Basic Methods

• While flower structure and fruits are often used to identify different families of plants, as pointed out by Alwin Gentry in his Field Guide to the Families and Genera of Woody Plants of Northwest South America and Ecuador, "Many...plants are suprisingly easy to identify to family, even in sterile condition." You can frequently determine what family a plant belongs to by examining plant structure and habitat.
  
  

Leaf Structure

• A forestry engineer shows students how to identify plant families based on leaf characteristics.
  
  Leaves can be divided into various categories based on their type, shape, arrangement, margins, texture, color, odor, taste and other features. The two basic leaf types are: simple--a single leaf attached to the stalk by means of a branchlet called a petiole--and compound. Compound leaves consist of various leaflets that are separate at the base. Depending on how many leaflets there are and the manner in which they are arranged, different types of compound leaves are referred to by a number of descriptive terms such as palmate, pinnate and bipinnate.
  
  Although leaf arrangements vary from species to species, in many instances they can be a good way to determine whether or not a plant belongs to a particular family. The basic leaf arrangements are: opposite (leaves that grow opposite each other with respect to the main stalk or branch), alternate (this type of leaf placement differs from its counterpart in that the leaves grow at different intervals on either side of the stalk) and whorled (this term refers to plants that have several leaves all growing out of the same place on the stalk or branch).
  
  While leaf characteristics such as shape, margin and venation can also be helpful in making family identifications, odor can be particularly helpful, especially in the avocado (Lauracea) and eucalyptus (Myrtaceae) families. Annonaceae, the soursop family, is also often identified by its distinctive odor.
  
  The best way to determine a family using odor is to crush leaves (or pieces of bark) in your hand before smelling them. A word to the wise: some odors can be surprisingly deceptive and may even lead to false identifications. That's why it's usually a good idea to look for at least two or three characteristics ( i.e., leaf arrangement and leaf type and odor) before making a positive identification.
  
  

Trunk and Branches

• Peeling bark is typical among members of the eucalyptus family.
  
  Some families of plants and trees exhibit features that make them easy to identify. While botanists tend to examine fruits and leaf structure, forestry engineers and loggers often prefer to identify a tree by its bark. Things to look for include: trunk (Is the plant or tree tall, short, slender or thick? Does it's trunk or stalk divide into several segments or is it straight?), bark (species such as those belonging to the Eucalyptus (Myrtaceae) family tend to have extremely distinctive bark), branches (the number of branches and the manner in which they grow can often serve as helpful clues), spines or thorns (the presence or absence of spines or thorns may can also be useful in determining what family a plant belongs to) and sap (while some plant families produce a sticky latex, others have clear resin or colored sap).
  
  

Habitat

• Neotropical rainforests contain a wide variety of plant families
  
  In order to determine which family you are dealing with, it is important to consider the habitat. Some families are only present in certain areas, so make sure to use a field guide that is specific to your location.
  
  

Other Characteristics

• Ear pod trees have a distinctive umbrella-like shape and shed their leaves.
  
  Features such as height, growth pattern, as well as the quantity and density of foliage, should also be taken into account. In addition, it's important to consider whether the plant you are dealing with is evergreen or deciduous.