Spanish broom, a noxious, invasive plant

Identifying and eradicating invasive weeds in the watershed has been an important goal of the Battle Creek Watershed Conservancy. Certain invasive/noxious weeds have been identified as potential threats to the watershed, and in particular to the riparian area of Battle Creek. One of the most significant threats comes from Scotch and Spanish Broom. Mature stands of broom proliferating along the riparian corridors of Battle Creek and its tributaries pose a significant fire hazard to fish and other wildlife in the watershed and to surrounding forest lands. Aside from its potential to generate catastrophic wildfire resulting in stream sedimentation that can destroy spawning beds, broom is poisonous to livestock, unpalatable to wildlife and it is displacing native species that support the watershed's ecosystem.

Getting a Handle on Broom

Ailanthus seeds

Spanish broom and Himalayan blackberries choke the edges of waterways and displace native species.

Ailanthus seeds

Sunny, fragrant blossoms covering Spanish broom soon ripen into tens of thousands of viable seeds. This young stand is thriving below Darrow Springs in the Battle Creek watershed.

CONTROL METHODS
Manual/mechanical methods: Hand pulling of Spanish broom plants will be practical when the stand is one to four years old. When plants are small enough, pulling should be an effective mechanism of control as long as roots are removed and follow-up treatment of seedlings is done. The optimal season for pulling may be July-September when plants are already experiencing water stress (Nilsen and Karpa 1994). When plants have matured to small tree size, they are not amenable to pulling technology such as the weed wrench.

Brush hogs: Use of these machines is not likely to be effective for several reasons. Many of the sites where Spanish broom has invaded are steep slopes that may be difficult to traverse with a brush hog. The trunks of Spanish broom also rapidly increase to a size outside the range of effectiveness for this technology. Because of their twisting motion, brush hogs are more effective in reducing resprouting than is saw cutting, but resprouting should be expected following cutting by brush hog.

Saw cutting: This method would remove individuals in more mature stands when the bases of plants are too large for pulling or for brush hog removal. However, the clean cut from a saw will allow for maximum resprouting. Spanish broom has a great facility for resprouting from a saw cut even when the cut is close to the ground. Among all mechanical methods, saw cutting is the least likely to be effective in preventing resprouting. In general, manual/mechanical removal may be effective only when Spanish broom populations are very young.

Prescribed burning: After low-temperature fires Spanish broom will be able to resprout vigorously from trunk bases and stem meristems. However, a hot fire that kills all above-ground stems and burns hot and close to the ground will completely kill standing individuals and most likely remove some of the seedbank. Seeds of this species are similar in structure to those of Scotch broom (Cytisus scoparius). In heterogeneous or low-temperature fires Scotch broom seedbanks were not effectively reduced. Under similar fire conditions it is unlikely that fire will effectively reduce seedbank regeneration of Spanish broom.