Giant Horsetail

Equisetum telmateia

Physical Characteristics

Equisetum telmateia is a PERENNIAL growing to 2 m (6ft 7in). See above for USDA hardiness. It is hardy to UK zone 6. It is in flower in March, and the seeds ripen in April. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist soil.

Distribution

Europe, including Britain, from Sweden south and east to N. Africa and W. Asia, N.W. N. America.

Habitats

Woodland Garden Dappled Shade; Shady Edge; Cultivated Beds;

Edible Uses

Edible Parts: Shoots Stem Edible Uses: Strobil (the fertile shoots in spring) - raw or cooked[256]. The tough outer fibres are peeled off, or can be chewed and then discarded[256]. The vegetative shoots, produced from late spring onwards, were occasionally cleaned of their leaves, sheathing and branches and then eaten by native North American Indians, but only when very young and tightly compacted[256]. Root - cooked[257].

Medicinal Uses

Astringent Diuretic Poultice The plant is astringent and diuretic[257]. A decoction has been used to treat 'stoppage of urine'[257]. A poultice of the rough leaves and stems is applied to cuts and sores[257].

Known Hazards

Large quantities of the plant can be toxic. This is because it contains the enzyme thiaminase[172], a substance that can rob the body of the vitamin B complex[65]. In small quantities this enzyme will do no harm to people eating an adequate diet that is rich in vitamin B, though large quantities can cause severe health problems. The enzyme is destroyed by heat or thorough drying, so cooking the plant will remove the thiaminase[172]. The plant also contains equisetic acid - see the notes on medicinal uses for more information[213].