Tamarisk headed for noxious weed list

County commissioners will hold a public hearing at 2:30 p.m. May 9 to consider adding tamarisk, also called saltcedar, to the list of weed species mandated for control in Larimer County.

The public hearing takes place at the Courthouse Offices Building, 200 W. Oak Street, Fort Collins.

The plant is a candidate for the noxious weed list because the continuing drought has led to a proliferation of tamarisk. Previously, the plant was held in check by steady water levels that prevented it from becoming established along shorelines of rivers, creeks, ditches and reservoirs. Inconsistent water levels, however, have allowed tamarisk to take hold and threaten to spread rapidly.

Tamarisk already has caused serious environmental problems in the Southwest, where dense stands have taken hold. Thirstier than native plants, tamarisk crowds them out, increases soil salinity and reduces biodiversity.

The tamarisk infestation in Larimer County, however, now appears relatively limited. By acting quickly, officials hope to limit its spread and commensurate damage.

Originally imported from Eurasia and Africa in the early 1800s as an ornamental plant, tamarisk are shrubs or small trees that grow in thickets to a height of 12 to 15 feet. Saltcedars become established in wet areas and sink long taproots, making them particularly difficult to eradicate.

Management of saltcedar requires a long-term commitment, according to the National Park Service. A mix of mechanical, chemical and biological measures have proven most effective.

Mechanical techniques include hand pulling, digging and root cutting, as well as use of string trimmers, axes, machetes, bulldozers, fire and flooding. Removal by hand is generally recommended for small infestations of saplings under 1-inch diameter. Root-cutting and bulldozing may be effective but are costly, labor intensive and may cause extensive damage to soils and lead to resprouting.

Fire has been used with some success, but because saltcedars are fire-adapted, they readily resprout after fire. Flooding can be used to control salt cedar if root crowns remain submerged for at least three months.

For extensive infestations of saltcedar, the NPS states that chemical control has been shown to be the most effective method. Cautious use of herbicides aids in restoration of saltcedar infested sites by allowing repopulation by native plant species.

Fifteen insects also are being investigated as potential biological control agents for saltcedar, according to the NPS.

At its fall meeting, the Larimer County Weed District Advisory Board agreed that tamarisk should be added to the list of noxious weed species. This decision is the result of several meetings held to acquire public input on the tamarisk situation.

More information on tamarisk (Tamarix parviflora and Tamarix ramosissima) is available at the Larimer County Weed District web page www.larimer.org/weeds/tamarix.htm.

Information is also available by calling the county's weed district office at 498-5779.