Advice
RHS Help & Advice
Field horsetail (mare's tail) control
One of the most dreaded weeds, established field horsetail has roots that are usually too deep to dig out. Repeated destruction of foliage will eventually weaken the plant; alternatively, treat it with an approved weedkiller but it is likely that more than one application will be necessary
Identifying horsetail
Equisetum arvense (field horsetail) has creeping rhizomes, which may reach 2m (6.5ft) below the soil surface. There are two types of shoots: in late spring light brown, fertile stems 20-50cm (10-20in) appear, terminating in cone-like spore-producing structures. Later, sterile green shoots develop into (60cm/2ft) fir-tree-like plants.
Chemical control
Applied in early spring, dichlobenil (Casoron G4 Weed Barrier) can inhibit new shoots. Do not use near herbaceous plants, bulbs or crops. Apply glyphosate (Roundup Tree Stump & Rootkiller or Deep Root Ultra Tree Stump & Weedkiller) in late summer when weed growth is strong. Before spraying, trample or drag a rake across plants to bruise the cuticle which assists herbicide penetration. Glufosinate ammonium with fatty acids (Advanced Weedkiller Ready to Use for Beds & Borders) can kill horsetail shoots. The fatty acids are said to dissolve the plant’s outer cuticle, aiding penetration. Treat regrowth promptly.
Persistent clumps can be spot treated with aerosol formulations (Advanced Glyphosate Spot Weeder for Beds & Borders) or ready-to-use sprays.. Further applications may be required later in the season or the following year. Apply with care as these herbicides are not selective; always use according to the manufacturer’s instructions.
Cultural control
Rhizomes can be forked out of upper soil layers, but deeper roots often will regrow from small pieces. Shallow, occasional weeding is not effective and may spread the problem. By regularly removing plants as soon as new shoots appear above ground, infestations can be substantially reduced in a few years. Horsetail sometimes appears in new lawns, but will not persist if the grass is regularly mown.
William Denne