Moon Cactus

A small, slow-growing, globular cactus. The top (scion) is a bright neon ball 2–5 cm (0.8–2 in) diameter, sometimes up to 7–8 cm, in red, orange, yellow, pink, purple, or bi-color—colors show because there’s no green pigment to mask them. Its body has 8–14 narrow ribs, small curved grey-yellow spines in clusters of 5–6 per areole, and a flattened round shape. The rootstock is a green, ribbed, columnar cactus (Hylocereus) that looks like a short stem (5–10 cm tall). Total height including pot is usually 8–15 cm (3–6 in). Flowers are rare indoors; if they appear they’re small funnel-shaped, pale green to pinkish-yellow, 5 cm across, at the crown. Lifespan is short (often 1–3 years) because the scion and rootstock grow at different rates and the graft eventually fails.

Quick care: bright indirect light (1–2 hrs gentle morning sun; strong direct sun scorches the colorful top, too little light makes the green base etiolate). Keep 18–27 °C (65–80 °F); minimum ∼10 °C (50 °F), no frost (USDA 9–11). Use a gritty cactus mix, excellent drainage, pot with drainage hole. Water sparingly—let soil dry completely, then water deeply (every 2–3 weeks in warm season, less in winter; light mist in winter). Low humidity is fine. Feed lightly with cactus fertilizer 2–3 times in spring–summer. Don’t repot often; if the base outgrows, you can re-graft onto fresh rootstock. Watch for mealybugs, spider mites; avoid overwatering (root rot). Non-toxic but spiny. Great as a desktop novelty, windowsill, or dish garden accent.