Horsetail (Equisetum arvense) is a bushy perennial with a rhizomatous stem formation. Not a non-native invasive species, but included it in this section as a problem species, which can be difficult to control. As a result, it is beneficial to take a similar approach that you would take with an invasive species, to achieve adequate control.
Horsetail is a primitive plant, related to ferns, and does not have the complex transport systems, found in higher plants, so often thrives in wet locations. To counter act it’s poor water transport system, it has evolved a thick waxy cuticle that contains a lot of silicon, to reduce water loss caused by transpiration. Both the poor transport system and the thick waxy cuticle make this plant difficult to control with a traditional herbicide strategy. It one of the few plants in the UK that glyphosate based formulations struggle to control.
Horsetails are among the earliest vascular plants. They evolved over 300 million years ago and dominated the Carboniferous Period. Their deaths and later compaction helped create the coal deposits. They are non-flowering plants that do not have seeds or fruits, but they reproduce via spores, produced by specialised structures produced early in the growing season.
Horsetail is a problem because it is difficult to control using traditional strategies, mechanical or chemical. Where conditions suit the plant, it prefers wet locations, it can dominate the vegetation almost becoming a monoculture in places. As a native plant this is not always a problem but as can be seen in the pictures above it can impede drainage and is quite capable of growing up through light weight tarmac surfaces such as footpaths, car parks or driveways.