Paulownia

 

Paulownia is a genus of angiosperm trees, and one of the fastest-growing trees in the world.^[12] Paulownia tomentosa can grow over 30 metres (98 ft) tall and has large heart shaped leaves ranging from 10–20 centimetres (4–8 in) wide and 15–30 centimetres (6–12 in) long with a 10–20 centimetres (4–8 in)-long petiole.^[13] The leaves grow in opposite decussate pairs, and as the name tomentosa suggests, are covered in hairs. The leaf margin can be toothed or entire and sometimes may be slightly lobed. They can be distinguished from common look-alike genera, such as Catalpa and Cercis, by secondary and tertiary venation.^[14] The leaves are late to come in on the tree and late to fall from the typically deciduous Paulownia. However, in tropical areas, the tree can be evergreen.

The leaves are often preceded by pale violet to purple-shaded tubular flowers, similar to a foxglove. Like most members of the Lamiales, the flowers are zygomorphic. The inflorescences are terminal erect 15–30 centimetres (6–12 in)-long panicles of ~5 centimetres (2 in) long flowers.^[13] The thick, fused calyx is covered by a brown hairy indumentum, and the fused calyx tube is the same length as its calyx lobes, except in P. catalpifolia and P. elogata, in which the lobes are shorter than the calyx tubes.^[15] The corolla has five fused lobes with a shorter adaxial bilobed lip, and a somewhat longer abaxial trilobed lower lip. The lips of all the petals are curled and their surface tomentose.

 

On the inner side of the lower trilobed corolla tube run two light-yellow folded ridges from the calyx to the lip. They are interpreted as floral guides to the top of the corolla tube.^[13] Inside the corolla tube, and approximately halfway down, are four stamen filaments fused to the petals at the base, with two being longer than the others. At the bottom of the corolla tube is a short corolla-stamen tube. The base of the stamen filaments are bent so that they run along the upper portion of the flower with the arrow shaped anthers then depositing pollen on the dorsal side of a variety of pollen-feeding insects.

The superior bilocular ovary, surrounded by the brown calyx, with its stigma and style rising up, is approximately the same length as the longer stamen filaments that surround it. That is left on the stem as the corolla and stamen fall off. The stigma tip has a singular small hole that leads to a tubular dilated chamber at the top of the style, covered in receptive papillae. In the species P. kawakamii, the stigma tip is slightly bilobed, which is a unique morphological characteristic distinguishing Paulownia from all of the Lamiales.^[13] At the bottom of the ovary is a nectary, with nectary slits on the basal sides of the ovary, beneath a hairy region. The ovary then develops into a sticky green oval capsule tapered at the apex with the remaining dried up style sometimes still attached.

The capsule remains on the persistent brown calyx where it can last on the tree through the rest of the year before turning brown and woody, and loculicidal dehiscence reveals up to 2000 small winged seeds stacked tightly inside. The tiny seeds have lateral wings that gradually increase in length around the seed. The ventral and dorsal side of the seed are flat. The wing shape on the seeds is another characteristic distinguishing Paulownia from the rest of the Lamiales.^[13] The new buds, enclosed by the early brown fuzzy calyx, are visible in late summer to early fall and wait dormant, alongside the brown seed capsules, till spring.

Paulownia once occurred in North America, with fossilized leaves being found in Tertiary strata of Ellensburg Canyon of Washington state.^[14]

Paulownia macrofossils have been recovered from the late Zanclean stage of the Pliocene sites in Pocapaglia, Italy^[16] and Paulownia caucasica macrofossils have been recovered from strata of the Serravallian stage of the Miocene in Georgia in the Caucasus region.^[17] It is believed that the climate then would have been suitable for the genus across the whole northern hemisphere.^[18]

In China, Paulownia (Chinese: 泡桐; pinyin: pāotóng) is popular for roadside planting and as an ornamental tree. Paulownia needs much light and does not like high water tables.

As a forestry crop, Paulownia are exacting in their requirements, performing well only in very well draining soil, with summer rainfall or availability of irrigation water.^{[citation needed]} Paulownia is extremely fast growing, increasing in height by up to 6 metres (20 ft) in one year when young. Some species of plantation Paulownia can be harvested for sawn timber in as little as five years. Once the trees are harvested, they regenerate from their existing root systems, earning them the name of the "Phoenix tree"^{[citation needed]} (that name is alternatively attributed to the belief that it is the only tree within which the phoenix will roost.)^[19]

Paulownia is also used in Chinese agroforestry systems because it grows quickly, its wood is light but strong, its flowers are rich in nectar, its leaves make good fodder for farm animals, it is deep-rooting, and it is late-leafing, and its canopy is sparse enough to allow crops below it get enough light to grow while being sheltered from the wind.^[20]

 

Paulownia is known in Japanese as kiri (桐), specifically referring to P. tomentosa; it is also known as the "princess tree". Paulownia is the mon of the office of prime minister, and also serves as the Government Seal of Japan used by the Cabinet and the Government of Japan (whereas the chrysanthemum is the Imperial Seal of Japan).^{[citation needed]} It is one of the suits in the card game hanafuda, associated with the month of November or December (some regions reverse the order of these two months).^[21]

Japan: An Illustrated Encyclopedia states:

Paulownia wood is very light, fine-grained, and warp-resistant. It is the fastest-growing hardwood. It is used for chests, boxes, and clogs (geta). The wood is burned to make charcoal for sketching and powder for fireworks, the bark is made into a dye. The silvery-grey wood is sliced into veneers for special visiting cards.^[22][23]

 

It is important in China, Korea, and Japan for making the soundboards of stringed musical instruments such as the guqin, guzheng, pipa, koto, and gayageum.^[7] More recently it is used as body material for low-cost electric guitars,^{[citation needed]} as the core for lightweight touring skis,^[24][25] and for surfboard cores.^[26] It is typically used in guitars as the core body, then laminated under a more durable wood.^{[citation needed]}

 

Tested and confirmed species:^[15]

Potential variety, hybrid, and synonym species:

 

Wikimedia Commons has media related to Paulownia and Paulownia fortunei.

 

Wikispecies has information related to Paulownia.

• Paulownia forestry information Archived 2011-08-24 at the Wayback Machine
• Paulownia Research Center in China (Shaanxi)
• Flora of China - Paulownia
• Paulownia trees.org
• silvatree.com: Paulownia forestry
• fadr.msu.ru: "Paulownia, the Tree of Choice in China"