Leaves

• Leaf characteristics in plants can be very distinctive, and botanists use them as one of many features to aid in plant identification. One basic leaf variable is whether the leaves are considered to be simple or compound. Simple leaves feature a leaf stem called a petiole and a leaf blade that is one continuous surface. Simple leaves occur in a variety of shapes, but in all simple leaves, the leaf blade is one contiguous surface. Compound leaves, on the other hand, also have a leaf stem or petiole, but the leaf blade itself is divided into separate parts.
  
  An example of a simple leaf is that of the flowering dogwood tree. The dogwood tree's leaf is more or less oval with a pointed tip. An example of a compound leaf is that of the ash tree. The ash tree's leaves are usually divided into seven separate leaflets.
  
  

Stems

• Plants' stems can be just about as variable as their leaves and are very helpful in plant identification. Stems can be rounded, oval or even square. The stems may be smooth or may have projections, like corky winglike structures or thorns. Color variations like mottling or streaking can be diagnostic in plant identification.
  
  

Flowers

• Much of formal botany and plant identification is based upon flower structure, and as botanists classify plants into families, there is a strong emphasis on flower structure. It's notable that not all flowers are showy and conspicuous like those of orchids, for example; some are small and fairly nondescript, like those of blue cohosh. Either way, the details of flower structure can be critical to plant identification.
  
  

Fruit

• Another important structure that botanists used in plant identification is the fruit. What may come to mind for many of us when we think of fruit is what we find in the produce section of the grocery store. But in the broad diversity of the plant kingdom, botanists must consider many kinds of fruits--edible or not, and small or large--in plant identification.
  
  Some fruits, like those of the cherry tree, for example, have a fleshy outer part and a hard stonelike center. Others, like the fruit of the maple tree, feature seeds with wings that drift like propellers in the wind. The whole spectrum of plants' fruiting characteristics aids considerably in their identification.
  
  

Genetics

• Modern advances in genetics and DNA sequencing have, in many cases, confirmed plant identifications and classification that were based on traditional means. In some cases, genetic information has lead to some revisions of previously established identifications and classifications.