A Brief Overview of Plant Life Cycles
Plant types are grouped by the growing seasons required to complete a life cycle. In general, plants are classified as Annual, Biennial, Perennial, or Ephemeral. Factors that determine the classification of a plant include location, reproduction, and environmental roles. The harvest times for most produce varies depending upon environmental factors.
Are those whose life cycle is completed over a year’s time. Annuals are usually planted in the spring, bloom in the summer, and seed just before their demise in the fall. Annuals can be separated into three additional groups based on the environmental temperatures in which they can thrive. These groups are:
• Hardy Annuals – which are able to withstand cold soil and hard frosts,
• Half – Hardy Annuals – which are still able to thrive in cold soil temperatures to a certain limit, and can usually withstand light frosts.
• Tender Annuals – cannot survive in freezing temperatures whatsoever.
Most vegetable and grain plants are annuals, but not all. Examples include Potatoes, Tomatoes, Broccoli, Cauliflower, and Melons.
Complete their life cycle over a two year growing period. Once sown, vegetative structures such as leaves, stems, and roots begin to grow and form a small rosete. Biennial plants will only produce these structures during the first year. After the first growing season, the tops of the plants will die back, leaving rootstock that will remain during the plant’s dormancy through the colder months. In the following growing season of the second year, biennials will flower, set seed, and finally complete their life cycle and perish in the fall of the second year. Examples of biennial plants include Beets, Cabbage, Carrots, Hollyhocks, Parsley, and Foxglove.
An interesting thing to know about Biennials is that, dependant upon the climate, they can be, and sometimes are grown as Annuals.
Conditions such as rainfall, soil temperature, and location cause these plants to alter their life cycle. Generally, biennials exposed to cold temperatures early in their growth may produce seed in the first year.
Some biennial plants are also grown for their vegetable parts, and therefore harvested in the first growing season. Carrots, for instance. If carrots are left in the ground, they will flower the next growing season and produce seed. By this time, however, the vegetable will have taken on a bitter flavor. Other examples of true Biennials treated as annuals are Garlic, Cabbage, and Celery.
Are plants that live more than two years. Perennials are a bit more complicated in their classifications, as there are many factors that affect their life cycles and habits. In general, perennials can be very cold hardy, and live longer than annuals and biennials. Perennials vegetative reproductive structures allow them to return and thrive from one year to the next without seeding. These structures include bulbs, rhizomes, tubers, and crowns.
There are two groups of perennial plants; herbaceous and woody.
•Herbaceous, or deciduous perennials bloom in the growing season and die back in the fall and winter. During this time, the top foliage of the plants will perish while the rootstock remains from which the plant will bloom again in the spring. Examples of herbaceous perennials are Rhubarb, Strawberry, Asparagus, and Blueberries.
•Woody, or evergreen perennials are plants whose top growth persists throughout winter, and continues to grow larger during the spring and summer. Many trees, vines, shrubs and herbs exist within this group, including Hydrangeas, Azaleas, Peony, Apple and Pear trees, Mint, and Fennel.
Are likely the most unique and complicated classification of plants. Ephemeral plants live extremely short life cycles with specific requirements, and are broken down into three groups: Spring, Desert, and Weedy. Ephemeral plants live in less than ideal growing conditions, and have adapted to take advantage of short lasting, perfect conditions for growing. Ephemerals germinate, bloom, seed, and die all within a few weeks. The seeds they leave behind are very resilient to drastic climate changes, and lay dormant until optimal conditions once again appear.
• Spring ephemerals are, essentially, perennial plants and flowers, whose life cycles are shortened by climate. These plants typically live deep within woodlands, and their life cycle is determined by the shade of the surrounding trees. These plants sprout early in spring, and bloom and seed shortly afterward before the trees above begin to leave and shade the forest floor. With the shade, the leaves of the plants will wither and die, and the rootstalk remains as the plants become dormant until the next growing season. Examples of spring ephemerals are Ferns, Witch Hazel, and Dogwood.
• Desert ephemerals have adapted to the harsh climate of desert land. The seeds of these plants have a very low metabolism, and require little water. This enables them to survive the dry season. Once the brief wet season arrives, desert ephemerals spring up quickly, stay small, reproduce, and die, all within a few days. Cinchweed, Thale Cress, and Pale Madwort are all examples of desert ephemerals.
• Weedy ephemerals are agricultural weeds that depend on human disturbance, such as ploughing, for germination. As the soil becomes disturbed, aeration is improved, and surface light again becomes available. Weedy ephemerals grow and reproduce very quickly, and yield high amounts of seed. This group includes Hairy Bittercress, Chickweed, and Groundsel.