Diggin' In: Magnificent tulip trees also have a mission

April 20, 2015

Spring brings out the best in flowering trees, especially native species like purplish-pink redbuds, white dogwoods and sweet bay magnolias, all relatively small trees.

Then, there’s the big daddy tulip tree, which can grow a magnificent 100 feet tall, according to Helen Hamilton, native plant expert and member of the John Clayton Chapter, Virginia Native Plant Society.

"The tallest tree in the forest is often the tulip tree, protruding over the canopy of other trees," she says.

"It usually grows over 100 feet tall with a trunk diameter of two to three feet, but in rich woods, it can reach nearly 200 feet in height and 10 feet in diameter. The largest trees of this species are in rich woods as in the Great Smoky Mountains National Park, with trees over 20 feet in circumference. Tulip trees in Virginia’s Shenandoah National Park are over 120 feet tall with diameters of over five feet."

Once the tulip tree goes through its juvenile stage and reaches adulthood in 15 to 20 years, it produces eye-catching yellow and white flowers. Tulip trees grow tall and straight, branching in a conical or pyramidal shape, according to Hamilton.

"In the forest, this tree is easily recognized by the trunk, which is free of branches for the first several feet, and the dark gray bark, often whitened in grooves," she says.

The tree is unique because no other tree has square-shaped leaves with four to six lobes, according to Hamilton. The leaves appear before any flowers, and persist through autumn, turning a brilliant yellow by October.

Blooming from April through June, depending on location and weather, the flowering period for each tree is only two to six weeks. Pollination must occur when the flowers are young; they are often receptive only for 12 to 24 hours. The plant produces large quantities of nectar for pollinating insects such as flies, beetles, honey bees and bumblebees, but they are not very efficient pollinators and many seeds do not develop. Tulip tree honey is a commercial product.

Tulip trees are long-timers, some having been found to be more than 300 years old, according to Hamilton.

"The flowers grow high in the canopy and are often seen only from the petals that fall on the pathways," she says.

"Tulip-shaped, the five petals of each flower are greenish-yellow with orange markings, and in the center there are many yellow-orange stamens and pistils, spirally arranged. The flowers are followed by narrow, upright cone-shaped fruit clusters of numerous, winged samaras. These dry fruits are often seen below the trees in early winter, and the seeds are eaten by squirrels, rabbits, mice and songbirds."

Tulip trees thrive in moist, well-drained soils and rich woods throughout the eastern United States to the Mississippi River, and grow wild in every county in Virginia, according to Gustav Hall, professor emeritus, College of William and Mary.

"The tree was introduced into Europe from Virginia by the earliest colonists and is also cultivated on the Pacific Coast," he says.

"It is often known as tulip-poplar and yellow poplar, and has been referred to as simply ‘poplar,’ but this name properly belongs to cottonwoods and their relatives in the willow family."

Commercially, the tree is an often-used hardwood with a fine, straight grain that’s easy to work and hard to split, according to Hamilton. It’s used for furniture, musical instruments and boat interiors, she says.

Several caterpillars, including locally known moths and butterfly species, love to munch on the leaves of the tulip tree, according to Hamilton.

"Common in our area is the tulip-tree beauty (Epimecis hortaria), an inchworm that develops into a moth with a striking black and white pattern," she says.

"Inchworms have no legs in the middle of their body, which is why they loop when walking."

Caterpillars of the eastern tiger swallowtail, (Papilio glaucus) also thrive on tulip tree leaves, according to Adrienne Frank, a Virginia master naturalist with the Historic Rivers Chapter.

"In the early summer of 2013, the population of caterpillars was very high, and as a result the top leaves of many tulip trees were eaten, leaving bare branches showing at the canopy of the trees," Frank says.

To spot an eastern tiger swallowtail, look for males that are yellow with dark "tiger" stripes, according to Brian Taber, president of the Coastal Virginia Wildlife Observatory. Females have two forms: one yellow like the male and the other black with shadows of dark stripes. Both female forms have a row of blue and yellow chevrons (lines or stripes in the shape of a V) and an iridescent blue wash over parts of the interior hind wing, he explains.

The butterflies reproduce two or three times during the season, which is why you see them in early spring, according to Hamilton. Each female lays a single egg on host plant leaves. As they develop, caterpillars eat the leaves and rest on silken mats on the upper surface of leaves. They overwinter as chrysalis.

Other host plants for these butterflies are wild cherry, sweet bay magnolia, willow and birch. Adults feed on the nectar of flowers from a variety of plants, including wild cherry, milkweeds and Joe-pye weed, says Hamilton.



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