How do we distinguish between weeds and plants that are not weeds? Can native plants become weeds? An understanding of plant growth and development is essential to understanding adaptations that enable invasive plant species to adversely affect the land and water quality of our environment.

Introducing weed identification into your curriculum is a good way to introduce basic plant biology. To identify plants, one must be able to identify the parts of a plant. An understanding of plant parts leads naturally to the topic of classification.

For decades, scientists have attempted to classify organisms to better understand their relationships and similarities. Swedish botanist Carolas Linnaeus (1707-1778) used structural similarity as the basis of his classification system. Binomial nomenclature, the naming of all living things according to a hierarchy of shared characteristics, and the associated dichotomous keys used for identifying species, stem from his original work. Scientists worldwide use binomial nomenclature as the basis for classifying organisms.

This unit focuses on the following topics:

Traditional classification systems are a part of all schools’ science curricula, explicitly described as an essential skill in the National Science Education Standards (NSES) and most state education standards. Use the lessons about classification to replace or supplement a school’s unit on classification.

After learning about the foundation of typical classification systems, students will have the necessary vocabulary and understanding of how scientists group organisms by similar characteristics as an aid to identifying them in the field.

Plant Parts and Their Functions – Identifies plant parts, describes their functions, and explains how parts of weeds provide adaptive advantages over other plants.

Weed Clue – Encourages the study of local weed species, includes learning common names and describing characteristics.

Weed Identification Relay – Introduces plant identification in a field setting.

Introduction to Dichotomous Keys – Sharpens observational skills by using two dichotomous keys and having students create their own dichotomous keys.

Picture a Weed – Introduces plant anatomy and vocabulary through the use of field guides and keys.

Alien Seed Bank – Explores the concept of a seedbank and teaches students how to describe plant growth and life cycles of plants.

From Seed to Shining Seed – Investigates parts of a plant and stages of plant development in greater detail.

Classified Information – Applies the principles of the modern classification system while having students learn about the details of a noxious weed of their choosing.

Pressing Matters – Explains how to build a plant press and collect, identify, and press weeds.