21 Nov Horsetail
Toxic to livestock
Origin: Northern hemisphere; widespread in Eurasia and North America
Habit: An upright perennial herb with sterile and fertile stems, the former to 60 cm dying back in Winter, the latter emerging in Spring to produce soft cones with millions of spores
Leaves: Inconspicuous, growing on main stems in whorls of 6–18 joined at edges to form a black-tipped sheath 5-8 mm with sharp teeth (2-3 mm) around stem
Roots: Rhizomatous, subterranean stems produce wiry roots, sometimes tubers
Dispersal: Rhizomes rather than spores most common form of spread, via soil transportation, (garden clippings/construction machinery). Spores released from fertile stems spread by wind and water need moist conditions for germination
Control: Control is difficult and prevention is critical. High silica level makes penetration by herbicide almost impossible. Ploughing and hand removal can be ineffective by the small size of rhizome or tuber from which it re-sprouts. Fire, mowing and slashing ineffective as new stems grow quickly from the rhizomes. Mulching is expensive. Small areas can be removed by digging out all plant material, including the rhizomes.