Horsetail - Equisetum

Crop Protection - Weed Control Factsheet

Horsetail (Equisetum)

June 1996

Sixteen species of Equisetum, generally referred to as horsetail, grow in British Columbia. Two forms of these prehistoric plants grow in the province, one being the leafless scouring rush which has green stems with two black bands at the stem joints. The other, and the major troublemaker, is field horsetail (Equisetum arvense) also sometimes called mares tail, horse pipes or snake grass.

Field Horsetail

Field horsetail has two types of hollow stems which grow from deep, creeping rootstocks. The leafless or fertile stems (shown left) are light brown in colour, about one foot high with a spore bearing cone up to one and half inches long at the top. These emerge in early spring and die back soon after the spores are shed.

The sterile stems, to two feet in height, produce whorls of green, four-angled leaf-like branches which form at the joints (shown right). These begin growth as the fertile stems begin to disappear and then die back by winter. Unfortunately, unlike the stems, the rootstocks do not die back. The plants are maintained by small tubers that store food reserves and an extensive creeping rhizome system that penetrates to great depth in the soil.

Field horsetail is a problem in pastures, orchards, nurseries, hayfields, roadsides and landscaped areas particularly on poorly drained soils. It is also found in dry sites such as along railway ballast. The plants, especially when dried in hay, have long been known as a toxic concern to young horses and sheep.

Giant horsetail is similar to field horsetail but is taller, more robust and has spore-bearing cones up to four inches long.

Control

The tenacious root system of horsetail makes long term control a very difficult prospect. An integrated control approach can help alleviate the problem. Improve drainage and encourage growth of a healthy perennial grass cover. Cut or burn fertile stems prior to spore formation to reduce spread potential. Porous landscape fabrics or black plastic mulch effectively prevent horsetail growth. Sawdust or bark mulches are ineffective. Deep cultivation can be effective in the short term. Be aware that rhizomes cut into very short pieces will regenerate. Shallow cultivation and dragging the rhizomes are not advised.

Few herbicides are registered for control and their use is dependent on the situation in which horsetail grows. Casoron (dichlobenil) can be used in many woody ornamentals, tree fruits, nurseries and shelterbelts and in raspberries, cranberries and blueberries.
Amitrol-T (amitrol) controls horsetail in non-cropped areas and established shelterbelts. Various MCPA formulations will provide topgrowth control in grass pastures and cereals.
Before use of any herbicide READ THE LABEL to ensure it is registered for your cropping situation. Follow label directions!

Return to Pest Management Home