Horticulture Science

Lesson 6

Classifying Ornamental Plants

Interest Approach

Ask students to list as many plants as they possibly can in two or five minutes. (An interesting side activity is to ask them to list as many animals as possible in one minute. Notice that many more animals are listed on most student papers.) Begin a discussion on what types of plants were listed. Are they monocots or dicots, deciduous or evergreen, annual or perennial? (With the side activity, are they mammals, birds, reptiles, amphibians, or fish?)

Interest Approach

cont.

Why do students know more animals than plants? Why are students better able to classify animals than plants? Is it because of parents’ lack of plant knowledge or weaknesses in the educational system? Go around the room from student to student asking each to name one plant with which he or she is familiar. Immediately classify each plant as a fern, gymnosperm, or angiosperm (and whether each angiosperm is a monocot or a dicot). After each student has had a turn, allow the class to make observations as to which types of plants are the

most familiar and common.

Student Learning Objectives

•Discuss the classification and

naming of plants.

•Distinguish the major groups of

plants.

•Contrast the classification of

plants by life cycle.

Terms

• angiosperms • annuals • biennials • binomial nomenclature • bryophytes • conifer • cotyledon • cultivar

Terms

• deciduous • dicots • evergreen • ferns • genus • gymnosperms • herbaceous • monocots

Terms

• morphology • perennial • species • taxonomy • variety • vascular plants

How are plants classified and named?

• The branch of biology that deals with identifying and naming organisms is taxonomy.

• Plants are classified based on the similarities of their characteristics. • Plant taxonomists compare flowering patterns, stem and leaf structures, life cycles, genetic similarities, and many other characteristics in determining which plants are the most closely related. • The study of the form or shape of organisms or parts of an organism is called morphology.

How are plants classified and named?

• Taxonomists use categories to group the plants. • The categories, from general to specific, are: Kingdom, Division (Phylum), Class, Order, Family, Genus, Species, Variety, and Cultivar. • All plants are in the Kingdom Plantae. Vascular plants (plants with tissue specialized for conducting materials) are in the Division (Phylum) Tracheophyta.

How are plants classified and named?

• Plants are named using a system called binomial nomenclature. • This classification system was developed by Carolus Linnaeus and uses Latin terms as scientific names for plants. Carolus Linnaeus, the

'father of modern taxonomy'

How are plants classified and named?

• Even though each plant is given at least seven names, it is commonly referred to by two scientific names. • The two names used for the scientific names of plants are the Genus name, which is always capitalized, and the species name, which is always lower case (e.g., Liriodendron tulipifera).

Common Names for Liriodendron tulipifera: Tuliptree, Tulip Magnolia, Tulip Poplar, Yellow Poplar, Whitewood

How are plants classified and named?

• The genus is a group of plants that are very similar to each other.

• The species is a group of plants that are so similar that they usually mate freely with each other in the wild.

• Plants are also called by common names, but those names are specific and are based on language and geographic location.

How are plants classified and named?

• For instance, Liriodendron tulipifera is known in the United States as the yellow poplar, tulip poplar, tulip magnolia, whitewood, and tulip tree. • Although the tulip tree may be known by many common names in the United States, the plant is recognized as Liriodendron tulipifera everywhere on Earth.

How are plants classified and named?

• Sometimes cultivated plants within a species show a significant difference from other plants in the species. • These plants are called a variety. The difference is inherited from the previous generation through sexual reproduction. • The variety is written in lower case, underlined or italicized, and follows the specific epithet. • A variety of Colorado spruce with bluish needles is written as Picea pungens var. glauca or

Picea pungens glauca.

How are plants classified and named?

• Another group important to the horticulture industry is cultivar. • Cultivars have distinguishing characteristics from the other plants in the species, but cultivars do not transfer those characteristics to offspring through sexual reproduction.

• Cultivars are propagated by selective hybridization or asexual means. • A cultivar of red maple is written as follows: Acer rubrum, also known as “October Glory.”

What are some ways that we can put plants into groups?

• The plant kingdom has become successful all over the Earth by adapting to a wide variety of different conditions and niches. • The following are some of the major plant groups.

What are some ways that we can put plants into groups?

• Bryophytes are plants that are classified in the Phylum Bryophyta.

• These are nonvascular plants such as mosses and liverworts. • They tend to live in damp places and are very limited in size due to the lack of conducting tissue.

What are some ways that we can put plants into groups?

• Ferns are vascular plants that reproduce by spores. • Some people call them the amphibians of the plant world because they are dependent on water for their sperm to swim through during reproduction. • Ferns have no true leaves but have fronds, which have a double purpose of food production and spore formation.

• Fronds tend to unfold from the center of the plant, causing the newest fronds to be called “fiddlehead.”

What are some ways that we can put plants into groups?

• Gymnosperms are plants that reproduce with seeds that lay naked on scales.

• Most gymnosperms reproduce using a structure called a cone. • Any gymnosperm that reproduces by cone is called a conifer. • Examples include pines, spruces, and cedars.

What are some ways that we can put plants into groups?

• Conifer leaves are specialized to be either needles or scales. • Most conifers are evergreen, holding leaves all year. • But some are deciduous, dropping leaves in the winter. •An example is the bald cypress.

What are some ways that we can put plants into groups?

• Angiosperms are seed plants whose seeds develop within a fruiting body.

• Angiosperms all reproduce by flowers, although many flowers are very small and not showy. • So if any plant has flowers, it is in the Angiosperm group. • There are two types of Angiosperm.

What are some ways that we can put plants into groups?

• Monocots are plants that have a single cotyledon or seed piece. • Monocots have flower parts in multiples of three, parallel venation on their leaves, stems with scattered vascular bundles, and narrow leaves. • Examples include grasses, sweet corn, and lilies.

What are some ways that we can put plants into groups?

• Dicots are plants with two cotyledons in their seeds. • They have flower parts in multiples of four or five, netted veins, and stems that are organized in a ring pattern. • They have broad leaves and include roses, petunias, and geraniums.

What are some ways that we can put plants into groups?

How are plants classified by life cycle?

• Plants are often classified based on their life cycles. • Gymnosperms and angiosperms reproduce by seed, of course, but there are different strategies for passing on that seed to future generations of plants.

How are plants classified by life cycle?

• Plants that complete their life cycle within one year or one growing season are called annuals. • Seeds of annuals germinate, produce leaves and roots, flower, produce seed, and then die, all in less than a year.

How are plants classified by life cycle?

• Many of our crops and garden plants are annuals.

• Corn, soybeans, rice, wheat, potatoes, and tomatoes are examples of annual food crops.

• Petunias, impatiens, marigolds, and zinnias are examples of garden annuals.

• Many plants that are considered weeds (i.e., ragweed, pigweed, lambsquarter, and crabgrass) are annuals, too.

How are plants classified by life cycle?

• Biennials are plants that normally require two growing seasons to produce flowers and seed before dying. • In the first growing season, biennials grow vegetatively. • In the fall, they go dormant and rest until the following spring. • During the winter months, they receive a required cold treatment.

How are plants classified by life cycle?

• Growth is resumed in the spring of the second season. • The plants bolt, flower, produce seed, and die. • This group of plants is fewer in number than the other two groups. • Some examples include hollyhock, Sweet William, parsley, beets, and carrots.

How are plants classified by life cycle?

• Technically, a perennial is a plant that has a life cycle of more than two growing seasons. • It may take perennial plants a few years to many years to reach reproductive maturity. • Woody perennials may flower and produce seeds every year for many years. • They may be woody like trees and shrubs or herbaceous.

How are plants classified by life cycle?

• The shoots of herbaceous perennials typically die back to the ground each winter. • The roots and crowns of herbaceous perennial plants survive and send up new shoots in the spring. • Strawberries and asparagus are herbaceous perennials.

How are plants classified by life cycle?

• Woody perennial plants produce secondary growth that persists year after year.

• Secondary growth gives the plants the ability to grow in girth and height. • During the winter months, they go dormant. • Plant growth resumes in the spring. • Examples of woody perennial plants include apples, maples, oaks, almonds, and oranges.

How are plants classified by life cycle?

Review/Summary

•How are plants classified and

named?

•What are some ways that we can

put plants into groups?

•How are plants classified by life

cycle?