Plants share common ancestors. Over time, they have diverged from one another, although many share similar characteristics and features. Scientists classify plant species by genus, family and then major groups. The Plant family is simply a collection of plants that share characteristics grouped together. Plants that have similar flowers, reproductive structures, other characteristics and are evolutionarily related, are grouped into a plant family. Genera that share similar structures are grouped within a particular family. All plant families have Latin names that end with the suffix - aceae or eae. For example: Celastraceae, Urticaceae, or Apiaceae (celery and carrot) and Brassicaceae (cabbages and other related plants).
Some plant families, such as Orchidaceae and Asteraceae have several hundred members, others such as Ginkgoaceae have a single member. In addition to shared morphological characteristics, the family taxon provides information about evolutionary adaptations for growth conditions as well as methods for propagation. Knowing which family a plant belongs to can be useful. For example, it can help identify a new plant. If our unknown plant has the characteristics of a particular family, then we can narrow the search to find its identity. It can give us an idea of what the plant looks like. Almost anything in the Asteraceae family will look like a Daisy. Most members of the Campanulaceae family have blue flowers in a bell or star shape.
Species in the same plant family tend to have similar growth characteristics, nutrient needs, and often the same pests (pathogens, herbivores). Planting crops from different plant families on a farm and the landscape; and rotating crops of different plant families over time can interrupt the crop pest life cycles, particularly insect pests, and pathogens, and reduce yield losses due to pests. Increasing plant family diversity can also provide other agrobiodiversity benefits including, diverse seasonal growth and adaptation to weather stresses such as frosts, and drought; different soil nutrient needs, as well as producing diverse foods that provide for human nutritional needs. For example, the nightshade family includes not only the poisonous deadly nightshade, but also the humble potato and tomatoes, as well. Amaranth family includes prostrate pigweed, tumble pigweed and redroot pigweed.
Understanding how a particular species of plant relates to others within its family is important for all forms of growing and gardening because it can provide information about aspects of plant care. For instance, if we know that a particular type of plant is a member of a certain family that requires more nitrogen in the soil then we can amend our garden soil to ensure healthy growth. If we know that a particular family of plants is more susceptible to a particular type of pest, fungus, or mold then we can take preventative steps to eradicate or control those threats. In the same way, we can grow legumes (the Fabaceae family) to add nitrogen to the soil after growing plants that are heavy nitrogen users to replenish the soil’s health naturally.