Paul again! Part of my work here at Chippokes Plantation State Park is mapping out where different species of trees are located, with a special focus on finding the invasive ones. The most aggressive of these invaders in Chippokes is Ailanthus altissima, the Tree-of-Heaven. Originally from China, this tree was brought to America in 1784 by William Hamilton. It was planted due to the need for a shade tree that could survive the harsh conditions of urban life; “A Tree Grows in Brooklyn” refers to the Tree-of-Heaven. Unfortunately, it was realized too late that the flowers and twigs emit a foul odor, and the limbs are bare except for explosions of leaves at the tips, lending a ‘Dr. Suess’ look to its canopy.
The leaves of Ailanthus resemble our local sumacs and walnuts but can be distinguished by several characteristics. The trunk of Ailanthus grows much taller than any sumac, reaching a height of up to 80 feet, but with smooth bark, instead of the furrows and ridges that walnuts have. The leaves of Ailanthus have an entire, or smooth, edge and an asymmetrical base. Conversely, the edges of walnut and sumac leaves are serrated. Lastly, Ailanthus bears yellow- green flowers in June, which give rise to pods called samara, allowing the Ailanthus to disperse about 325,000 windborne seeds. Chestnut and walnuts bear the very familiar nuts that bear the trees’ names.
Once established in an area, Ailanthus will begin to secrete chemicals into the soil, called allelochemicals, which inhibit the growth of seedlings from other trees, allowing tree-of-heaven to take over an area. Don’t think you can just cut it down, though. It’ll send out new growth, called sucker shoots, from the stump and roots. Spraying herbicide kills the leaves, but what you end up with is a stand of tall, skinny, red twigs, which will just try to put out leaves again.
The one saving grace is that Ailanthus is shade intolerant. Its seedlings have a hard time sprouting when underneath the canopy, restricting it to roadsides and clearings. This is a tree that is designed to take full advantage of temporary openings in a forest, usually caused when a tall tree falls, creating gaps where sunlight can reach the ground. Unfortunately for the park, the agricultural fields of the plantation are like an open invitation to the Ailanthus, and it is only by the continuous farming and the vigilance of our maintenance crews that its growth has been held in check, and in some places pushed back.