Plants Classification

Annual, Biennial, and Perennial
Plants fit into various classifications that relate to their life cycles, characteristics, features, and uses. First, plants can be annuals, biennials, and perennials based on their life cycles. Annual plants perform their entire life cycle from seed, vegetative growth, and flower to death within a single growing season. Whereas biennials grow in 2 years. In the first year, they grow vegetatively and overwinter. And in the following year, aside from growing vegetatively, they grow flowers and fruit, then die. Perennial plants live for more than 2 years. Generally, the top portion of perennials dies each autumn or winter and returns the following spring from the same root system. They grow year after year until full maturity is reached. However, this kind of classification is not absolute as one plant can be annual and perennial depending on where it grows. For example, geraniums would behave as an annual in Ontario, Canada whereas a perennial in Florida, US.
Below are some popular plants for each category.
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Annuals: Zonal geraniums, Morning glory, Fibrous begonias, Sweet allysum
Biennials: Viola cornuta 'Blue Perfection'
Perennials: Hosta, Echinacea purpurea (Purple coneflower), Astilbe (Astilbe species), Leucanthemum x superbum (Shasta daisy)

 

Source: GROW Training Program Presentation: "Intro to Botany and Plant ID", Zonal geraniums, Morning glory, Sweet allysum, Fibrous begonias (From the top left to clockwise)

 

Woody plants vs. Herbaceous plants
Plants can also be classified into woody plants and herbaceous plants. Woody plants have stems with a rigid outer surface whereas herbaceous plants don’t have any woody growth and the stems remain flexible throughout their lives. There are two kinds of woody plants: trees and shrubs. Generally, a tree grows taller than 13 feet (about 4 meters) and has one central stem with a distinct canopy. Whereas a shrub grows less than 13 feet and usually has more than one stem emerging from the bottom of the plant.
 
Deciduous plants vs. Evergreen
Another way of classifying plants is to see whether the leaves fall off or not during autumn. If the leaves fall off in autumn, then it’s a deciduous plant. It can take the form of a tree or a shrub. Flowering trees or shrubs are also included in deciduous plants. In contrast, there is an evergreen which has leaves that remain attached to the plant all year-round. An evergreen can be a tree or a shrub. Take note that the needles of evergreens can fall naturally. It’s not that evergreens keep their needles forever. While some evergreen plants are referred to as conifers, not all conifers are evergreen; there are deciduous conifers whose needles fall off during autumn. Dawn Redwood (Metasequoia glyptostroboides) and European Larch (Larix decidua) are examples of deciduous conifers. There is another thing to take note of. Not all evergreens have needles. Some of them have broadleaf and they are called broadleaf evergreens. Examples are Rhododendron and Boxwood.

Rhododendron - Azalea 'Elsie Lee'

 

 

Other Plants Classifications

We can classify plants differently according to their growing habits and characteristics. A vine is a plant with stems that cannot support themselves. So, they use other plants or objects such as trellises to rise above the ground. Low-lying plants with a creeping habit are groundcover. They can cover sections of the ground with minimal maintenance. A daylily and a creeping juniper are examples of the groundcover. A grass is a large group of monocotyledonous plants that have narrow leaves, hollow stems, and clusters of very small flowers. Grasses include turf grasses, bamboo, and ornamental grasses. Houseplants & Indoor flowering plants refer to tropical plants that can grow year-round indoors. Tropical, cacti, succulents, and flowering indoor plants are included in this category. Water plants are plants that live and grow in the water. They can be floating or rooted in pots or soil as well. Lastly, edible plants are plants that are grown for home production of fruit, vegetables, and herbs. They can be annual, perennial, trees, or shrubs.

 

​<Reference>
Landscape Ontario, GROW Training Program: “Introduction to Botany and Plant ID”
Landscape Ontario, Garden Centre Introductory Horticultural Training Videos