阿勃勒（學名：Cassia fistula），又名金急雨、金链花、黃金雨、波斯皂莢、婆羅門皂莢、長果子樹、腊肠树、牛角树等、香港多稱豬腸豆，是一種蘇木亞科的植物。原產於南亞南部，從巴基斯坦南部往東直到印度及緬甸，往南直到斯里蘭卡。分布在缅甸、斯里兰卡、印度以及中国大陆的南部、西南部等地，生长于海拔1,000米的地区。
種植及用途
阿勃勒是一種中型樹，樹身可長至10至20米高，而且生長迅速。阿勃勒是一種落葉樹或半常綠樹，葉長15到60厘米，偶數羽狀複葉，每片樹葉有4到8對小葉片，每片長約7到21厘米、闊約4到9厘米，小葉對生，葉面平滑，全緣。花長在約20到40厘米長的下垂狀腋生總狀花序。花的直徑約4到7厘米，花瓣5枚離生，大小略等，雄蕊10枚，花絲黃色彎成勾狀，其中有3枚特長、4枚中等而另3枚較短為不孕性。花落後結出長棍棒狀不開裂莢果，長約30到60厘米，1.5到2.5厘米闊，需時一年才成熟，顏色由綠轉黑褐，每室有一種子，呈扁圓形有褐色光澤，果肉是瀝青狀黑色黏質，有一股刺鼻的氣味。種子有說味甜可食用，亦有說有毒，有輕瀉作用，古埃及人用此來作瀉藥用。樹皮含單寧，可作紅色染料。
阿勃勒一般可作景觀樹或行道樹之用，廣泛在熱帶及亞熱帶地區種植。花期在5月，初夏滿樹金黃色花，花序隨風搖曳、花瓣隨風而如雨落，所以又名「黃金雨」。為喜溫樹種，以砂質壤土最佳，排水、日照需良好，有霜凍害地區不能生長。繁殖可用扦插或播種法。
阿勃勒是泰國的國花，當地稱為「Dok Khuen」，其黃色的花瓣象徵泰國皇室。而2006年在「清邁農業研究中心」（Royal Agricultural Research Center）舉辦的「世界園藝博覽會」即以阿勃勒命名稱為「佛曆2549年世界崇頌叻差弗花苑博覽會」（Royal Flora Ratchaphruek 2549），「叻差弗」（Ratchaphruek）是「Dok Khuen」的別名，而「佛曆2549年」即西元2006年，「崇頌」即泰王普密蓬，是泰王登基60週年慶典之.
阿勃勒亦是印度南部喀拉拉邦的「省花」，當地稱為「kanikkonna」，是當地新年（Vishu）典禮用的花卉。
The Golden Shower Tree is a medium-sized tree growing to 10–20 m (33–66 ft) tall with fast growth.
The leaves are deciduous, 15–60 cm (6–24 in) long, pinnate with 3–8 pairs of leaflets, each leaflet 7–21 cm (3–8 inches) long and 4–9 cm (1.5–3.5 in) broad. The flowers are produced in pendulous racemes 20–40 cm (8–15 in) long, each flower 4–7 cm diameter with five yellow petals of equal size and shape. The fruit is a legume, 30–60 cm (12–23 in) long and 1.5–2.5 cm (0.5–1 in) broad, with a pungent odor and containing several seeds. The seeds are poisonous.
Cultivation and uses
Cassia fistula is widely grown as an ornamental plant in tropical and subtropical areas. It blooms in late spring. Flowering is profuse, with trees being covered with yellow flowers, many times with almost no leaf being seen. It will grow well in dry climates. Growth for this tree is best in full sun on well-drained soil; it is relatively drought tolerant and slightly salt-tolerant. It will tolerate light brief frost but can get damaged if frost persists. It can be subject to mildew, leaf spot especially during the second half of the growing season. The tree will bloom better where there is pronounced difference between summer and winter temperatures.
Golden Shower Tree is known as aragvadha ("disease killer"). Its fruitpulp is used as a mild laxative, against fevers, arthritis, vatavyadhi (nervous system diseases), all kinds of rakta-pitta (bleeding, such as hematemesis or hemorrhages), as well as cardiac conditions and stomach problems such as acid reflux. The root is considered a very strong purgative, and self-medication or any use without medical supervision is strongly advised against in Ayurvedic texts.
Though its use in herbalism has been attested to for millennia, there has been rather little research in modern times. While the purgative action is probably due to abundant 1,8-dihydroxyanthraquinone and derivatives thereof, whether the reputed nervous system (anti-vatavyadhi) effects are real and what causes them is not known. While many Fabaceae are a source of potent entheogens and other psychoactive compounds, e.g. tryptamines, such plants are rarely found among the Caesalpinioideae. There is also a rare case of it being used for anal autoeroticism.
The golden shower tree is the national flower of Thailand; its yellow flowers symbolize Thai royalty. A 2006-2007 flower festival, the Royal Flora Ratchaphruek, was named after the tree, which is most often called dok khuen or ratchaphruek in Thailand.
The golden shower tree is the state flower of Kerala in India. The flowers are of ritual importance in the Vishu festival of Kerala state of India, and the tree was depicted on a 20 Indian rupees stamp. C. fistula is also featured on a 2003 joint Canadian-Thai design for a 48 cent stamp, part of a series featuring national emblems.
The tree has strong and very durable wood and has been used to construct "Ahala Kanuwa" in "Adems peek", "Sri Lanka", which is made of Cassia fistula (Ahala) heart wood.
