Plant taxonomy is a branch of the sciences which is concerned with describing, identifying, categorizing, and naming plants. Several different systems are used to taxonomize plants, with the most familiar being the Kingdom, Phylum, Class, Order, Family, Genus, Species hierarchy. Biologists who work with plants utilize plant taxonomy on a daily basis to order and make sense of the plants they work with, and to effectively communicate information to other biologists.
Taxonomy has very old roots. Simply by naming things, humans are starting to taxonomize them, as names allow people to distinguish between various items they interact with. For example, freezers and refrigerators look similar and have similar functions, but they are also very different, which is why two different terms are used to refer to these common appliances. In biology, taxonomy is especially important because it can be used to make sure that people are talking about the same thing, and to uncover similarities, differences, and information about genetic inheritance.
When plants are in the same genus, for example, it means that they are closely related, and their common ancestor is not far away. Plants in the same class, on the other hand, are more distantly related, although they are more closely related than plants in the same phylum. Each step along the hierarchy is designed to more precisely narrow down the identification of a plant.
Whenever researchers think that they have found a new plant species, they try to fit it into the existing plant taxonomy system by using its characteristics to classify it. Along the way, they may learn that the plant has already been discovered, described, and named. Plant taxonomy is also very fluid; plants may be moved around as people learn more about them, as for example when genetic testing reveals that two plants are actually the same species, or when testing shows that plants are more distantly related than biologists thought.
People also use plant taxonomy to identify known plants. People who are interested in wildflowers, for example, often carry around plant keys so that when they see a plant in the field, they can follow a series of prompts to find out what the plant is, and to learn more about it. The correct identification and classification of plants is also of interest to nurseries and gardeners. When a gardener walks in and asks for a “nasturtium,” for example, the nursery will not know if the gardener is referring to plants in the genus Nasturtium, or the plants in the genus Tropaeolum which are commonly known as nasturtiums, but if the gardener uses a scientific name from a recognized taxonomic system, the nursery will know exactly what the gardener is asking for.