Selenicereus is often called moonlight cacti or night-blooming cereus. It is a genus of mostly forest-dwelling, climbing cacti known for large, fragrant flowers that open at night and for producing pitaya, or dragon fruit. The name, coined by Britton and Rose in 1909, combines the Greek selēnē ("moon"), a nod to the nocturnal blooms, with Cereus, the name of a related cactus genus derived from the Latin word for "candle" or "wax taper." Together it means roughly "moon cereus." The former genus Hylocereus, which includes the dragon fruit, was merged into Selenicereus following a 2017 phylogenetic study, though older sources still use the earlier name.
Most species are epiphytes, growing on trees, or lithophytes, growing on rocks, and many scramble up trunks in tropical forests. They are native to Mexico, Central America, the Caribbean, and northern South America. Their sprawling, vine-like stems are ribbed, angled, or flattened, and aerial roots help them cling to trees, rocks, and walls.
The flowers are typically white, can be very large, and open at sunset, usually lasting only one night. They are pollinated mainly by bats and moths. The fruits are scaly berries, and several species are farmed commercially as dragon fruit. The name pitaya is the common regional and historical term for these fruits, believed to come from a Taíno or Caribbean word, with a popular (though debated) meaning of "scaly fruit." It is widely used in Latin America, while "dragon fruit" is more common in Asia and English-speaking markets. The fruit is prized for its striking appearance, mild sweetness, and fiber and vitamin C content.
Notable Species:
- Fishbone cactus (Selenicereus anthonyanus): A popular ornamental houseplant with distinctive zigzag stems and showy, fragrant night-blooming flowers.
- Queen of the Night (Selenicereus grandiflorus): A famous night-bloomer with large white flowers and a strong, sweet, vanilla-like fragrance.
- Yellow pitaya (Selenicereus megalanthus): Yellow skin and white flesh, often considered among the sweetest pitayas. The fruit has spines when young that fall off as it ripens.
- Dragon fruit (Selenicereus undatus): Pink-red skin with green-tipped scales and white flesh, the most widely marketed dragon fruit.
- Red pitaya (Selenicereus costaricensis, formerly Hylocereus costaricensis): Red skin and deep magenta flesh, often sweeter and more richly colored than white-fleshed types.
It is fascinating to follow the bloom cycle of the pitaya and how a flower becomes a fruit. Over roughly two to four weeks, the flower bud elongates into a large, tapering bud. When it matures, it begins to open at dusk and is fully open by late evening. Its mild, sweet fragrance attracts night-time pollinators, mainly bats and moths.
The bloom is short-lived. A single flower lasts only one night, and by the following morning its petals wilt and close.
What happens next depends on pollination. If the flower is pollinated, the ovary at its base stays green and swells, and over the next 30 to 50 days it develops into a ripe dragon fruit. If pollination fails, the flower and ovary turn yellow and drop from the plant within a few days. Pitaya usually flowers in several waves during the warm season, which is why a single plant can produce more than one harvest a year.
蛇鞭柱屬常被稱為「明月仙人掌」或「曇花」。該屬植物多為生長於森林環境的攀緣性仙人掌，以其夜間開放的大型芳香花朵以及結出火龍果而聞名。這個屬名由布里頓（Britton）和羅斯（Rose）於 1909 年命名，結合了希臘語 selēnē（意為「月亮」，以此呼應其夜間開花的特性）與 Cereus 仙人柱屬（源自拉丁語中「蠟燭」或「蠟燭芯」一詞，也是一個親緣關係相近的大屬名），合起來稱月下美人(曇花或月神花)。原先包含火龍果在內的量天尺屬（Hylocereus）在 2017 年的一項系統發育研究後被歸併入蛇鞭柱屬，一些較早的資料仍沿用舊名。
大多數物種屬於附生植物（生長於樹木上）或岩生植物（生長於岩石上），其中許多物種在熱帶森林中沿著樹幹攀緣生長。它們原產于墨西哥、中美洲、加勒比地區及南美洲北部。其蔓生、藤狀的莖幹呈棱紋、有角或扁平狀，並長有氣根，有助于植株附着在樹木、岩石和牆壁上。
花通常是白色，體型碩大，於日落時分開放，花期往往只有一晚，主要依靠蝙蝠和蛾類授粉。果實是有鱗片的漿果，其中數個品種被商業化種植，即我們熟知的「火龍果」。「Pitaya」是這些果實常見的地區性及歷史性稱呼，據信源自泰諾語（Taíno）或加勒比語，其含義通常被解釋為「有鱗片的果實」（儘管這一說法尚存爭議）。這個名稱在拉丁美洲廣泛使用，而「火龍果」（dragon fruit）這個名稱則在亞洲及英語國家市場更為普遍。這種果實因其獨特醒目的外觀、清甜的口感以及豐富的纖維和維生素 C 含量而備受青睞。
顯要的物種：
- 紫魚骨令箭（Selenicereus anthonyanus）：也常被稱為魚骨令箭、之字形仙人掌、魚骨仙人掌或鋸齒曇花。是一種廣受歡迎的觀賞性室內植物，具有獨特的鋸齒魚骨狀莖，以及在夜間開出醒目、香氣怡人的花朵。
- 大花蛇鞭柱（Selenicereus grandiflorus）：也常被浪漫地稱為夜之女王或月光花。一種著名的夜間開花植物，花朵碩大潔白，散發著濃鬱甜美、類似香草的芬芳。
- 黃麒麟量天尺（Selenicereus megalanthus）：其果實通稱黃龍果、麒麟果 或燕窩果。果皮黃色，果肉白色，常被認為是最甜的火龍果品種之一。果實幼嫩時帶有尖刺，成熟後尖刺會脫落。
- 量天尺（Selenicereus undatus）：其果實即為常見的白心火龍果，花朵則被稱為霸王花（或稱劍花）。果皮呈粉紅色，帶有綠尖鱗片，果肉為白色；這是市面上最常見的火龍果品種。
- 哥斯達黎加量天尺（學名：Selenicereus costaricensis，曾用名：Hylocereus costaricensis）：俗稱或別名為紅心火龍果、哥斯達黎加火龍果或哥斯達黎加夜花仙人掌。果皮呈紅色，果肉呈深紫紅色；與白肉品種相比，其口感通常更甜，色澤也更為濃鬱。
觀察火龍果的開花週期以及花朵如何轉變為果實，是一件極有趣的事情。在約兩到四周的時間裡，花蕾會逐漸伸長，變成一個碩大且末端漸尖的花苞。花苞成熟後，會在黃昏時分開始綻放，並於深夜完全盛開。其散發出的淡淡甜香會吸引夜間活動的授粉者，主要是蝙蝠和蛾類。
花期短暫。單朵花僅能維持一夜，到了隔天清晨，花瓣便會凋萎閉合。
接下來發生的事情取決於授粉。如果花被授粉，其基部的子房會保持綠色並膨脹，在接下來的 30 到 50 天裡，它會發育成成熟的火龍果。如果授粉失敗，花朵和子房會變黃並在幾天內從植物上掉落。火龍果在溫暖的季節通常會分成幾次開花，這就是為什麼一株植物一年可以收穫多次的原因。
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