Poplar (Liriodendron tulipifera)
The yellow poplar is also called the "tulip tree" because of its tulip-flower shaped leaves. It is one of the tallest (up to 120 feet!) and most distinctive eastern North American hardwood trees. Its long, arrow-straight trunk, which may be two to three feet in diameter, reaches high up into a small, oblong crown of branches and foliage. These tall, straight trees stand like supporting pillars for the very forest itself.
Bark and Leaves
The bark of a mature yellow poplar is dark gray and deeply furrowed into long, rough, interconnecting ridges that are separated by lighter gray fissures. The leaves are four to six inches in diameter with four lobes that are notched into the rough "tulip-flower" shape. The leaves are attached to their twigs and branches by long (five to six inch) petioles which allow the leaves to rotate very freely even in very light breezes.
The yellow poplar flowers in the early spring (late April to early May on the Nature Trail). The flowers are large, cup shaped and showy with six greenish-yellow and orange petals. They are found at the ends of the leafy twigs high up in the tree canopy (often you have to use binoculars to see them!). These beautiful flowers are pollinated especially by honey bees. The fruits which form from these pollinated flowers are cone-shaped masses of many, one to one and a half inch, narrow winged samara (seeds plus 'wings' to aid dispersal). These samara begin to be shed in the autumn and will continue to fall to the forest floor through the winter.
Poplar seedlings that form from these samara do not grow well in the shaded conditions of the forest floor. When sunny gaps form in the canopy, however, these seedlings will grow at an incredible rate. It only takes fifty years, for example, for a yellow poplar to reach its maximum 120 foot height.
Poplar Wood and Longevity
The soft wood of the yellow poplar makes it very valuable tree for making furniture, toys and musical instruments but it also limits the longevity and survival of individual trees and contributes to a rapid cycle of sun gap formation. Yellow poplar trunks are easily broken by strong winds. There are many examples of broken and fallen yellow poplars all along the Nature Trail. This process of wind break opens up sunny, canopy gaps for new yellow poplar seedlings. A yellow
poplar forest is in an almost continuous process of dynamic destruction and rapid re-growth.
The yellow poplar is found most typically in mixed hardwood forests (intermixed with oaks, hickories, American beech, maples, black cherry and basswood) but is also found in association with a number of conifers (including white pine and hemlock). The key to the persistence of the yellow poplar in these forest associations is not the permanence of the individual trees, but rather the speed and robustness of its re-growth and replacement.