Tulip Tree (Liriodendron tulipifera)

The tulip poplar is not a poplar at all but is a member of the magnolia family. It gets its name from the tulip-shaped flowers that are green and yellow. It is the tallest Eastern hardwood and was prized by Native Americans as a favorite tree to use to make dugout canoes.

I. Appearance and Characteristics 

Liriodendron tulipifera—known as the tulip tree, American tulip tree, tulipwood, tuliptree, tulip poplar, whitewood, fiddletree, lynn-tree, hickory-poplar, and yellow-poplar—is the North American representative of the two-species genus Liriodendron (the other member is Liriodendron chinense), and the tallest eastern hardwood. It is native to eastern North America from Southern Ontario and possibly southern Quebec to Illinois eastward to southwestern Massachusetts and Rhode Island, and south to central Florida and Louisiana. It can grow to more than 50 m (160 ft) in virgin cove forests of the Appalachian Mountains, often with no limbs until it reaches 25–30 m (80–100 ft) in height, making it a very valuable timber tree. The tallest individual at the present time (2021) is one called the Fork Ridge Tulip Tree at a secret location in the Great Smoky Mountains of North Carolina. Repeated measurements by laser and tape-drop have shown it to be 191 feet 10 inches (58.47 m) in height. This is the tallest known individual tree in eastern North America.

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 United States (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 eastern North America, known in an extraordinary case to reach the height of 58.5 m (192 ft) with the next-tallest known specimens in the 52–54 m (170–177 ft) range. These heights are comparable to the very tallest known eastern white pines, another species often described as the tallest in eastern North America.

The trunk on large examples is typically 1.2–1.8 m (4–6 ft) in diameter, though it can grow much broader. Its ordinary height is 24–46 m (80–150 ft) and it tends to have a pyramidal crown. It prefers deep, rich, and rather moist soil; it is common throughout the Southern United States. Growth is fairly rapid.

The bark is brown, furrowed, aromatic and bitter. The branchlets are smooth, and lustrous, initially reddish, maturing to dark gray, and finally brown. The wood is light yellow to brown, and the sapwood creamy white; light, soft, brittle, close, straight-grained. Specific gravity: 0.4230; density: 422 g/dm3 (26.36 lb/cu ft).

Winter buds are 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 125–150 mm (5–6 in) 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, 40–50 mm (1+1⁄2–2 in) 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, 50 mm (2 in) 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 from many samaras which are dispersed by wind, leaving the axis persistent all winter. September, October.

II. How to Grow and Care

Sunlight

Tulip trees prefer full sun or partial sun. Full shade can stunt the tree’s growth and cause its leaves to turn brown. The sunnier the area where you plant your tulip tree, the better.

Temperature and Humidity

Tulip trees like a temperate climate, which is why they can typically be found in the eastern United States. While it prefers normal moisture levels, it can tolerate drought in locations with high humidity.

Watering

Naturally growing along stream banks, the tulip poplar requires good watering in well-drained soil. Failure to keep it moist can result in loss of foliage and weak wood. Gardeners should keep the tulip poplar reasonably moist to support its growth.

Soil

These trees prefer slightly acidic, well-drained, deep soil amended with plenty of compost. They can thrive, though, within a pH range of 5.0 to 8.0. Tulip trees can handle clay, sandy, or loamy soils as long as the soil doesn’t hold water too long.

Fertilizing

Tulip poplar does well with fertilization and can grow double its size with the use of diammonium phosphate compared to other non-fertilized plants. Young specimens of tulip poplar are best supported with granular, liquid, or stake fertilizers. Gardeners can fertilize twice a month after dormancy and once during summer time, but stop fertilizing prior to dormancy.

Pruning

Because tulip trees grow so fast, pruning is imperative in order to keep them shapely and controlled. Their large branches are not particularly sturdy and can pose a hazard. Remove dead or weak growth in late winter and early spring, and do a thorough thinning every few years.

Propagation

Cuttings 

If you choose not to purchase your tulip tree from a nursery, you can instead propagate one using cuttings from a mother tree by following these steps:

• Take cuttings in the fall, selecting branches that are at least 18 inches or longer. Cut the branch just outside of the swollen area where it attaches to the tree.
• Place the cuttings in a bucket of water with rooting hormone added, following the directions on the label.
• When you’re ready to propagate, line a planter bucket with burlap and fill it with potting soil. Plunge the cut end of the branch approximately eight inches into the soil, then cover the cutting with plastic to hold in the humidity.
• Place the bucket in a protected area that gets bright, indirect light. Check for root development a few weeks later. Your tulip tree should be ready for transplanting by spring.

Seed

Though it is uncommon to grow a tulip tree from seed, it can be done if you have the patience. You can harvest seeds in the fall, after the pods have dropped from the tree. You can’t miss the seed pods since they look like little dried cone-like tulip flowers. Take these steps:

• When the pods are a light tan, harvest them before the seeds become separated. Dry the pods for a few days and then the seeds (that look like little wings to help them fly through the air) will begin to separate.
• Stratify moistened seeds in a refrigerator or other chilled space for 60 to 90 days to create a period of dormancy.
• Put the seeds into seedling pots filled with potting mix that is a bit acidic. Bury the seeds with a thin layer of soil, but don’t just scatter them across the top of the soil.
• Keep soil moist until the spring when you can plant the seedlings in their permanent spot outdoors.

Pests and Diseases

Common Pests

Tulip trees attract tulip tree scales and tulip tree aphids. Their feeding produces honeydew,1

Tulip Tree Aphids and Scales. NC State University Cooperative Extension.

 which can lead to sooty mold.2 These pests are temporary and rarely require control measures.

Common Problems With Tulip Trees

This tree is relatively low-maintenance. But they do present a few problems. Keep an eye out for some of these common issues:

Breakage

The wood of the tulip tree is very soft and the twigs, limbs, and branches are prone to breakage, especially in a windy location.

Litter and Sap

Tulip trees can be very messy, as their flower petals will litter the area below just after blooming, which is not ideal for locations like sidewalks and street areas. The trees are also notorious for dropping sticky sap, so avoid planting a tulip tree near an area where cars will be parked—it’s no fun trying to remove the sap from a car windshield.

Not Flowering

Your tulip tree may not flower if it is young. If a mature tree that is older than 15 years old is not flowering, it may be because your climate is too hot and dry, your soil is too compacted and not enough water is reaching the roots, or the tree is planted too deep, which buries the root collar and affects blooming.

III. Uses and Benefits 

• In landscape

Tulip trees make magnificently shaped specimen trees, and are very large, growing to about 35 m (110 ft) 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. In the wild it is occasionally seen around serpentine outcrops. 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 Magnoliaceae 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 12 m (40 ft) in height with no branches within reach of humans standing on the ground.

• Honey

Nectar is produced in the orange part of the flowers. The species is a significant honey plant in the eastern United States, yielding a dark reddish, fairly strong honey unsuitable for table honey but claimed to be favorably regarded by some bakers One 20-year-old tree produces enough nectar for 4 pounds (1.8 kg) of honey.

• Wood

hough not a poplar at all, the soft, fine-grained wood of tulip trees is known by that name (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 wood beams.

• Arts

The tulip tree has been referenced in many poems and the namesakes of other poems, such as William Stafford’s “Tulip Tree.” It is also a plot element in the Edgar Allan Poe short story “The Gold-Bug”.

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 sculptors such as Wilhelm Schimmel and Shields Landon Jones.