Say it: sten-oh-SEER-ee-us al-ah-moh-SEN-sis; pak-ee-SEER-ee-us mar-jin-AY-tus. Common names: octopus cactus or sina; Mexican fence post or organ pipe.
Where it grows
Both are Mexican. Stenocereus alamosensis is from Sonora and Sinaloa, in the thornscrub near Álamos. The Mexican fence post, now usually called Pachycereus marginatus, is from central Mexico, where whole villages are fenced with it.
Size and growth
Two very different habits. The octopus cactus sends out arching, sprawling stems that bend back to the ground and root, forming a tangle up to 10 feet across. The fence post grows as tight, straight columns 10–15 feet tall with a thin white line of areoles down each rib. Alamosensis is fast; marginatus is slow to moderate, which is why it makes such a tidy living fence.
Flowers and fruit
Alamosensis has bright red, day-opening tubular flowers for hummingbirds, followed by edible red fruit. Marginatus has small pink-red flowers along the ribs in spring and small spiny fruit.
Care
- Light: full sun.
- Water: regular in summer, dry in winter.
- Soil: fast-draining.
- Cold: both are frost-tender; keep above about 28°F.
From seed
Easy. Germination in 7–21 days. Fence post seedlings are slow for the first couple of years; octopus seedlings sprawl early.