Trees are an essential part of any yard requiring shade; however, some trees can become invasive over time. Invasive trees can take over an entire yard, eliminating any sunlight for plants and its roots can spread under property foundations, causing severe damaging including cracking. When trees become too invasive, it is time to use an herbicide to kill the tree.
Triclopyr amine herbicides are used as brush killers and are especially potent against large shrubs such as citrus trees. According to the University of Florida Extension, "brush killers are more dilute than Garlon 3A, are packaged in small quantities (quart containers), and can be purchased at retail garden supplies. They are readily available and convenient for the small property owner to use." Typical brands that contain this potent herbicide include Garlon 3A, Renovate, Brush-B-Gone and Brush Killer.
Glyphosate herbicides are used by commercial and professional land managers. The brands that contain this herbicide include Roundup and Grass Killer Super Concentrate. This herbicide is available at all local garden centers.
Imazapyr is used for aquatic sites. This is by far the most potent herbicide available and is not recommended for home use. Imzapyr is taken up into the tree's roots and will cause severe injury or mortality. Arsenal and Habitat are the two brands that contain Imzapyr.