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Plant ID with the Dichotomous Key

Successful park management hinges on knowing what plants are in your landscape and what kind of care each plant needs to thrive. Accurate identification of a plant allows park managers to know whether they’re dealing with a native or invasive species, which can sometimes look very similar. Or it helps them differentiate between similar-looking species that may have very different irrigation needs.

The dichotomous key is a system for quick field identification of plants. Central Park Conservancy staff use Newcomb’s Wildflower Guide to identify wildflowers, flowering shrubs, and vines that grow in northeastern and north-central North America. No formal botanical training is needed to use the guide, making it ideal for any user. It follows a simple but precise key system based on the most easily seen features that make each species unique, and it is fully illustrated. Identification with the dichotomous key begins by answering five questions about the plant, related to flower type, plant type, and leaf type. The answers to the questions determine the plant group to which the specimen in question belongs, and the guide leads you to the page in the book where the plant and others similar to it are described. You complete the identification by matching your specimen to its description and illustration.

One example in Central Park that underscores the importance of accurate plant ID is the porcelain berry (Ampelopsis brevipedunculata). Porcelain berry grows throughout the Park and is an aggressive invasive plant that can quickly overwhelm native plants. Its vigorous vines outcompete trees and shrubs by reducing the availability of light, water, nutrients, and space. A deciduous, woody, perennial climbing vine, it spreads by seed. However, it looks remarkably similar to another vine also found in the north end of the Park: the native fox grape (Vitis labrusca). Recently discovered in the Park by the Central Park Flora Project, fox grape is beneficial to wildlife, serving as a pollinating plant for a variety of bee species and a source of food for other insects, birds, and mammals.

fox grape

Fox grape’s main differences from porcelain berry are its lack of lenticels and pith (the center portion of its stem) that is not continuous. Maintaining and nurturing the fox grape increases plant diversity in the Park and the region, whereas allowing porcelain berry to thrive actually reduces plant diversity. Doing so requires knowing which plant is which, and the dichotomous key is one aid in determining which plant is which.

Managing a large urban park that gets 42 million visits a year, as Central Park does, is a complex endeavor. One crucial component of this management is identifying plants. However, the Central Park Conservancy relies on a surprisingly simple tool to do it: the dichotomous key.

Newcomb's Wildflower Guide