Matucana madisoniorum

Matucana madisoniorum is a small cactus from northern Peru. It belongs to the cactus family, Cactaceae. Its native range lies in the country's Amazonas region. There, it grows in dry forest with a seasonally dry tropical climate. Records place it near 1,312 feet [400 metres] above sea level. Its known wild range covers no more than 16 square kilometres. Older names include Borzicactus madisoniorum and Submatucana madisoniorum.

Most plants grow as one rounded stem, though older plants may form clumps. The stem starts low and broad, then lengthens with age. It reaches about 0.49 feet [0.15 metres] tall. Its width reaches about 0.33 feet [0.10 metres]. The skin has a rough surface and a blue-green or grey-green cast. Ribs give the body its shape. Plants without spines can look much like peyote. That likeness concerns their shape, not evidence of shared uses.

Spines vary a great deal within this species. Some plants have almost none; others carry many. A single stem can also have both bare and spiny patches. Young seedlings bear a dense coat of long, curved spines. Those from lower sites tend to shed their spines as they mature. Plants from higher sites tend to keep them. These patterns are not fixed rules for every plant. A bare plant can produce spiny offsets or an occasional spine.

Flowers grow from new areoles at the top of the stem. Their bright orange-red colour contrasts with the duller body. Each flower is zygomorphic and tends to lean sideways. Flowers span about 0.11 feet [0.035 metres] across. Most reach 0.16–0.23 feet [0.05–0.07 metres] long. Some reach 0.33 feet [0.10 metres]. The buds begin as small, woolly grey-white balls. Plants can bloom in several waves during summer. Suitable conditions may extend flowering through much of the year. The dry fruits are delicate and split along their sides. This leaves an open framework through which seeds fall beside the stem.

Wild plants face serious pressure from collecting and habitat damage. Goats graze and trample the steep slopes where this cactus grows. It was once more frequent at the original collection site. LLIFLE now describes it as rare there and critically endangered.