Scenery • Paulownia in Wuhan

Produced by: Science Popularization China

Author: Liu Congkang

Producer: China Science Expo

Review: Wuhan Botanical Garden, Chinese Academy of Sciences

Hometown, foreign land

Every place usually has its own kind of plants.

Northeasterners who "fly south" never forget the large-leaf celery and pig's tooth flowers in the mountains and forests of their hometown; when they arrive in the streets of Guangzhou and Shenzhen, the banyan trees with thick shade and the huge red kapok flowers are tropical scenery that "northerners" are not familiar with. In the grassland desert of Xilin Gol, clusters of large spiny thistles and blue echinops are in full bloom, as if in a dream; on the shore of the Bohai Sea, pink flowers of rhubarb bloom on the steep hillsides, and roses quietly bloom and produce fiery red fruits in the black pine forest on the coastal sand. Many years ago, during a heavy rain, a dirt road on the barren and arid Loess Plateau wound its way to the top of the plateau, which the villagers called "Tianling". The mud underfoot was as slippery as ointment, and the dense jujube bushes on the roadside were covered with sharp thorns, with nowhere to grab; many years later, the two rivers and three towns are lush all year round, and the vitex flowers bloom in early summer, with bees and butterflies flying among the dense inflorescences, but it is difficult to find any trace of the jujube trees.

Walking in the shadows of tall buildings, stuck in traffic on elevated roads, and passing through darkness in the gentle clang of subway cars, arriving at and leaving the brightly lit platforms one by one, the plants and trees around us often remind us of our hometown, and at the same time soothe our hearts in a foreign land - such as Paulownia.

Paulownia tomentosa, Paulownia odorifera

Paulownia is widely distributed in most parts of China. It can be found in hilly and plain areas except grasslands, deserts and high-altitude mountains. At the same time, Paulownia has been a "companion plant" closely related to human life since ancient times. Even if you are away from home, you can often see the familiar Paulownia.

"Book of Songs: Yongfeng: Dingzhi Fangzhong" is a poem praising Duke Wen of Wei for leading his people to rebuild the capital of Wei during the Spring and Autumn Period (around 661-662 BC). The poem says: "It was built in the Chu Palace. Plant hazelnuts, tung trees, lacquer trees, catalpa trees, and paulownia trees." The Wei people who moved to other places planted catalpa trees, lacquer trees, catalpa trees, and paulownia trees, and the foreign land became their hometown. The Northern Dynasty agricultural book "Qimin Yaoshu" (written around the early years of the Eastern Wei Dynasty, around 540 AD) records: "White tung trees...dig pits around big trees, take them out and plant them", which is the earliest record of artificial root division and propagation of paulownia trees; Chen Zhu of the Northern Song Dynasty wrote "Tongpu" (written around 1049 AD), which clearly divided paulownia trees into two types: "white tung trees" (now white tung trees) and "purple tung trees" (now hairy paulownia trees).

Paulownia tomentosa

(Photo credit: Photo taken by the author)

Since Paulownia is a native plant of China, the process of its recognition by modern Western botany is rather tortuous. The first Western scholar to study Paulownia was Swedish botanist Thunberg. In 1783, he mistakenly identified the specimen he collected in Japan as Bignonia tomentosa. "Tomentosa" means "hairy" and "Bignonia" refers to Bignonia, which means that he thought it was a Bignonia plant. In 1825, botanist Springer changed it to Artemisia after studying the specimen.

In 1823, botanist Siebold collected 12,000 plant specimens in Japan. In 1835, he and his assistant Zuccarini established the genus Paulownia after studying one of the specimens and named it Paulownia imperialis. In 1841, Steedel studied the original specimen of Thunberg and believed that it was Paulownia imperialis, and the Latin name should be changed to Paulownia tomentosa, which is the type species of the genus Paulownia.

The flowers of Paulownia tomentosa are purple, and the inflorescence branches can be up to about 60 cm long. There are often three or four side branches at the bottom of the inflorescence branches, and the length of the side branches is usually no more than half of the main branches, so the whole inflorescence is pyramid-shaped; the fruit is short and oval. The Paulownia tomentosa in Wuhan usually starts to bloom in early March and enters the peak flowering period around the spring equinox. The flowers of Paulownia tomentosa are first bloomed and then leaves, and the flowers are large. When blooming, the tree is full of pink and purple, which is very beautiful. In the bustling city center of Wuhan, Fuli Road on the south side of Hankou Railway Station and Bagodun Lane 1 on the east side of Tangjiadun Road are two quiet streets, and Paulownia tomentosa is planted on both sides of the street as street trees. In spring, the flowers bloom, and the branches of the Paulownia trees on both sides are connected, like a tunnel of flowers.

Paulownia tomentosa

(Photo credit: Photo taken by the author)

Like many Chinese plants, Paulownia tomentosa entered the field of vision of Western botanists through Japan. However, the specimens of the second species of Paulownia tomentosa known by modern botany, Paulownia alba, came directly from mainland China.

In 1842, the Qing government signed the Treaty of Nanjing with Britain, which gave the British the right to freely enter and reside in Guangzhou, Fuzhou, Shanghai and other trading ports, allowing Westerners to explore China. In 1843, plant hunter and Scotsman Robert Fortune was hired to collect plant specimens in China. Fortune disguised himself as a Chinese more than once, walked out of the trading ports agreed in the treaty, and went deep into the hinterland of southern China to collect plant specimens. Through Fortune's hands, hundreds of beautiful Chinese plants were "stolen" to Europe; but his most famous "theft" was in 1848 when he was hired by the British East India Company to smuggle Chinese tea trees and some skilled tea-making workers to India. In 1867, German botanist Berthold Carl Seemann named a specimen collected by Fortune "Campsis fortunei", mistakenly thinking it was a plant of the genus Campsis.

In 1882, Augustine Henry, a 25-year-old Irishman, came to Yichang, Hubei as an employee of the Imperial Customs Commissioner of the Qing Dynasty. Henry was attracted by Chinese plants and began to teach himself to become a botanist. He collected plant specimens and sent them to Kew Gardens in London. Before Henry, Western botanists' footprints in China were limited to the southeastern coastal areas, and they knew very little about plants in central China. The plant specimens collected by Henry became the main source of information for the first volume of the three-volume "List of Chinese Plants" (1886-1905) published by the Linnean Society of London. The author of the book, William Botting Hemsley, a member of the Linnean Society of London, re-studied Campsis fortunei published by Seemann in 1867 and found that this plant, which was considered to be a trumpet creeper, was actually a "new species" of the Paulownia genus. Hemsley changed the scientific name of the plant to Paulownia fortunei, which is today's white Paulownia.

The flowers of white Paulownia are white to light purple, and the inflorescence branches are short, generally not exceeding 30 cm, with few side branches, so the whole inflorescence is mostly wide cylindrical; the fruits of white Paulownia are large, up to seven or eight centimeters long, and oblong. White Paulownia is mainly distributed in the Yangtze River Basin and the areas to the south. In Wuhan, it is mostly scattered, and white Paulownia can often be seen in parks, green spaces, and community roadsides. Among the trees on the southern foot of Sheshan Mountain in Wuchang, Wuhan, there is a "Baobing Hall" built to commemorate Zhang Zhidong, a famous minister of Westernization. In front of Baobing Hall, there is a white Paulownia with a breast diameter of more than 60 cm. It is tall and upright, which is very spectacular.

Paulownia chuanxiensis, Paulownia huadongensis

Paulownia tomentosa and Paulownia alba are the two most common species of the genus Paulownia, but there are more to the genus. In 1867, Paul Guillaume Farges, a 23-year-old French missionary and botanist, came to China and preached there until his death in 1912. During this period, he collected many plant specimens and sent them to the Paris Museum of Natural History, making important contributions to the world's understanding of the unique plant communities in western Hubei and eastern Sichuan. The Latin genus name of the genus Fargesia is named in his memory. In 1896, Adrien Rêne Franchet, a botanist working at the Paris Museum of Natural History, identified another Paulownia plant based on Farges' specimens and named it Paulownia fargesii, which is what we call Sichuan Paulownia today.

The length of the side branches of the Paulownia inflorescence can exceed half of the main branches, so the inflorescence is a wide cone, with a length and width of more than 1 meter. It is a very beautiful Paulownia. You can see Paulownia in Wuhan Botanical Garden and Qintai Park.

Although the Paulownia kawakamii is beautiful, it is not the most beautiful of the Paulownia genus. There is a small Paulownia tree on the roadside near the Pacific Bus Station on Jiefang Avenue in Wuhan. Its flowering period is slightly later than that of the white-flowered Paulownia and the tomentosa. Although the flowers are small, the side branches of the inflorescence branches are almost as long as the main branches. The length of the entire inflorescence branch is nearly 2 meters, wide and large, with dense and colorful flowers, which is extremely gorgeous. This is a "Paulownia kawakamii" tree that is relatively rare in Wuhan.

Paulownia trees of Kawakami family on Jiefang Avenue in Wuhan

(Photo credit: Photo taken by the author)

Kawakami Paulownia was named in 1912 by botanist Atsutaro Ito, grandson of Keisuke Ito, one of the founders of modern Japanese botany. The specific epithet kawakamii is to commemorate the Japanese botanist Kawakami Takiya. Kawakami Takiya was born in 1871. In 1903, he served as a technician in the "Taiwan Governor's Office" (Taiwan was occupied by Japan after the Sino-Japanese War of 1895). In 1905, he began to preside over the plant survey work in Taiwan, and his footprints covered the entire island of Taiwan and outlying islands such as Penghu and Lanyu.

Although the Chinese name of Paulownia kawakamii in the Flora of China (Chinese version) is "Taiwan Paulownia", paulownia experts such as Chen Zhiyuan from Huazhong Agricultural University call it "East China Paulownia". This is not only because the main distribution area of ​​Paulownia kawakamii is actually in the central and eastern regions of my country, but also because the name "Taiwan Paulownia" is redundant and ambiguous.

From 1973 to 1976, my country conducted its first national forest resource inventory, and the results showed that my country's forest coverage rate was only 12.7%, especially in the "Three Norths" regions such as Northwest China and North China, where it was only about 5%. In order to rapidly increase forest coverage and improve the ecological environment, Paulownia, as an important fast-growing tree species in the "Three Norths", became the focus of the Chinese government and botanists. The 1970s and 1980s also became a climax of Paulownia research and application in my country. The 67th volume of the Flora of China, where the Paulownia genus is located, was published in 1979. There are a total of 7 species of Paulownia included in the book: in addition to Paulownia tomentosa, Paulownia alba, Paulownia chuanxiensis, and Paulownia kawakami, there are also added Lankao Paulownia (Paulownia elongata), Catalpifolia (Paulownia catalpifolia) and Paulownia australis (the specific epithet means "southern"). Among them, Lankao Paulownia was named by Chinese botanist Hu Xiuying in 1959 based on the Chinese plant specimens collected by Harvard University; Paulownia catalpa and Paulownia australis were announced by the National Paulownia Research Collaboration Group in 1976 under the name of "Gong Tong".

Paulownia suspensa, also known as Taiwan Paulownia

(Image source: China Plant Image Library)

When Gong Tong published the name of Paulownia australis, he was unaware that in 1975, Taiwanese scholars Hu Dawei and Chen Huizhu published a new species of Paulownia based on native plants in Taiwan, China: Paulownia taiwaniana, with the specific epithet meaning "Taiwanese". When the 67th volume of Flora of China was published in 1979, the relationship between Paulownia australis and Paulownia taiwaniana was still uncertain. The book said: "Because there is no information at hand, no specimens, original records and illustrations, whether this species is a close relative of Paulownia australis or a synonym of the same thing will be studied and resolved in the future." In fact, shortly after the 67th volume of Flora of China was published, botanists discovered that Paulownia australis and Paulownia taiwaniana were indeed synonyms of the same thing. According to the naming rules of plant Latin names, "Paulownia australis" should be abolished, but the Chinese name is not included in this rule. Therefore, in some Chinese literature, Paulownia kawakamii, which should be translated as "Kawakami Paulownia", was called "Taiwan Paulownia", while Paulownia taiwaniana, which should be translated as "Taiwan Paulownia", was still called "Southern Paulownia" - this "contradiction" caused some researchers to make ridiculous mistakes:

A paper using ISSR markers to study the evolution of Paulownia plants stated: "Previously, many reports believed that Taiwan Paulownia and Taiwan Paulownia were synonyms. This study will correct this view." The authors of this paper mistakenly believed that the "synonyms" were Paulownia kawakamii and Paulownia taiwaniana, so they proposed to "correct this view" based on their own experimental data, which is "realistic." Another paper using FISH-AFLP markers to study the genetic diversity of Paulownia plants stated: "Chen Zhiyuan et al. (Chen Zhiyuan. Origin, evolution and geographical distribution of Paulownia. Wuhan Botanical Research, 2000, 18 (4): 325-328) believed that the southern Paulownia (Paulownia australis) and the Taiwanese Paulownia (Paulownia kawakamii) should be combined into one species and that the southern Paulownia should be used as a synonym. This study provides a certain theoretical basis at the DNA level." The original text in Chen Zhiyuan's article "The Origin, Evolution and Geographical Distribution of Paulownia" published in "Wuhan Botanical Research" Volume 18, 2000 is: "Southern Paulownia (Paulownia australis) and Taiwan Paulownia (Paulownia taiwaniana) should be combined into one species, and southern Paulownia should be used as a synonym." The author of this paper misunderstood the "Taiwan Paulownia (Paulownia taiwaniana)" in Chen Zhiyuan's article as "Taiwan Paulownia (Paulownia kawakamii)", and his experimental data actually "provided a certain theoretical basis" for this misunderstanding, which is quite amazing.

Lankao Paulownia, Catalpa ovata

Among the seven species of Paulownia included in Flora of China, Paulownia tomentosa, Paulownia alba, Paulownia chuanxiensis, and Paulownia kawakamii were named earlier; Paulownia lankaii was named by Mr. Hu Xiuying in 1959, and Paulownia catalpa and Paulownia australis were named by Gong Tong in 1976. In addition, in the 1980s, Zhu Zhaohua, Chen Zhiyuan and others published new species such as Paulownia chuanxiensis, Paulownia shanmingensis, Paulownia yichangensis, and Paulownia jianshiensis.

Paulownia lankaoensis

(Image source: China Plant Image Library)

Paulownia catalpa

(Image source: China Plant Image Library)

Zhu Zhaohua, Chen Zhiyuan and others believe that the Paulownia genus originated in the early Paleogene and differentiated into East China Paulownia (Paulownia kawakamii) and Paulownia tomentosa in the Miocene of the Neogene; subsequently, it differentiated into white-flowered Paulownia and Sichuan Paulownia. With these four Paulownia species as the basic species, the natural hybridization of Paulownia tomentosa and white-flowered Paulownia formed the Lankao Paulownia; the hybridization of white-flowered Paulownia and East China Paulownia formed the southern Paulownia; while the Echuan Paulownia is a hybrid of the southern Paulownia and the Lankao Paulownia; the Shanming Paulownia is a hybrid of the hairy Paulownia and the Lankao Paulownia; the Yichang Paulownia and the Jianshi Paulownia are both hybrids of the Sichuan Paulownia and the white-flowered Paulownia. Among the Paulownia species of hybrid origin, the distribution areas of the Echuan Paulownia, the Shanming Paulownia, the Yichang Paulownia and the Jianshi Paulownia are very narrow, and the plants seen are all artificially cultivated.

Lankao Paulownia is a "celebrity" in the Paulownia genus. It is named after Lankao County, Henan Province, where Jiao Yulu once worked, but its distribution area is actually as wide as Shanxi, Hebei, Shandong, Henan, Shaanxi, Gansu, Hunan, Hubei and other vast areas. In Wuhan, the number of Lankao Paulownia may be second only to the tomentosa and white-flowered Paulownia. Lankao Paulownia can be seen in schools such as Huazhong Agricultural University and Hubei University of Traditional Chinese Medicine, Wuchang Railway Station Square, and Changdi Street in Hankou. The appearance of Lankao Paulownia is between the tomentosa and white-flowered Paulownia: the leaves are hairy on the back and usually smooth on the front; the inflorescence branches have side branches but are usually shorter; the fruits are usually close to the oval shape of the tomentosa, but there are also longer ones. There is still controversy as to whether the catalpa-leaf Paulownia is a natural evolution or hybrid origin. Its morphology is similar to that of the Lankao Paulownia, but the leaves are hairless and shiny on the front, and the length of the leaves is nearly twice the width, resembling the leaves of the catalpa. There was once such a Paulownia in Xiaoli Village, Lumo Road, Wuchang, but it is no longer seen.

How many species of Paulownia are there in the streets and alleys of Wuhan? When do they bloom and when do they fall? No "professional" "flora" will care about this question, but in the eyes of some people, this is precisely the hidden charm of a city.

(Note: Latin text should be italicized.)