| Paulownia | |
|---|---|
 | |
| Paulownia tomentosa | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Asterids |
| Order: | Lamiales |
| Family: | Paulowniaceae |
| Genus: | Paulownia Siebold &Zucc. |
| Species | |
Six to 17 species, including: | |
Paulownia (/pɔːˈloʊniə/paw-LOH-nee-ə) is a genus of seven to 17 species ofhardwood trees (depending on taxonomic authority) in the familyPaulowniaceae, the orderLamiales. The genus and family are native to east Asia and are widespread across China.[1] The genus, originallyPavlovnia but now usually spelledPaulownia, was named in honour ofAnna Pavlovna, queen consort of The Netherlands (1795–1865), daughter ofTsarPaul I of Russia. It is also called "princess tree" for the same reason.[2]
It was originally sought after as an exotic ornamental tree in Europe and Asia, and later introduced to North America in 1844. Its fruits (botanicallycapsules) were also used as packaging material for goods shipped from East Asia to North America, leading toPaulownia groves where they were dumped near major ports. The tree has not persisted prominently in US gardens, in part due to its overwintering brownfruits that some consider ugly.[3] In some areas it hasescaped cultivation and is found in disturbed plots. Some US authorities consider the genus aninvasive species,[4] but in Europe, where it is also grown in gardens, it is not regarded as invasive.
Paulownia trees produce as many as 20 million tiny seeds per year. However, the seeds are very susceptible tosoil biota and only colonize well on sterile soils (such as after a high temperaturewildfire). Well-drained soil is also essential. Successful plantations usually purchase plants that have been professionally propagated fromroot cuttings orseedlings.[5] Although seeds, seedlings, and roots of even mature trees are susceptible to rot, the wood is not and is used for boat building and surfboards.
Dimensionally stable and given its straight grain and light weight,Paulownia timber is extremely easy to work with and is reported to be resistant to decay, with good weathering characteristics.[6]
Trees can grow to maturity in under 10 years and produce strong, lightweight timber, good as firewood, and with an even higherstrength to weight ratio thanbalsa wood.[7] Its density is low at around 0.28 kilograms per liter (2.8 lb/imp gal),[8][7][9] although significantly higher than balsa's very low 0.16 kilograms per liter (1.6 lb/imp gal).[10][11]
Paulownia is a genus ofangiosperm 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)-longpetiole.[13] The leaves grow in oppositedecussate pairs, and as the nametomentosa suggests, are covered in hairs. The leaf margin can be toothed orentire and sometimes may be slightly lobed. They can be distinguished from common look-alike genera, such asCatalpa andCercis, by secondary and tertiaryvenation.[14] The leaves are late to come in on the tree and late to fall from the typicallydeciduousPaulownia. However, in tropical areas, the tree can be evergreen.
The leaves are often preceded by pale violet to purple-shaded tubular flowers, similar to afoxglove. Like most members of the Lamiales, the flowers arezygomorphic. Theinflorescences are terminal erect 15–30 centimetres (6–12 in)-longpanicles of ~5 centimetres (2 in) long flowers.[13] The thick, fusedcalyx is covered by a brown hairyindumentum, and the fused calyx tube is the same length as its calyx lobes, except inP. catalpifolia andP. elogata, in which the lobes are shorter than the calyx tubes.[15] Thecorolla has five fused lobes with a shorteradaxial bilobed lip, and a somewhat longerabaxial 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 asfloral guides to the top of the corolla tube.[13] Inside the corolla tube, and approximately halfway down, are fourstamen 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 shapedanthers then depositing pollen on the dorsal side of a variety of pollen-feeding insects.
The superiorbilocularovary, surrounded by the brown calyx, with itsstigma andstyle 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 speciesP. kawakamii, the stigma tip is slightly bilobed, which is a unique morphological characteristic distinguishingPaulownia from all of the Lamiales.[13] At the bottom of the ovary is anectary, 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, andloculicidaldehiscence 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 inNorth America, with fossilized leaves being found inTertiarystrata of Ellensburg Canyon ofWashington state.[14]
Paulowniamacrofossils have been recovered from the lateZanclean stage of thePliocene sites inPocapaglia,Italy[16] andPaulownia caucasica macrofossils have been recovered from strata of theSerravallian stage of theMiocene inGeorgia in theCaucasus region.[17] It is believed that the climate then would have been suitable for the genus across the whole northern hemisphere.[18]
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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 plantationPaulownia 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 Chineseagroforestry systems because it grows quickly, itswood is light but strong, itsflowers are rich innectar, itsleaves make goodfodder forfarm animals, it is deep-rooting, and it is late-leafing, and itscanopy is sparse enough to allowcrops below it get enoughlight to grow while beingsheltered from the wind.[20]
Paulownia is known inJapanese askiri (桐), specifically referring toP. tomentosa; it is also known as the "princess tree".Paulownia is themon of the office ofprime minister, and also serves as theGovernment Seal of Japan used by theCabinet and theGovernment of Japan (whereas thechrysanthemum is theImperial Seal of Japan).[citation needed] It is one of the suits in the card gamehanafuda, 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, andwarp-resistant. It is the fastest-growing hardwood. It is used forchests, boxes, and clogs (geta). The wood is burned to makecharcoal for sketching and powder forfireworks, the bark is made into adye. The silvery-grey wood is sliced into veneers for special visiting cards.[22][23]
Paulownia boxes calledtomobako (ともばこ) protect ceramic works and other fragile items during shipment and storage.[24] The lid of the box usually tied down with a flat ribbon called asanada-himo (真田紐). Japanese wardrobes calledtansu (箪笥) as well as much Koreanlacquerware is also made from the wood.
It is important in China, Korea, and Japan for making the soundboards of stringed musical instruments such as theguqin,guzheng,pipa,koto, andgayageum.[7] More recently it is used as body material for low-cost electric guitars,[citation needed] as the core for lightweight touring skis,[25][26] and for surfboard cores.[27] It is typically used in guitars as the core body, then laminated under a more durable wood.[citation needed]
is known inJapanese askiri (桐), specifically referring toP. tomentosa; it is also known as the "princess tree".P
Tested and confirmed species:[15]
Potential variety, hybrid, and synonym species:
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