Grass vs. Broadleaf

• Plants are monocots or dicots, which refers to the number of false leaves that first appear about the ground when the plant germinates. Grasses, corn and bamboo are examples of monocots. Almost all other plants are dicots. A general way to tell the difference is that dicots have broadleafs.
  
  

Targeting

• Different compounds in herbicides target different types of plants. The often-used 2,4-D is a natural plant growth hormone found in broadleaf plants. When sprayed over a dicot plant, it disrupts the normal growth and forces an early death. Fluazifop works similarly with grasses and other monocots.
  
  

Non-selective

• Many weedkillers are non-selective, killing any plant they touch. Homemade remedies such as vinegar and bleach solutions often fall into this category. Commercial products that are non-selective generally are used to clear out large areas of plant growth.
  
  

Improper Use

• According to Dr. Angela M. O'Callaghan from the University of Nevada, even selective weedkiller will harm all plants if overused. She recommends water spraying any plants that may have accidentally come into contact with a herbicide.