The tropical rain tree (Samanea saman) grows up to 200 feet in height with a crown that spreads to a width of 240 feet. Widely grown as a shade tree, it offers abundant evergreen bipinate leaves. The leaves measure up to 15 inches in length. The tree thrives in U.S. Department of Agriculture zones 9 to 11.
The rain tree grows native in the northern regions of South America, but it is now naturalized throughout a wide majority of tropical locations around the world. It grows well in savannas, forestlands and riparian areas. The tree grows in the southern United States, West Indies and Mexico as a coveted shade specimen. In areas such as Fiji and Vanuatu, the tree has become invasive and is considered to be a nuisance.
The tree thrives in a wide range of soil pH levels. It grows best at an elevation ranging from sea level up to 1,000 feet. The tree prefers between 24 to 120 inches of rainfall annually for maximum growth. An annual temperature of 68 to 100 degrees Fahrenheit is ideal for the rain tree. The tree cannot withstand temperatures below 46 degrees Fahrenheit.
The rain tree grows approximately 5 feet per year. It requires full sunlight and does not tolerate shade well. The foliage of the tree has the unique quality of folding up together during rainy weather and the night hours. When the trees foliage folds together, the rain runs straight down and onto the ground. Due to the extra moisture under the tree, grass always grows against the rain tree's trunk.
Flowers and Pods
Fluffy flower clusters with abundant stamens appear in shades of white and pink. Flowers grow near the end of the tree's twigs and look similar to tiny powder puffs. Long seed pods appear following flowering. Each pod contains up to 20 seeds. Pods measures 8 inches in length. The pods quickly turn black and lumpy in appearance as they dry out. Within each pod is a sticky substance that is edible. Seeds are dispersed when cattle or other large mammals consume the pods and then eliminate the seeds.
The rain tree provides numerous uses around the world. The tree attracts large amounts of bees, which utilize it for honey production. The seed pods of the tree make excellent animal fodder for livestock, so planting rain trees in pasturelands is becoming an ever-increasing occurrence. The wood of the tree is used widely in the timber industry and as a fuel wood.
A member of the legume family, the rain tree has the capability to fix nitrogen into the soil by its root system and a symbiotic relationship with the bacteria rhizobia. This capability helps grass to remain green and healthy under the tree's canopy. When rain tree seeds are planted, germination occurs quickly, within three to four days. At five months of age, the tree has normally attained a height of 12 inches.