Mad. Sq. Plant Profile: Hackberry
As part of our horticulture program, Madison Square Park Conservancy keeps phenological data on five species of trees located at Madison Square Park. Phenology is the study of cyclical events in the life cycles of plants and animals. For our horticulturists, this commonly comes in the form of noting when our plants break bud in the spring, when they flower, and when they set seed. This data lets you see the rhythm of the seasons acting on plants, and lets you see how natural cycles have changed over time. Phenology tracking is a vital tool in understanding the effects of climate change.
The first of several trees we keep phenological data on is the Hackberry: Celtis occidentalis. A native of the central and northeastern regions of the United States, the Hackberry is a popular tree in urban settings, especially in the midwest. Hackberries tolerate a wide range of adverse conditions, from soils that are too dry, too wet, or too clayey, very windy areas, and air pollution, which is part of what has made them so popular as street trees. They are one of the trees best suited to urban environments, and their resemblance to elm trees made them a common choice as replacement for dying elms following the onset of Dutch Elm disease. Hackberries are also quite winter hardy, able to tolerate temperatures down to USDA Hardiness Zone 2, where winters get down to between -40 and -50 degrees Fahrenheit. As the tree ages, it becomes more tolerant of adverse conditions; flood tolerance, for instance, is quite high in older trees whereas oversaturated soil can be fatal to young trees. Their ultimate size is dependant on their growth circumstances. They generally grow quickly even in less than ideal situations and mature at roughly 70’ tall, but in their preferred sites they can reach even larger, with exceptional trees reaching up to 110’. The hackberry is also decidedly short lived compared to other non-fruit trees, with an average lifespan of 150 years. While the Hackberry may not be an ornamentally stunning tree, they are tolerant to many of the conditions presented by climate change, only suffering significant threats by forest fires.
Interestingly enough, most of the names for hackberry refer to other plants. The genus name, Celtis, is the greek word for the jujube, which may have been the dangerous lotus plant said to be consumed by the Lotus Eaters Odysseus meets in The Odyssey. The common name, hackberry, is also a hand-me-down, descending from the scottish word for the cherry species Prunus padus, hagberry, which refers to either an association with witches, or via the scottish meaning of hag, swamps. Hackberries produce flowers and leaves concurrently, generally from late April to early May in the north. The flowers are insubstantial, but come autumn the fruits ripen from green to orange and finally to purple. The fruit is edible and slightly sweet, though it is only a thin portion covering the inner seed. The fruits are commonly eaten by birds before they fall to the ground, and this is one of the principal means of dispersal for the hackberry. Nutritionally speaking, hackberries are comparable to figs, having similar amounts of fiber and protein, and may contain antioxidants in their berries and antimicrobial compounds in their leaves.