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Owen Johnson (2022)
Johnson, O. (2022), 'Paulownia catalpifolia' from the website Trees and Shrubs Online (treesandshrubsonline.
A tall tree with a straight trunk in suitable conditions. Leaves often narrowly cordate (twice as long as broad), with dense stellate hairs beneath but glabrous above. Flowerhead usually less than 35 cm tall; cyme peduncle nearly as long at the pedicels. Calyx shallowly bell-shaped, lobed to less than half its length, glabrescent after flowering. Corolla light purplish with often dense purple spotting, the lower lip strongly ridged; narrowly tubular to funnel-shaped, 70–80 mm long but only 35 mm wide at the mouth. Seed capsule ellipsoid, 45–55 mm long, with stellate hairs then glabrescent; wall less than 3 mm thick and not woody. (Hong et al. 1998).
Distribution China Shandong (Zou Xian)
Habitat Low elevations; a pioneer species.
USDA Hardiness Zone 7
RHS Hardiness Rating H5
Conservation status Not evaluated (NE)
Paulownia catalpifolia is a species from the subtropical south of China which was only separated from its near ally P. elongata by T. Gong in 1976 (IPNI 2022). These species differ from the more northern P. tomentosa in being less pubescent (particularly the ripening seed-pod), and in bearing a calyx lobed to less than half its length (Hong et al. 1998). From P. elongata, P. catalpifolia is distinguished by its narrower, more tubular corollas and its leaves which can be significantly narrower than is typical for the genus (typically twice as long as they are broad). After a fast start, P. catalpifolia is less vigorous than P. elongata, but the slower-grown timber can command three times the price (Cathaia International 2022); it is now cultivated for its timber in China and has contributed its genes to a couple of today’s hybrid forestry clones, ‘H2F3’ and ‘H2F4’.
As is the case with most Paulownia species, widespread cultivation has obscured the original, wild distribution. The Flora of China (Hong et al. 1998) indicates that P. catalpifolia is only native to a small area in Shandong province, though other sources (Grimshaw & Bayton 2009) suggest a wider natural range.
Plants purporting to be P. catalpifolia became commercially available in the west around the start of the 21st century, but it is difficult to determine their sources (and authenticity). In 2006, seven Plant Finder nurseries were offering the plant (Royal Horticultural Society 2006), though by 2022 this number had shrunk to one (Royal Horticultural Society 2022). So far, the largest recorded example is the one planted by David Ewins in his UK National Collection near Bath, which he sourced from Fillans Plants in 2003 and which had reached 10 m × 28 cm dbh in 2022 (Tree Register 2022); this tree does not always show the very narrow leaves described by the Flora of China, and its flowers lack dense purple spotting on the throat. It is the most reliable flowering tree in the collection (D. Ewins pers. comm.).
Like other Paulownia species with a southerly distribution, the plants so far grown as P. catalpifolia in Europe and North America are hardier than might be expected, and more tolerant of cool and uncertain summers. An 8 m sapling at Christine Battle’s former Congrove Arboretum (also near Bath, in a warm part of England) was growing very fast in 2014 (Tree Register 2008). Another at the Arboretum de Segrez near Paris flowered as early as 2013 (Esveld Nursery 2022), and the species has also succeeded at the C.R. Keith Arboretum in North Carolina (USDA zone 7a) (Hatch 2021–2022).