Characteristics of Horsetails

• The stem performs photosynthesis
• Accumulate silica (silicium)
• Grow in acidic soils
• Act as a diuretic
• Spring shoot – spore-bearing, summer shoot – photosynthetic
• The sexual generation is represented by male and female gametophytes
• The structure where spores are formed is called a strobilus or spore-bearing cone

Structure and Morphology

The stem is green, rigid, ribbed, and can be simple or whorled. It is jointed (composed of nodes and internodes) and usually hollow.

The leaves are scale-like, arranged in whorls along the branches, and fused into toothed brown sheaths.

Each plant produces 5-10 sporangia, which develop on the inner side of shield-like sporophylls that are grouped into a terminal cone.

Reproduction and Development

In some species, spore-bearing cones develop on specialized spring shoots that lack chlorophyll. After spore maturation, these shoots die, followed by the emergence of infertile green shoots.

When spores mature, their outer shell splits crosswise, forming four ribbon-like hygroscopic appendages, which assist in spore dispersal.

Spore Characteristics

✅ Shape – Spherical
✅ Size – 30-80 µm in diameter, relatively constant within a species
✅ Internal structure – Large nucleus surrounded by numerous chloroplasts with starch grains
✅ Outer layer – Forms spirally coiled hygroscopic bands (elaters)

The gametophytes are small and can be monoecious or dioecious.

Ecology and Practical Uses

Horsetail is a resilient plant that can survive forest fires due to its deep underground rhizomes.

Practical Applications

• Historically used for scrubbing pots and pans due to its high silica content.
• Soil acidity indicator – Its presence suggests the need for soil alkalization.
• Medicinal plant – Used in both traditional and modern medicine.
• Animal feed – Fresh horsetail is safe, but dried horsetail hay can be toxic to horses and cattle.
• Natural dye source – Combined with alum, it produces a gray-yellow dye for wool.
• Polishing material – Winter horsetail was used as a natural sandpaper for wood finishing and metal cleaning.

Medicinal Properties

Horsetail contains:

• Saponins, tannins, flavonoids
• Silicic acid, vitamin C, carotene
• Resins, malic acid, aconitic acid, oxalic acid

Medical Applications

✅ Diuretic and hemostatic agent
✅ Treatment for bladder inflammation, pleurisy, and edema
✅ External application for wounds, eczema, and skin diseases
✅ Mouthwash and nasal rinse for mucosal infections
✅ Herbal baths for children with colds

In veterinary medicine, dried horsetail powder is used for treating wounds and ulcers.

Common Horsetail Species in the U.S.

Species	Characteristics
1. Field horsetail (Equisetum arvense)	Stem slightly rough; spore-bearing shoot pinkish-brown; vegetative shoot sparsely branched with multi-angled side branches.
2. Woodland horsetail (Equisetum sylvaticum)	Soft stem; spore-bearing shoot reddish-brown, sheaths up to 25 mm long; vegetative shoot bright green with highly branched lateral branches.
3. Giant horsetail (Equisetum telmateia)	Grows up to 150 cm; unbranched or slightly branched stem with 9-10 prominent ridges and a wide central cavity; leaf sheaths with 9-20 teeth.
4. Marsh horsetail (Equisetum palustre)	Grows up to 50 cm; branched stem with 4-12 prominent ridges and a small central cavity; leaf sheaths with 4-5 teeth.