Paulownia

''Paulownia'' ( ) is a genus of seven to 17 species of hardwood tree (depending on taxonomic authority) in the family Paulowniaceae, the order Lamiales. They are present in much of China, south to northern Laos and Vietnam and are long cultivated elsewhere in eastern Asia, notably in Japan and Korea.

It was introduced to North America in 1844 from Europe and Asia where it was originally sought after as an exotic ornamental tree. Its fruits (botanically capsules) were also used as packaging material for goods shipped from East Asia to North America, leading to ''Paulownia'' groves where they were dumped near major ports. The tree has not persisted prominently in US gardens, in part due to its overwintering brown fruits that some consider ugly. In some areas it has escaped cultivation and is found in disturbed plots. Some US authorities consider the genus an invasive species, but in Europe, where it is also grown in gardens, it is not regarded as invasive.

The genus, originally ''Pavlovnia'' but now usually spelled ''Paulownia'', was named in honour of Anna Paulowna, queen consort of The Netherlands (1795–1865), daughter of Tsar Paul I of Russia. It is also called "princess tree" for the same reason.

''Paulownia'' trees produce as many as 20 million tiny seeds per year. However, the seeds are very susceptible to soil biota and only colonize well on sterile soils (such as after a high temperature wildfire). Well-drained soil is also essential. Successful plantations usually purchase plants that have been professionally propagated from root cuttings or seedlings. 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.

Trees can grow to maturity in under 10 years and produce strong, lightweight timber, good as firewood, with an even higher strength to weight ratio than balsa wood. Its density is low at around 0.28 kg/liter, although significantly higher than balsa's very low 0.16 kg/liter.

Morphology

''Paulownia'' is a genus of angiosperm trees, and one of the fastest growing trees in the world. ''Paulownia tomentosa'' can grow over tall and has (E see labeled image below) large heart shaped leaves ranging from wide and long with a long petiole. 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. 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 become 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 (B) inflorescences are terminal erect long panicles of ~ long flowers. (C) 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'' where the lobes are shorter than the calyx tubes. The corolla