Among the most brilliant of flowering trees are those in the Fabaceae, or legume, family of plants. Imagine, for example, a tree with long golden chains of five-petaled flowers, so profuse that they completely obscure the tree’s foliage. This species is appropriately named golden shower tree or laburnum of India (Cassia fistula) and will remind you of true laburnum, the tree that is classically associated with long chains of yellow flowers.
Throughout Southeast Asia, the golden shower tree is revered both for its beauty and for its medicinal properties in combating a large variety of ailments, from colds to stomach ailments to skin disorders. The national flower of Thailand is the one that hangs from it in lavish pendant clusters. As members of the legume family, the seeds of both golden shower and true laburnum are contained in elongated pods. However, true laburnum is native to the cold winter climate of the French Alps and will simply not flower in Southern California.
Golden shower tree, however, is well-suited to our climate so it is a mystery why you seldom see it here. And there is another stunning leguminous tree in gold, also strangely absent from our gardens. It is called copperpod (Peltophorum pterocarpum) due to the color of its pods, while its overall form, foliage, and flowering season correspond to those of the jacaranda. Both golden shower and copperpod are medium-sized trees, 30-40 feet tall, and hardy to 25 degrees Fahrenheit so they should make it through Southern California winters just fine.
You can locate seeds of both golden shower tree and copperpod on eBay which, I must say, appears to offer through its vendors the widest selection of exotic seeds anywhere on the Internet.
The procedure for germination of seeds from leguminous trees is the same for all species. These seeds generally have hard seed coats on account of their drought tolerance, giving them the ability to survive many years of drought without loss of vitality until rain finally comes. Leguminous tree seeds may also contain chemicals that prevent germination until, when seeds are finally submerged in water after a soaking rain, these chemicals are diluted or leached out. Therefore, you should first soften the coats and remove these chemicals by plunging the seeds in water that has just been boiled. Cover the container and keep the seeds in the cooling water for 24 hours. Although seeds of some leguminous tree species will germinate without pre-soaking. it has been demonstrated that pre-soaking increases the percentage of seeds that sprout. Especially hard seed coats of certain leguminous seeds will need to be scarified with a sharp object in order to open enough to absorb water and germinate through the opening.
Before leaving leguminous trees with golden flowers, two others are worthy of special mention. One of them is gold medallion tree (Cassia leptophylla). In my neighborhood, its annual opulent summer display got me thinking about its Latin name. Upon investigation, I learned that Cassia is derived from ke’tzia, which was one of the 11 spices used in the incense mixture that, in ancient times, was burned twice a day in the Holy Temple in Jerusalem. According to most opinions, ke’tzia had a cinnamon fragrance. It contributed to a perfumed mixture so purifying that it banished negative thoughts from all who inhaled its fragrance. Sure enough, the Latin name for cinnamon is Cinnamomum cassia. The bark of the gold medallion tree, although without fragrance, does bear some resemblance to the bark of the cinnamon tree which is used in the manufacture of the spice that bears its name. Because of its drought tolerance, gold medallion tree is used for reforestation of natural landscapes in arid zones that have been destroyed by fire or rendered barren due to overgrazing by animal herds.
Popcorn cassia (Cassia didymobotrya) has leaves that smell like buttered popcorn. Flowers are golden torches, born on a shrub-like tree that may grow up to eight feet tall. Flower buds are black and present a stunning contrast to the golden blooms that emerge from them during summer and fall. You can procure popcorn cassia by mail order from Annie’s Annuals (anniesannuals.com).
And now we come to mimosa (Albizia julibrissin), a legendary leguminous beauty. Mimosa (mi-MOH-sa) is a tree that looks like it sounds. It possesses fine, bipinnate foliage and delicate pink shuttlecock flowers. Mimosa, with its susurrating final syllable, suggests a whispering softness and, on account of its downy, feathery flowers, one of its common names is silk tree.
This tree has a unique growth habit. Generally speaking, trees with a mature height of 20 to 30 feet are not particularly fast-growing. The mimosa tree, however, despite being of such moderate stature, reaches its maximum height in just a few years. Alas, the mimosa, in the manner of other leguminous trees such as acacias, mesquites, cassias, and sennas is not known for longevity. During the two to three decades of its life, however, you will enjoy its annual flower display and stylish parasol form. Although mimosa has proven to be invasive in wetter climates, it does not pose a threat to wilderness habitats in Southern California and the Southwest. It should be noted that a cultivar with bronze foliage, known as ‘Summer Chocolate,’ is also available.
The origin of the word mimosa has nothing to do with the mimosa tree. Instead, it is derived from a creeping tropical legume – sometimes available as an indoor plant – known as Mimosa pudica or sensitive plant. The uniqueness of this sensitive plant is in its leaves, which fold up when touched. It was given the name Mimosa because its foliar folding was thought to mime or mimic the movement of animals in response to stimuli. The foliage of the mimosa tree, while it does not fold in response to touch, is similar in appearance to that of the sensitive plant.
California native of the week: The flowers of Apache plume (Fallugia paradoxa) look like small, single-layered white roses. This makes complete sense since the species is a member of the rose family. But then a remarkable transformation takes place as each rose turns into a collection of ethereal, feathery pink wisps that serve as seed dispersal agents. Once established, apache plume can make do with little, if any, summer water and can tolerate both light shade and imperfect soil drainage. Although usually planted as an accent shrub, it may reach six feet in height and, planted in a row, could serve as a low hedge or informal screen. Although deciduous, it makes up for its downtime by blooming for two months or more in spring and summer. Apache plume is available in one-gallon containers at Tree of Life Nursery (californianaativeplants.com) in San Juan Capistrano, while packets of its seeds — which germinate readily when fall-planted — are to be found at the Theodore Payne Nursery (theodorepayne.org) in Sun Valley.
Please send questions, comments and gardening comments to joshua@perfectplants.com.
