Liriodendron tulipifera — known as the tulip tree, American tulip tree, tuliptree, tulip poplar, whitewood, fiddle-tree, and yellow poplar — is the Western Hemisphere representative of the two-species genus Liriodendron, and the tallest eastern hardwood. It is native to eastern North America from Southern Ontario and Illinois eastward across southern New England and south to central Florida and Louisiana. It can grow to more than 50 m (165 feet) in virgin cove forests of the Appalachian Mountains, often with no limbs until it reaches 25–30 m (80–100 feet) in height, making it a very valuable timber tree. It is fast-growing, without the common problems of weak wood strength and short lifespan often seen in fast-growing species. April marks the start of the flowering period in the southern USA (except as noted below); trees at the northern limit of cultivation begin to flower in June. The flowers are pale green or yellow (rarely white), with an orange band on the tepals; they yield large quantities of nectar. The tulip tree is the state tree of Indiana, Kentucky, and Tennessee.
The tulip tree is one of the largest of the native trees of the eastern United States, known to reach the height of 190 feet (58 m), with a trunk 10 feet (3 m) in diameter; its ordinary height is 70 feet (21 m) to 100 feet (30 m). It prefers deep, rich, and rather moist soil; it is common, though not abundant, nor is it solitary. Its roots are fleshy. Growth is fairly rapid, and the typical form of its head is conical.
The bark is brown, and furrowed. The branchlets are smooth, and lustrous, initially reddish, maturing to dark gray, and finally brown. Aromatic and bitter. The wood is light yellow to brown, and the sapwood creamy white; light, soft, brittle, close, straight-grained. Sp. gr., 0.4230; weight of cu. ft., 26.36 lbs.
- Winter buds: Dark red, covered with a bloom, obtuse; scales becoming conspicuous stipules for the unfolding leaf, and persistent until the leaf is fully grown. Flower-bud enclosed in a two-valved, caducous bract.
The alternate leaves are simple, pinnately veined, measuring five to six inches long and wide. They have four lobes, and are heart-shaped or truncate or slightly wedge-shaped at base, entire, and the apex cut across at a shallow angle, making the upper part of the leaf look square; midrib and primary veins prominent. They come out of the bud recurved by the bending down of the petiole near the middle bringing the apex of the folded leaf to the base of the bud, light green, when full grown are bright green, smooth and shining above, paler green beneath, with downy veins. In autumn they turn a clear, bright yellow. Petiole long, slender, angled.
- Flowers: May. Perfect, solitary, terminal, greenish yellow, borne on stout peduncles, an inch and a half to two inches long, cup-shaped, erect, conspicuous. The bud is enclosed in a sheath of two triangular bracts which fall as the blossom opens.
- Calyx: Sepals three, imbricate in bud, reflexed or spreading, somewhat veined, early deciduous.
- Corolla: Cup-shaped, petals six, two inches long, in two rows, imbricate, hypogynous, greenish yellow, marked toward the base with yellow. Somewhat fleshy in texture.
- Stamens: Indefinite, imbricate in many ranks on the base of the receptacle; filaments thread-like, short; anthers extrorse, long, two-celled, adnate; cells opening longitudinally.
- Pistils: Indefinite, imbricate on the long slender receptacle. Ovary one-celled; style acuminate, flattened; stigma short, one-sided, recurved; ovules two.
- Fruit: Narrow light brown cone, formed by many samara-like carpels which fall, leaving the axis persistent all winter. September, October.
The leaves are of unusual shape and develop in a most peculiar and characteristic manner. The leaf-buds are composed of scales as is usual, and these scales grow with the growing shoot. In this respect the buds do not differ from those of many other trees, but what is peculiar is that each pair of scales develops so as to form an oval envelope which contains the young leaf and protects it against changing temperatures until it is strong enough to sustain them without injury. When it has reached that stage the bracts separate, the tiny leaf comes out carefully folded along the line of the midrib, opens as it matures, and until it becomes full grown the bracts do duty as stipules, becoming an inch or more in length before they fall. The leaf is unique in shape, its apex is cut off at the end in a way peculiarly its own, the petioles are long, angled, and so poised that the leaves flutter independently, and their glossy surfaces so catch and toss the light that the effect of the foliage as a whole is much brighter than it otherwise would be.
The flowers are large, brilliant, and on detached trees numerous. Their color is greenish yellow with dashes of red and orange, and their resemblance to a tulip very marked. They do not droop from the spray but sit erect. The fruit is a cone two to three inches long, made of a great number of thin narrow scales attached to a common axis. These scales are each a carpel surrounded by a thin membranous ring. Each cone contains sixty or seventy of these scales, of which only a few are productive. These fruit cones remain on the tree in varied states of dilapidation throughout the winter.
One of the largest and most valuable hardwoods of eastern North America, it is native from southern New England and New York westward to southern Michigan, and south to Louisiana and northern Florida. It is found sparingly in New England, it is abundant on the southern shore of Lake Erie and westward to Illinois. It extends south to north Florida, and is rare west of the Mississippi River, but is found occasionally for ornamentals. Its finest development is in the Southern Appalachian mountains, where trees may exceed 170 feet in height.
Liriodendron tulipifera is generally considered to be a shade-intolerant species that is most commonly associated with the first century of forest succession. In Appalachian forests, it is a dominant species during the 50–150 years of succession, but is absent or rare in stands of trees 500 years or older. On mesic, fertile soils, it often forms pure or nearly pure stands. It can and does persist in older forests when there is sufficient disturbance to generate large enough gaps for regeneration. Individual trees have been known to live for up to around 500 years.
All young tulip trees and most mature specimens are intolerant of prolonged inundation; however, a coastal plain swamp ecotype in the southeastern United States is relatively flood-tolerant. This ecotype is recognized by its blunt-lobed leaves, which may have a red tint. Liriodendron tulipifera produces a large amount of seed, which is dispersed by wind. The seeds typically travel a distance equal to 4-5 times the height of the tree, and remain viable for 4–7 years. The seeds are not one of the most important food sources for wildlife, but they are eaten by a number of birds and mammals.
Vines, especially wild grapevines, are known to be extremely damaging to young trees of this species. Vines are damaging both due to blocking out solar radiation, and increasing weight on limbs which can lead to bending of the trunk and/or breaking of limbs.
Taxonomy and naming
Originally described by Linnaeus, Liriodendron tulipifera is one of two species in the genus Liriodendron in the magnolia family. The name Liriodendron is Greek for "lily tree". It is also called the tuliptree Magnolia, or sometimes, by the lumber industry, as the tulip poplar or yellow poplar. However, it is not closely related to true lilies, tulips or poplars.
The tulip tree has impressed itself upon popular attention in many ways, and consequently has many common names. In areas near the Mississippi River it is called a poplar largely because of the fluttering habits of its leaves, in which it resembles trees of that genus. The color of its wood gives it the name Whitewood. Native Americans so habitually made their dugout canoes of its trunk that the early settlers west of the Appalachian Mountains called it Canoewood. It is sometimes called "fiddle tree," because its peculiar leaves, with their arched bases and in-cut sides, suggest the violin shape. The external resemblance of its flowers to tulips named it the Tulip-tree. In their internal structure, however, they are quite different. Instead of the triple arrangements of stamens and pistil parts, they have indefinite numbers arranged in spirals.
East Central Florida ecotype
Parts of east-central Florida near Orlando have an ecotype with similar-looking leaves to the coastal plain variant of the Carolinas; it flowers much earlier (usually in March, although flowering can begin in late January), with a smaller yellower bloom than other types. This east central Florida ecotype seems to have the best ability to tolerate very wet conditions, where it may grow short pencil-like root structures (pneumatophores) similar to those produced by other swamp trees in warm climates. Superior resistance to drought, pests and wind is also noted. Some individuals retain their leaves all year unless a hard frost strikes. Places where it may be seen include Dr. Howard A. Kelly Park, Lake Eola Park, Spring Hammock Preserve, and the University of Central Florida Arboretum.
Cultivation and use
Liriodendron tulipifera grows readily from seeds, which should be sown in a fine soft mould, and in a cool and shady situation. If sown in autumn they come up the succeeding spring, but if sown in spring they often remain a year in the ground. Loudon says that seeds from the highest branches of old trees are most likely to germinate. It is readily propagated from cuttings and easily transplanted.
Tulip trees make magnificently shaped specimen trees, but are very large, growing to about 35 m in good soil. They grow best in deep well-drained loam which has thick dark topsoil. They show stronger response to fertilizer compounds (those with low salt index are preferred) than most other trees, but soil structure and organic matter content are more important. The southeastern coastal plain and east central Florida ecotypes occur in wet but not stagnant soils which are high in organic matter. All tulip trees are unreliable in clay flats which are subject to ponding and flooding. Like other members of the Magnolia family, they have fleshy roots that are easily broken if handled roughly. Transplanting should be done in early spring, before leaf-out; this timing is especially important in the more northern areas. Fall planting is often successful in Florida. The east central Florida ecotype may be more easily moved than other strains because its roots grow over nine or ten months every year—several months longer than other ecotypes. Most tulip trees have low tolerance of drought, although Florida natives (especially the east central ecotype) fare better than southeastern coastal plain or northern inland specimens.
It is recommended as a shade tree. The tree's tall and rapid growth is a function of its shade intolerance. Grown in the full sun, the species tends to grow shorter, slower, and rounder, making it adaptable to landscape planting. In forest settings, most investment is made in the trunk (i.e., the branches are weak and easily break off, a sign of axial dominance) and lower branches are lost early as new, higher branches closer to the sun continue the growth spurt upward. A tree just 15 years old may already reach 40 feet in height with no branches within reach of humans standing on the ground.
- 'Ardis' - shorter, with smaller leaves than wild form. Leaves shallow-lobed with waist near top.
- 'Arnold' - narrow, columnar crown; may flower at early age.
- 'Aureomarginatum' - variegated form with pale-edged leaves; sold as 'Flashlight' or 'Majestic Beauty'.
- 'Fastigatum' - similar form to 'Arnold'.
- 'Florida Strain' - blunt-lobed leaves, fast grower, flowers at early age.
- 'Integrifolium' - leaves without lower lobes.
- 'JFS-Oz' - somewhat compact oval form with straight leader, leaves dark and glossy; sold as 'Emerald City.'
- 'Leucanthum' - flowers white or nearly white.
- 'Little Volunteer' - almost as diminutive as 'Ardis.' Leaves more deeply lobed than 'Ardis' with waist in middle.
- 'Mediopictum' - variegated form with yellow spot near center of leaf.
- 'Roothaan' - blunt-lobed leaves.
Liriodendron tulipifera has been introduced to many temperate parts of the world, at least as far north as Sykkylven, Norway.
This tree species is a major honey plant in the eastern United States, yielding a dark reddish, fairly strong honey which gets mixed reviews as a table honey but is favorably regarded by bakers. Nectar is produced in the orange parts of the flowers. Some specimens may be poor nectar producers simply because they have relatively little orange in their flowers. On the other hand, the east central Florida ecotype may secrete copious amounts of nectar (see the images of its flowers below).
The soft, fine-grained wood of tulip trees is known as "poplar" (short for "yellow poplar") in the U.S., but marketed abroad as "American tulipwood" or by other names. It is very widely used where a cheap, easy-to-work and stable wood is needed. The sapwood is usually a creamy off-white color. While the heartwood is usually a pale green, it can take on streaks of red, purple, or even black; depending on the extractives content (i.e. the soil conditions where the tree was grown, etc.). It is clearly the wood of choice for use in organs, due to its ability to take a fine, smooth, precisely cut finish and so to effectively seal against pipes and valves. It is also commonly used for siding clapboards. Its wood may be compared in texture, strength, and softness to white pine.
Used for interior finish of houses, for siding, for panels of carriages, for coffin boxes, pattern timber, and wooden ware. During scarcity of the better qualities of white pine, tulip wood has taken its place to some extent, particularly when very wide boards are required.
It also has a reputation for being resistant to termites, and in the Upland South (and perhaps elsewhere) house and barn sills were often made of tulip poplar beams.
Another form of art that the tulip tree is a major part of is wood carving. The tulip poplar can be very useful and has been one of the favorite types of trees for wood carving by sculptures such as Wilhelm Schimmel and Shields Landon Jones.
- The Queens Giant, a tulip tree that is the oldest living thing in the New York Metropolitan area (350–450 years old, 40 m / 134 feet tall)
- Spathodea campanulata, often known as the African tulip tree, an unrelated plant in a separate family (Bignoniaceae).
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