Understanding the life cycle of plants is one of the first things to consider when choosing to harvest sustainably. The life cycle of a plant includes how long a plant lives and how it reproduces itself. Most plants reproduce via seed, some plants are long-lived, others are short lived. Some plants can easily survive having flowers and fruits harvested, others are more at risk when we harvest these parts. The terms below are defined along with general comments about reproduction, propagation and suggestions as to how plants in these categories might be affected by harvesting. The following terms are meant to serve as a guideline to begin the process of inquiry into understanding our plant friends better.
Annual plants have a life cycle of one year. Annual plants do not produce wood in their stems and roots, and reproduce by seed. Plants that reproduce only via seed depend on flowers and seeds for their survival. Over-harvesting of either flowers or seeds can lead to significant declines in population.
Biennial plants typically have a two year life cycle. Plants in this category typically do not produce seeds and fruits until the second year of growth. In the first year of growth plants often produce a strong tap root, the energy stored in the root provides the energy required for flowering in the second year. Robust roots can survive the removal of the above ground plant parts, as long as enough of the root remains in the ground. This makes many biennial plants more resistant to eradication, however, they still rely on flowers and seeds to reproduce and increase population size.
Perennial plants live more than two years, sometimes hundreds or thousands of years in some cases. Plants in this category often produce woody growth, even if only in the roots. Many perennials can reproduce in multiple ways, and therefore do not rely exclusively on flowers and seeds for reproduction. Perennials are often less sensitive to harvesting, but that depends on many factors as this is a very diverse group of plants. Some other terms associated with perennials are listed below.
- Bulbous perennials are plants that grow from bulbs. Bulbs are swollen underground structures that act as storage organs for plants. Bulbs produce smaller bulblets so reproduction does not rely exclusively on seeds. Onions and garlic are examples of common bulbs that most people are familiar with. In the wild bulbous plants can be very slow growing, and can take a number of years to flower. This makes bulbs very sensitive to over-harvesting, an issue which is compounded by habitat loss.
- Woody perennials are plants that persist above ground, even in the winter. They produce wood in their stems and roots. Wood is a protective material that allows plants to resist adverse environmental conditions, and attack from pathogens and herbivores. Woody trees or shrubs can often be harvested in a sustainable way because they often produce a large volume of leaves, branches, flowers and fruits. Humans can easily propagate most trees and shrubs through making cuttings of branches. Care must always be taken, however, when harvesting branches and bark because this can put the plant at risk for infection and in some cases death.
- Herbaceous perennials are plants whose above ground parts die back and become dormant when conditions are no longer ideal for growth. Many species have woody growth in their roots. Plants in this category can be short-lived and long-lived, up to hundreds of years has been documented in some species. The above ground parts can often be harvested in a sustainable way that does not kill the plant.
- Rhizomatous plants are perennials that actively reproduce via underground root-like structures called rhizomes. It is often easy to recognize rhizomatous plants because of their dense growth habits. As these plants reproduce very successfully without flowers and seeds, it is often easy to harvest both above and below ground parts in a sustainable way. Care must always be taken, however, when disturbing the soil for removal of roots, as this can have negative impacts on the ecosystem.
- Taproot bearing perennials are plants that have a larger primary root, that often can grow deep underground. Some plants with taproots are able to regrow easily from a partial or damaged taproot. Others can be more sensitive to damage and removal of part of the root. Tap roots can also be difficult to transplant successfully. Taprooted perennials are often more reliant on flowers and seeds for reproduction.
- Seed-bearing rate refers to the rate at which flowers can be produced and pollinated, followed by the successful formation of fruits and seeds. The seed-bearing rate varies widely between plants, often adapted to the ecosystem in which they evolved. Plants that bear fruit infrequently are more sensitive to the harvesting of flowers and fruits. This should be taken into consideration when harvesting these plants.
- Spore-producing plants do not reproduce via seed. They have a complex life cycle that often involves different forms of the same plant. These plants require moisture in the environment to reproduce effectively. Some spore-producing plants are more sensitive to disturbance than others. Some, like mosses, can be very slow growing, which can make them more sensitive to habitat loss. Propagating spore-producing plants is more complicated because of the absence of seeds.
- Parasitic plants are plants that rely on parasitizing other plants for sustenance and survival. These plants may have complex relationships with microorganisms, such as mycorrhizal fungi, to facilitate their life cycle. The complexity of the life cycle of these plants is often not well-understood. Plants in this category often depend on intact ecosystems to persist in the wild. This makes ethical harvesting nearly impossible in a world where habitat loss continues to be increasing rather than decreasing.
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Join me on Sept. 22 2019 at Royal Roads University in Victoria, BC to learn more about Sustainable Wild Harvesting (click for tickets and info).