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Tree to 55 m × 3 m dbh. Bark grey, fissured after about 25 years; craggy, browner, irregularly scaling ridges in old age. Crown usually taller than wide; trunk in the wild long and straight. Petiole 4–16 cm. Leaves usually flushing yellow-green, 5–15 x 5–18 cm, with (0)1–(5) pair(s) of shallow, forward-pointing lobes. Flowers in late spring (but from late January in some trees from central Florida); tepals 4 cm, the inner 6 overlapping to form a cup-shape and greenish-yellow with an orange blaze forming a ring around the flower on both sides. Fruit 7–9 cm; nutlets c. 6 mm, wing c. 4 cm long (Meyer 1997).
Distribution Canada Ontario United States Eastern and central states from central Florida to Vermont
Habitat Mixed forests, from sea level to 1500m in the Appalachian Mountains.
USDA Hardiness Zone 4-5
RHS Hardiness Rating H7
Conservation status Least concern (LC)
The American Tulip Tree is a popular plant for large gardens and parks around the temperate world: few trees so large and robust are so extravagantly ornamental. The leaves flutter on their long stalks as if to draw attention to their special shape, and the American name ‘Tulip Poplar’ reminds us of this, and of the tree’s timber qualities and rapid growth in the deep moist soils which it likes best. On poor dry or chalky soils it will survive rather than flourish. In Europe, it grows as far north as the Arboretum Mustila in Finland (Wikipedia 2018), but even in southern England only a few, younger specimens show the long, straight bole characteristic of the tree thriving in its native forests.
This must have been among the first American trees grown in England, though the details are lost; a tree at Waltham Abbey in Essex was measured at 29 m × 86 cm dbh in 1745 by Peter Collinson (Loudon 1843), and cannot have been much less than a hundred years old. The oldest surviving tree in Europe is probably one at Esher Place in Surrey whose dbh of 3.05 m in 2018 compares well with the largest wild trees, though a narrow fork from 2 m does inflate this; it is supposed to have been a gift from Bishop Henry Compton in the 1680s, an origin that its slow steady growth since 1906 tends to endorse (Tree Register 2018). The Welsh champion, on the Golden Grove estate in Carmarthenshire, has a very similar habit and by 2018 its dbh was 2.94 m; it was planted around 1767 (Loudon 1838).
The Tulip Tree copes better in the cool, Atlantic parts of Britain and Ireland than most broadleaves from the eastern United States, though it is clearly happiest in the warmer south and east. Multi-stemmed trees of 3.06 m dbh at 0.5 m grow as far northwest as at Molenan House in County Down, and of 2.43 m dbh at 0.5 m at Glenstal Abbey in County Limerick; a heavily burred tree planted around 1742 at The Hirsel (Scottish Borders) was 2.36 m dbh in 2003. A shapely tree, 29m tall, grows in woodland shelter at Arduaine on the Argyllshire coast, planted by James Arthur Campbell in the years after 1898. 24 trees measured in the UK and Ireland now exceed 2 m dbh, with about 400 of at least 1 m dbh; 27 exceeding 30 m in height. (Tree Register 2018).
In its native forests, Tulip Tree is the tallest broadleaf east of the Rocky Mountains, with a champion of 58.5 m climbed in 2011 in the Great Smoky Mountains National Park, North Carolina (Burnett 2012). Magnificent trees of 50 m tall grow in the native woodland area at Longwood Gardens in Pennsylvania (monumentaltrees.com 2018) and one of the most beautiful of any ornamental plantings is at nearby Swarthmore College, where the straight stems of Liriodendron rise from the stone and grass tiers of the amphitheatre used for college graduation ceremonies. Its yellow to dark brown timber, marketed as ‘Yellow Poplar’ and is easily worked, is valued for many purposes (Elias 1980).
The Tulip Tree is already among the tallest broadleaves in some warmer parts of Europe, with trees of 49.6 m recorded both at Villa Besana, Sirtori, near Milan, Italy in 2016, and at Sarrot near Pau in southwest France in 2018 (monumentaltrees.com 2018). Another of 46.4 m is the tallest tree in the National Botanic Garden at Meise in Belgium in 2016 (monumentaltrees.com 2018). A tree at Le Baraille in Albine, southern France, has a long hollowing bole with a dbh of 2.67 m in 2015 (monumentaltrees.com 2018), almost as impressive as any in the wild.
A sapling self-sown in a sandy walk at Longleat, Wiltshire around 1900 was noted by A. C. Forbes (Elwes & Henry 1906–1913); another seedling currently grows in the crook of a dead beech in Roath Park, Cardiff. It naturalises more readily in France (La Villette 2018).
Several variants have been named from the wild population with slightly differing leaf shapes and flower colours. More distinctive but not yet described scientifically is a coastal ecotype from the Carolinas, which is adapted to highly acid waterlogged conditions and can grow pneumatophores like a Taxodium. Its leaves have blunt lobes and often show a reddish cast on scarlet petioles (Parks et al. 1994). Another ecotype from east central Florida near Orlando has rounded lobing and is semi-evergreen; its small but brighter yellow flowers are carried from an earlier age and may open in the wild as early as January (Moriaty 2001; Wikipedia 2018).
‘Ardis’ is the nearest thing to a dwarf Tulip Tree, with small leaves to match; the main advantage is that the flowers (described as normal in size) will often be at head height. It was found by Mrs Ardis Sonneman and grown in her garden at Vandalia, Illinois (Hebb 1970). Plants in the Sir Harold Hillier Gardens have reached about 5 m after 30 years (Tree Register 2018), though a 1980s planting at Sandling Park in Kent rapidly reverted. ‘Compactum’ in the 1892 catalogue of Behnsch Nurseries, was presumably similar (Beissner, Schelle & Zabel 1903).
‘Aureomarginatum’ is one of the most robust and beautiful of variegated trees. The leaf shape is accentuated in spring by a broad, irregular daffodil-yellow margin, which deepens as the summer progresses to a green only slightly paler than that of the leaf’s centre. This fade makes the spring brilliance more breathtaking for its brevity, and allows the tree to grow almost as fast as the type; it seldom reverts, though the old tree at Gunnersbury Park in west London is an exception. The tallest known, planted in 1906 above the lake at Stourhead in Wiltshire, is one of the largest of variegated trees at 30 m by 2016 (The Tree Register 2018). A variegated clone of this kind was first noted (as ‘Luteo-marginatum’) by Louis van Houtte in 1869 (van Houtte 1869; Santamour & McArdle 1984). ‘Variegatum’ (Lavallee 1877) and ‘Aureo-variegatum’ (Jager & Beissner 1889) were probably the same tree, which is now sometimes sold in the United States as ‘Majestic Beauty’ (Monrovia Nursery, California) or ‘Flashlight’ (Lakeshore Garden Centres).
‘Contortum’, at the Arboretum de Segrez in 1877 Lavallee, A. (1877) has broad, rather twisted and undulant leaves. At the Bicton Park Botanical Gardens in Devon, it has made a neat, domed tree. ‘Crispum’, first described in 1869 Koch, K. (1869) and growing in the Sir Harold Hillier Gardens in Hampshire and the Bluebell Arboretum in Derbyshire Tree Register, The (2018), is similar if not identical.
Michael Dirr Dirr, M.A. (2009) also describes ‘Tortuosum’, a tree supposedly with twisted branches, but says its most conspicuous feature is its contorted leaves: he believes that it is the same as ‘Contortum’.
A semi-dwarf form found as a seedling by Gursztyn Nursery, Braniewo, Poland; the original tree is 1.8m tall and wide after 15 years, with a neat habit. Unlike ‘Ardis’, the leaves are nearly typical in shape and size Hatch, L.C. (2015).
‘Fastigiatum’ is a sport with erect, twisting branches, stylishly slender in youth but broadening untidily in middle age and prone to weak forks at a low height, which probably means that, like most fastigiate trees, it will never prove long lived. Careful attention can at least ensure that it starts off with the type’s typically straight single bole and there are some good younger street trees in England, supplied as tall standards, despite the difficulties inherent in establishing Tulip Trees at this size. There is a (now ragged) avenue of this clone on London Road in Headington, Oxford, which although a good idea has not coped well with the vicissitudes of such a situation. The sport was first catalogued (as ‘Pyramidalis’) at the Arboretum de Segrez in 1877 (Lavallee 1877). ‘Arnold’, propagated from examples of ‘Fastigiatum’ at the Arnold Arboretum in Massachusetts, often seems to show a better central axis, though this may simply be due to the care taken by the nurseries supplying the tree.
Emerald CityTM (‘JFS-Oz’, raised by J Frank Schmidt in Oregon (Dirr 2009)) is a broader but more shapely clone, forming a narrowly oval crown on a good stem, and with dark glossy foliage.
‘Glen Gold’, raised in Australia (Dirr 2009), has uniformly yellow leaves fading to lime green. The leaves are unusually large, which combined with apparently low vigour makes for a rather gawky plant; although it has been sold by UK nurseries for more than a decade, the author has yet to see an established tree. A specimen planted in 1999 in the Bodenham Arboretum in Worcestershire under the name ‘Greengold’ has grown quite vigorously to 11 m (Tree Register, The (2008)); its unfolding leaves in April are slightly yellowish between the main veins, suggesting that, even if ‘Greengold’ were to have been a misprint for ‘Glen Gold’, some degree of reversion has also occurred.
Dirr (2009) also mentions ‘Tennessee Gold’ as a selection made by Don Shadow, saying it is a vivid colour that holds better than ‘Glen Gold’.
‘Heltorf’ was found near Dusseldorf by J.R.P. Hoey-Smith and planted by him at Arboretum Trompenberg Santamour, F. S. & McArdle, A. J. (1984). Its side-lobes are themselves three-lobed, representing an extreme in the natural variation found in this species.
‘Integrifolium’ was described in 1838 Loudon, J.C. (1838) as a variant with blunt or rounded lobes, a mutation that is quite frequent among Tulip Trees in the wild and in cultivation, while f. integrifolium was published by Georg Kirchner to describe trees which retain the rounded, scarcely lobed shape of the first true leaves of seedlings. A ninteenth century planting (now lost) at Kew grown as ‘Integrifolium’ had just the two terminal lobes, making the leaves shield-shaped, and the name is now applied to this form. The sponsorship of Liriodendron by the Samuel Storey Family Charitable Trust in 2017 was inspired by the existence of the British and Irish Champion Liriodendron tulipfera ‘Integrifolium’ at Settrington, which has long been in the Storey family affections. It had a dbh of 0.87 m in 2011 Tree Register, The (2018), and may be from the same source as the tree at Kew mentioned above.
‘Ramapoo’ is said by Dirr (2009) to be similar. Variants with reduced or blunter lobes are discussed under ‘Roodhaan’.
‘Little Volunteer’, raised by Alexander Neubauer at his nursery at Belvedere, Tennessee, in 2001 Dirr, M.A. (2009), grows slightly more freely than the dwarf Tulip Tree ‘Ardis’ but has a stronger central stem; its leaves are more deeply lobed.
‘Mediopictum’ (also in the catalogue of the Arboretum de Segrez in 1877 Lavallee, A. (1877)) is the negative of ‘Aureomarginatum’, with a central yellow splash or streak to the leaves (which often lack side-lobes). The yellow splash is often small and sometimes absent and the clone is not so showy, though the variegation fades less in summer; a 1984 planting at Bradenham Hall in Norfolk was 19 m tall by 2014 Tree Register, The (2018).
‘Purgatory’ is a recent variant sold by BlueBell Nursery and others BlueBell Nursery (2018), with a flame-like yellow streak or stippling in the leaf’s centre. ‘Aureo-pictum’ Lauche, W. (1880) may have differered, since the leaves were described as flecked with yellow; ‘Aureo-maculata’ Royal Botanic Gardens, Kew (1895) was presumably similar to this.
‘Roodhaan’, propagated from another tree at Arboretum Trompenberg in Holland, has deep but blunt lobes. The name (‘red hen’; frequently misprinted as ‘Roothaan’) presumably refers to the flowers, whose orange blaze is dark and extensive. The Victorian ‘Rubrum’ Jager, H. & Beissner, L. (1889) presumably carried flowers of similar colour.
The varietal name obtusilobum was published by Michaux in 1803 for trees like ‘Roodhaan’ which show blunt lobing; BlueBell Nursery BlueBell Nursery (2018) sells this variant ‘Rotundilobum’ (with flowers described as normal in colour). The latinate name suggests that ‘Rotundilobum’ is an old clone, though if so it was missed by Santamour and McArdle in their 1984 catalogue of cultivars Santamour, F. S. & McArdle, A. J. (1984).
Other selections made for flower colour include ‘Aureum’ (distributed by Mallet Court Nurseries, Somerset, until 2007) with brighter yellow flowers – a variant first described as ‘Flavum’ by Loudon Loudon, J.C. (1838). ‘Leucanthum’, sold by Booth and Sons to the Bad Muskau Arboretum before 1864 Petzold, E. & Kirchner, G. (1864) had nearly white flowers.
Variants with reduced or blunter leaf lobes, including ‘Rotundilobum’ are discussed under ‘Roodhaan’
‘Snow Bird’, selected by Elliot Groves of Stepping Stones Nursery, New Plymouth, New Zealand (N. Dunn, pers. comm. 2018), has a showy, creamy white margin to its leaves; young trees are rather upright. Similar forms (‘Argenteo-variegatum’) were known as early as 1889 Jager, H. & Beissner, L. (1889) and are still sold in Germany as ‘Albomarginatum’ by Garten Braunlein and Garten Punzmann. A young tree grown as ‘Albovariegatum’ was at Tregothnan in Cornwall in 1989 Tree Register, The (2018), but has since been lost.