Invasive Plants

Desert Broom

Do you have Desert Broom growing on your property? You can help protect our beautiful desert setting and our Natural Area Open Space (NAOS) areas by learning to identify this invader. October through January, mature Desert Broom is in bloom; the flowers are pale cream or bright white (never bright yellow). An established plant has stiff stems and leaves (like broom straws).

Homeowners are responsible for plants on their private property. This invasive weed is number one on Scottsdale’s invasive weed list, and it is on Desert Mountain’s Prohibited Plant List. Desert Broom is aggressive and grows quickly to ten feet high or more. It gets started in disturbed areas or at the base of an established plant. In Desert Mountain often it gets started near fences or other structures and in retention basins. Desert Broom burns fiercely and is a significant threat to nearby structures.

Mistletoe

Mistletoe is a parasitic flowering plant that can grow on many Palo Verde, Mesquite and Acacia trees. It grows into a dense mass of branched stems on the infected tree. About 80% of the infected trees we see around Desert Mountain are Mistletoe, while the rest are Witches Broom infestations.

Mistletoe infections are mainly spread by birds that feed on the Mistletoe berries and tap into the tree’s system for food and water. Once an infection has occurred, the root system of the Mistletoe grows within the tree branch. Left untouched, it will attain a size that will greatly weaken the tree and can kill major branches or even the entire tree. The control of Mistletoe is dificult in large areas such as the golf courses and NAOS.

The most effective way to control Mistletoe and prevent its spread is to prune out infected branches as soon as they appear. It is recommended to prune the tree branch below the point where the Mistletoe is attached. Detection and control can best be done in the fall and winter when Mistletoe is easily seen.

Witches Broom

Witches Broom is growth response to a mite infestation that causes a deformity in the natural structure of the tree, often found in Palo Verde trees. To identify Witches Broom, look for a dense mass of shoots growing from a single point resembling a broom or a bird’s nest. Witches Broom is not parasitic and has its own photosynthesis process to receive its nutrients.

Control of Witches Broom is best accomplished by properly pruning the infected branches to remove the brooms. Because the disease is caused by insects, further treatment may be needed with the application of a systemic insecticide/ miticide by a licensed pest control operator. ✺ Mistletoe

These desert broom (top right) will soon spread their seeds. (Plant at far right is a turpentine bush; it has bright yellow flowers.)

These Desert Broom (second from the top) are overtaking the native Prickly Pear and the Buckhorn Cholla.

Additional invasive plants: Mistletoe and Witches Broom (bottom right)

Witches Broom