pets or every plant part. Its account lists the species as Least Concern in 2017. Farming and goat ranching threaten parts of its habitat. Its wide range and large numbers help explain that status.