Field horsetail

How to recognise it

Habit

Perennial with two kinds of stem: in spring brown, fertile stems, then green, sterile stems 10–50 cm tall.

Fertile stem

Light brown, unbranched, without chlorophyll, topped by a spore cone 1–4 cm long; in March–April, then dies.

Green stem

Hollow and jointed, with whorls of thin, four-angled side branches angled upwards, like a little fir tree.

Leaf

Reduced to a ring of teeth (sheath) around each joint.

Roots

Black, branching rhizomes that go several metres deep, with small tubers as food stores.

Confusion with

Marsh horsetail has no brown spring stems: the spore cone sits on top of a green stem. In field horsetail the lowest segment of a side branch is longer than the sheath on the main stem; in marsh horsetail it is shorter.

Pruning: March–September

Why grow it?

• A living fossil: a plant group that existed long before the dinosaurs.
• Fun to look at with children: the brown spore stems in March, the green ‘little fir trees’ in summer and the stems you can pull apart at the joints.
• A plant with a history: because of the silica in its stems it was once used to scour pewter and pots.
• Grows where little else will: on wet, compacted soil and on railway banks.
• An indicator of wet or compacted subsoil in your garden.

Field horsetail: where does it grow best?

• In the wild in fields, on verges, dykes, railway banks, along ditches and on waste ground.
• Moist to wet, often compacted soil: sand, loam or clay.
• Sun to partial shade.
• In the garden: rarely wanted; it turns up by itself in vegetable plots, borders and between paving.

Goes well with

• Marsh marigold: Yellow flowers in March–April at the pond edge, just when the spore stems appear.
• Water forget-me-not: Small blue flowers on the same wet soil.
• Purple loosestrife: Purple spikes in summer along a ditch.
• Yellow iris: Tall yellow flowers at the water’s edge.

Field horsetail: when and how to plant it?

1. Never plant field horsetail in a vegetable plot or border: once it is there, it is almost impossible to get rid of.
2. If you still want to show it, for instance by a pond or in a school garden, plant it in a large pot without holes, so the rhizomes cannot escape.
3. Take a piece of rhizome from a garden where it has to go, or buy a plant from a nursery specialising in native or pond plants; never take plants from a nature reserve.
4. Plant in March–April, 5–10 cm deep, in moist soil.
5. Keep the soil in the pot moist at all times and stand the pot on a paving slab, not in a border.

Care

Watering

In a pot, keep moist at all times; in open ground not needed.

Feeding

Not needed.

Control

Pull or cut green stems as soon as they appear: in the long run this exhausts the rhizome. Digging does not help.

Improving the soil

Improve drainage and reduce compaction; on loose, drier soil it does less well.

Ground cover

Dense planting or a thick mulch makes life harder for it, although it often comes through.

Tip: Pull out the green stems as soon as they appear above ground, again and again: keep it up for a few years and the rhizome is exhausted. Digging only makes more pieces.

Pruning and mowing

Pruning months: March–September.

When: From March to September, whenever new stems appear.

How:

• In March–April, remove the brown spore stems before the spores are released.
• Pull or cut the green stems at ground level; they snap easily at the joints.
• On a verge or lawn, mowing will not make it disappear, but it does keep it low.

Caution: Do not put rhizomes on the compost heap: every fragment can sprout again.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Rhizomes

Its main way of spreading: every piece of rhizome or tuber can give a new plant, even when carried in soil or potted plants.

Spores

In March–April green spores are released from the cones; they only germinate on wet, bare ground and play a smaller role.

Field horsetail: how does it get through the winter?

Hardy to −30 °C.

• The green stems die back in autumn; the rhizomes and tubers survive the winter deep in the soil.
• Fully hardy.
• In March–April the brown spore stems appear first, before the green ones.

Diseases and pests

• Spreading: Pops up everywhere from deep rhizomes. Keep pulling, for years.
• Wet, compacted soil: Field horsetail points to a wet, dense subsoil. Improve drainage and do not walk or drive on wet ground.
• Poisonous in hay: Harmful to horses and other livestock when it is in hay. Keep it out of hay meadows for animals.
• Spread with soil: Rhizome pieces travel with imported soil. Check soil and potted plants carefully.

Through the year

• March: Brown spore stems appear. Remove them before the spores are released.
• April: Spores released. First green stems.
• May: Pull green stems where it is not wanted.
• June: Green stems fully grown. Keep pulling.
• July: Pull or cut, also after mowing.
• August: Keep removing new stems.
• September: Last pulling.
• October: The stems die back.

Did you know?

• In German, field horsetail is called Zinnkraut, ‘tin herb’: because of the silica in its stems it was once used to scour pewter plates and pots.
• In the Carboniferous, relatives of horsetails grew as tall as trees, and their remains now form part of our coal.
• The spores have four little ribbons that uncoil when dry and coil up again when damp: this way they ‘hop’ about.