The silk tree lives no more than 50 years, so why does it keep thriving endlessly?
The year before last, a smallsilk treeseedling suddenly sprouted in my yard, which puzzled me greatly. The nearest silk tree to my home is over two hundred meters away, and they basically do not rely on birds to spread their seeds, so how did it get to my yard? Let's just assume this seed wasblown in by the wind.
No concept of what a silk tree looks like? Take a look at this picture, you definitely recognize it. Image: 4028mdk09 / wiki commons
This silk tree, injust a few short months, grew to the same height as me. Only then did I remember to remove it, but its roots went too deep to dig out, so I could only cut it off at ground level. Unexpectedly, last year it sprouted branches again from its base, and withina single growing seasonsurpassed its height from the year before. It just so happened that the yard was being renovated that year, and one or two summer-blooming trees were needed, and its position was also suitable, so it was kept. This year its height and crown spread have both reached 2.5 m. Although it has not yet reached flowering age, it already faintly has the air of summer shade.
This is that little silk tree of unknown origin. Image: Frost Moth
The silk tree of harmony and joy
Although it isa summer flowering tree, thename "hehuan" always carries a touch of spring. The word "hehuan" has two meanings: one is everyone celebrating together, harmony and joy; the second is the matter between men and women. In ancient times, hehuan mostly referred to the first meaning.
Xi Jin of the Western Jin dynasty wrote in "On Nourishing Life": "Daylily makes one forget worry, hehuan dispels [juān] anger." In ancient literature,hehuan is often compared with daylily. The ancients believed daylily could make people forget their sorrows, and hehuan's effect was similar,able to remove resentment and calm the mood。
Cui Bao's "Ancient and Modern Notes" says: "If you wish to dispel a person's anger, then gift them qingshang. Qingshang is hehuan. Plant it in the courtyard, and it makes people free of resentment." This means that if you have done something to wrong a friend,hurry and give them a bunch of silk tree flowers, and their anger will be dispelled, and you can happily play together again, everyone joyful. If you simply give them a tree and plant it in the yard, the effect is even better.
Seeing a tree like this, could anyone still be angry? Image: armaghangiah.com
The silk tree leaves that open at dawn and close at dusk
Another ancient name for the silk tree is hehun, also called yehe. The ancients discovered very early that the silk tree hasnyctinasty: when the sky grows dim in the evening, the silk tree's bipinnately compound leaves close, its pinnae fold toward the main leaf axis, and the leaflets also droop and close in pairs.
The bipinnately compound leaf of the silk tree. Original image: Gmihail / wiki commons; Chinese localization: hannah
The principle of nyctinasty is that the cells on the upper and lower sides of the bases of the silk tree's pinnae and leaflets differ in structure; when the plasma membrane and vacuole membrane sense changes in light, theybring about different turgor pressure changes in the cells on the two sides, causing the pinnae and leaflets to bend in a certain direction。
When night comes, the leaflets close in pairs, and the pinnae also fold together. Image: Trees That Please Nursery
Li Yu, the romantic wit of the Qing dynasty, leaned toward the second explanation of hehuan, namely the matter between men and women. In "Occasional Leisure Notes" he says: "This tree opens at dawn and closes at dusk; whenever it reaches dusk, its branches and leaves intertwine with each other, hence it is named hehuan”。
The silk tree's leaves "open at dawn and close at dusk." Image: pixabay
Li Yu believed that daylily's ability to make one forget worry was unreliable, while hehuan had solid benefits, so daylily could go unplanted, but hehuan must be planted, and must be planted near the couple's bedroom - this is what is meant by "the hehuan flower should be placed in a place of hehuan". Whether the couple separates or joins together should be synchronized with the opening or closing of the hehuan leaves, for this benefits both the people and the tree, "when people open, the tree also opens; when the tree closes, the people also close. Since people thereby increase their joy, the tree likewise grows more luxuriant - this is what is called people and place suited to each other." He also thought it best to water the silk tree with the overnight bathwater from the couple's shared bath, and swore that this method was personally tested and effective by him, and if you did not believe it, you should plant two trees yourself and compare them.
The silk tree bark that "harmonizes the mind"
There is a third explanation for the name hehuan, concerning the medicinal value of its bark. "Compendium of Materia Medica" records that hehuan bark "calms the five organs, harmonizes the mind, and makes people joyful and free of worry." Its theory probably comes from the silk tree leaves opening by day and closing by night,following the so-called "waxing and waning of yin and yang", and thereforeit is believed to calm and soothe the nerves, mainly treating depression and insomnia.
A silk tree in daytime. Image: Cs?rf?ly D / wiki commons
Long Fu of the Yuan dynasty records in "Women's Needlework Remnants" that a man named Du Gao - his wife, Madam Zhao, would gather some silk tree flowers every year at the Dragon Boat Festival and place them in his pillow. When Du Gao was in a bad mood, Zhao would take a small amount of silk tree flowers, put them in wine, and have a maid deliver it to him to drink; after drinking, his mood would improve.I rather think it was not the hehuan that improved his mood, but the wine and the maid.
Looking at flowers like these, it probably really does improve one's mood. Image: Pixabay
The short-lived yet undying silk tree
The silk tree isa relatively popular street tree, because it can provide lovely flowers and dense shade in early summer. Moreover, it grows quite fast, just like the one in my yard, which can grow to nearly 2 m within a single growing season. It is expected to reach 6 m within 6 years, with a diameter at breast height of 15 cm, making it a qualified garden tree. After 10 to 20 years, it can reach as high as 15 m, with a shade area of 200 sq m, but by that age, its life is also nearing its end.
As a street tree, the silk tree's tall form, dense shade and lovely flowers make it quite popular. Image: Fanghong / flickr
Unlike those ornamental trees that routinely live for hundreds of years,the silk tree has a very short lifespan, with an average lifespan of about 25 years and a maximum of no more than 50 years, which is completely out of proportion to its large size. The reason is thatthe silk tree is relatively susceptible to infection by a fungus, leading to blight. The silk tree street trees in my hometown, about ten or so years old, have roughly half of the branches in their crowns dead. Moreover, the silk tree's branches and trunk are relatively fragile, making it easily damaged by wind and rain.
Although the aboveground part is short-lived, the silk tree's sprouting ability and growth speed make up for this; its roots are fully capable of sprouting a large patch of seedlings before the main trunk dies, and growing to the size of the main trunk within a few years.In this sense, the silk tree never dies, but is constantly cloning itself.
An old tree infected by fungus, with sprout seedlings growing from the roots, and in the foreground a seed-grown seedling. Original image: invasive.org; annotations: hannah
The silk tree's seeds are also very tenacious; the seed pods can be spread by wind to over a hundred meters away (the one in my yard may have come about this way), and the seeds can still germinate after decades of dormancy. The silk tree's life is short but full of explosive energy,and it has been listed as an invasive plant in multiple countries。
The seed pod of the silk tree. Image: treegrow / flickr
The dried seed pod and seeds of the silk tree. Image: Finca la Casilla / flickr
The silk tree flower like a pink fuzzy ball
The entire genus Albizia has about 150 species, widely distributed in tropical and subtropical regions. And the silk tree (Albizia julibrissin) is among themthe onlyspecies distributed in the Northern Hemisphere, its native range spanning the whole of Asia, west to Turkey and east to the Korean Peninsula.
In "Ten Fine Hounds" painted by Giuseppe Castiglione of the Qing dynasty, the background of Xuezhualu is a silk tree. Image: wiki commons
The silk tree entered the Western world relatively late. In 1745, the Florentine naturalist Filippo degli Albizzi introduced it from Constantinople to Europe, and in the same year it was introduced to North America. Filippo was from a declining noble family of Florence, whose ancestors had also once been prosperous - in the 14th century the Albizzi family was once the center of Florence's oligarchic rule, until the rise of the Medici family in 1434. Little did they expect that over 400 years later,this family surname would become the genus name of Albizia, thus achieving immortality in the plant kingdom。
The residence of the Albizzi family, who were once rivals of the Medici family. Image: sailko / wiki commons
Because the silk tree entered Europe from West Asia, and because its flowers are shaped like hanging silk threads, Westerners call it Persian silk tree; this "silk" is the main ornamental part. The silk tree'ssingle flower is very small, with the corolla and calyx together less than 1 cm, forming along tube shape; but the pinkstamenscan reach up to 3 cm. Many small flowers gather together to form a capitulum, and their stamens thus form a pink fuzzy ball.
The flowers of the genus Albizia are indistinctly dimorphic; within a single capitulum,the central flowersusually have longer, more vividly colored filaments; these flowers are sterile and serve only to attract long-proboscis pollinating insects and hummingbirds. While theperipheral flowersare shorter and smaller, with paler filaments, and this part is what sets seed.
Image: Philmarin /wikipedia; Chinese localization: Frost Moth
The silk tree's relatives and the silk tree's cultivars
Plants in the Mimosoideae subfamily all have fuzzy-ball-like inflorescences, which makes distinguishing them difficult. For example, in North America, the silk tree is often called mimosa, while in English "mimosa" refers both tothe genus MimosaMimosa, and sometimes tothe genus AcaciaAcacia。
To separate them from Albizia, what is the key thing to look at? The genus Mimosais mostly herbaceous or shrubby, very rarely trees, and the single flower of Mimosa generally has no more than 10 stamens. While the genus Acacia'sflowers are definitely yellow。
The compound leaf of Mimosa pudica usually has only 2 pairs of pinnae (that is, 4 leaflets). Image: tohumlar.net
The silk tree (A. julibrissin) has quite a few horticultural cultivars, such as the purple-leaved cultivar "Summer Chocolate". There is also the relatively famous "Ernest Wilson", introduced to the Americas from Korea by the famous plant hunter Ernest Wilson. This cultivar is characterized by being short and small, and in Japan it is often grown as a potted plant, calledねむの (sleeping tree)。
Purple-leaved cultivar 'Summer Chocolate'. Image: arbresetplantes.fr
In haiku, the silk tree is one of the seasonal words representing summer. Whether it is the stamens swaying like red threads under the moonlight, or the leaves quietly closing in the stillness, both carry one into a beautiful midsummer night's dream.
This article is the 164th article of the 4th year of Species Calendar, from Species Calendar author @Frost Moth.
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