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College Interns Count Emerging Invasives in Central Park


Our Horticultural Sciences interns work in Central Park for 10 weeks in the summer to learn about the many responsibilities that go into the care of an urban park. Through trainings in plant identification, site assessment, soil science, and sustainable design, they develop essential skills needed to manage an urban environment.

One perpetual challenge of urban horticulture is managing invasive species of plants. They keep our staff, volunteers, and interns busy almost every day and require consistent awareness. As part of our college interns’ Weeds and Invasive Plant Management training, we invited Daniel Atha of New York Botanical Garden and the Central Park Flora Project to share about emerging invasive species or species that are not yet officially designated as invasive, but have indicated invasive behavior in our region.

College interns counting invasives

Daniel’s research into emerging invasive species in New York shows that tea crabapple (Malus hupehensis), is likely more widespread than is currently documented. Tea crabapple reproduces by seed, is shade tolerant, and is dispersed by birds. A tree or shrub up to five meters tall, its bark is grey, with bronze and green leaves, it flowers in April or May for about a week, with fragrant pink or white blooms. A native of China, it is found in woodlands in the New York metropolitan region.

Tea crabapple collage

The college interns assisted Daniel in mapping distribution of tea crabapple in the North Woods by learning how to transect, or count, a species. This quantifying is crucial to tracking changes in abundance over time; in other words, counting plants in a particular area is important to keep track of the species’ reproduction and growth. Such information influences our management of Central Park.

To construct a transect, the interns used a measuring tape and rope to make a 100 meter line, marking regular intervals of 10 meters and creating ten plots of 100 square meters. They then formed additional plots with a frame made from PVC pipe, generating 100 smaller subplots within each of the ten larger plots. If the tea crabapple was found in one of the ten larger plots, a random number was generated with a smartphone app to count the number of individual tea crabapples in the subplot of that number. This method uses the predictive potential of scientific plant management research to identify how much of a threat the tea crabapple is right now.

College interns frame plots
College interns counting invasives

According to Daniel, tea crabapple will be “the little apple that ate the Big Apple” without careful management. His research and close collaboration with our Operations staff through the Central Park Flora Project, have allowed us to actively manage for this species. Our Woodlands team removes it throughout the Park’s woodlands and replaces it with beneficial native plants to allow for increased biodiversity and overall ecological health. In turn, we work to keep our next generation of park stewards informed of these current management issues through our career development programs, like the Horticultural Sciences College Internship and the ROOTS program, whose students removed dozens of tea crabapples in the North Woods this past spring.