WateringTimesWatering plan, $19
Equisetum spp. & cvs. (native and non-native spp.), WUCOLS IV

How often to water horsetail in California

In July in the Central Valley, established horsetail in loam needs a deep watering about every 5 days: about 1.5 gallons each time for a plant 2 feet across, about 1.9 gallons a week. Horsetails are ancient, flowerless plants with upright, jointed, mostly unbranched green stems that reproduce by spores. They spread through an aggressive network of rhizomes that can run 6 feet deep, which makes them almost impossible to remove once established. For southern coastal cities, WUCOLS advisors recommend restricting it to constructed bioswales because it can turn invasive.

PerennialCalifornia nativeRated for 3 of 6 zones

How often to water horsetail, month by month

Your city
Plant width
2 ft
Your soil

Type your city above and the days between waterings and the gallons appear here, worked out from your city's climate table. Or read the figures by climate zone further down.

Every month, on your water days. The personal plan prints this for horsetail and the rest of your yard, on the days your water supplier allows.Get the plan for $19

How this is worked out: established roots fill the top 1 foot of soil, and you water again when that soil has dried halfway. Loam soil holds about 1.5 inches of water per foot. Water the whole area the plant covers, and skip a watering after a good soaking rain.

Which soil do you have?

Dig down a few inches, take a handful of moist soil and squeeze it.

  • Sandy: gritty, falls apart when you open your hand, will not form a ball.
  • Loam: forms a soft ball that crumbles when you poke it.
  • Clay: forms a firm, sticky ball and squeezes out into a ribbon between thumb and finger.

Still not sure? Pick loam. Most garden beds sit between sand and clay.

How to measure plant width

A shrub with its width marked from one side to the other and the circle under it shaded blue

Measure across the plant, from the tips of the leaves on one side to the tips on the other.

Water the whole area the plant covers, shown in blue. The gallons here cover that area.

A wider plant means more gallons each watering, not more waterings. While it is young, measure again each spring.

How to tell it needs water

  • Soil dry 2 inches down among the stems in summer signals horsetail needs water
  • Stem tips browning and the stand thinning in heat can indicate the soil has dried
  • Stems yellowing early in late summer can follow a dry spell
  • New shoots appearing well outside the planting show the rhizomes are escaping

How to water it

  • Water the stand with a soaker or by flooding a contained basin
  • Keep the soil moist, letting only the surface dry between waterings
  • Plant only in a bioswale, a sunken container or a bed with deep solid edges
  • Choose sun or part shade where water collects
  • Remove escaping shoots at once, digging out as much rhizome as possible

Through the seasons

Keep a new planting moist while rhizomes establish. Established stands want steady moisture through the warm months. In common horsetail, spore-bearing stems appear in early spring, then green stems persist through summer until frost. Plan containment before planting, since rhizomes spread deep and wide. WUCOLS rates horsetail moderate water in the Central Valley, in South Inland and in the high desert. WUCOLS marks it as not suited to the north-central coast, the south coast or the low desert.

In pots

A container is the safest way to grow horsetail in a garden, since it keeps the rhizomes from spreading. Use a pot without cracks or open bottoms that roots could escape through, and set it on paving. Keep the mix moist, checking every day or two in summer heat. A saucer kept partly full suits it in warm weather. In winter, keep the mix damp but not flooded.

1 Your climate zone six WUCOLS zones, each from its own reference city
2.67gal per sq ft in JulyModerate water use in the Central Valley zone
A year
17.11 gal per sq ft
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses
0.761.52.33.00.4JAN0.65FEB1.09MAR1.52APR2.08MAY2.48JUN2.67JUL2.39AUG1.8SEP1.18OCT0.56NOV0.34DEC0.761.52.33.00.4JFM1.52AMJ2.67JAS1.18OND
Gallons per square foot per month, Central Valley. Peak 2.67 in Jul, 17.11 a year.

Monthly water need by climate zone

Horsetail: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan–0.4–0.780.74–
Feb–0.65–0.870.93–
Mar–1.09–1.31.46–
Apr–1.52–1.611.89–
May–2.08–1.952.39–
Jun–2.48–2.292.85–
Jul–2.67–2.513.04–
Aug–2.39–2.332.79–
Sep–1.8–1.862.14–
Oct–1.18–1.331.46–
Nov–0.56–0.90.93–
Dec–0.34–0.680.65–
Year–17.11–18.4121.27–

How this is worked out: the WUCOLS water rating for each zone times that zone’s climate for the month. A dash means WUCOLS does not rate the plant there. The figures are what the plant uses, before sprinkler losses.

Plants with the same water needs 16

Rated moderate water in the Central Valley, like horsetail. Plants that drink alike can share one valve and one schedule.

DahliasDahlia spp.moderate water, Central Valley2.67 gal/sq ft in JulyFernsNephrolepis cordifolia (SHADE IN DESERT)moderate water, Central Valley2.67 gal/sq ft in JulyDayliliesHemerocallis spp. & cvs.moderate water, Central Valley2.67 gal/sq ft in JulyBegoniasBegonia & ssp. & cvs. (shade in the desert)moderate water, Central Valley2.67 gal/sq ft in JulyCalla LiliesZantedeschia aethiopica SHADE IN DESERTmoderate water, Central Valley2.67 gal/sq ft in JulySageSalvia officinalis and cvs.moderate water, Central Valley2.67 gal/sq ft in JulyBicolor MonkshoodAconitum cammarummoderate water, Central Valley2.67 gal/sq ft in JulyGarden MonkshoodAconitum napellusmoderate water, Central Valley2.67 gal/sq ft in JulyCarpet BugleAjuga reptans (shade)moderate water, Central Valley2.67 gal/sq ft in JulySnowdrop WindflowerAnemone sylvestrismoderate water, Central Valley2.67 gal/sq ft in JulyMountain SandwortArenaria montanamoderate water, Central Valley2.67 gal/sq ft in JulySwamp MilkweedAsclepias incarnatamoderate water, Central Valley2.67 gal/sq ft in JulyOrange MilkweedAsclepias tuberosamoderate water, Central Valley2.67 gal/sq ft in JulyGreater MasterwortAstrantia majormoderate water, Central Valley2.67 gal/sq ft in JulyHardy BegoniaBegonia grandismoderate water, Central Valley2.67 gal/sq ft in JulyWax BegoniaBegonia semperflorensmoderate water, Central Valley2.67 gal/sq ft in July

Similar plants that need less water 16

Rated lower than horsetail in the Central Valley. Worth a look for a new bed or a lawn replacement.

AgapanthusAgapanthus orientalislow water, Central Valley1.07 gal/sq ft in JulyGeraniumsPelargonium x hortorum and cvs.low water, Central Valley1.07 gal/sq ft in JulySalviaSalvia greggii ssp., cvs. & hybridslow water, Central Valley1.07 gal/sq ft in JulyIrisesIris germanicalow water, Central Valley1.07 gal/sq ft in JulySucculentsEcheveria spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyRussian SagePerovskia spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyYarrowAchillea millefolium (non-native hybrids)low water, Central Valley1.07 gal/sq ft in JulyMountain AlyssumAlyssum montanumlow water, Central Valley1.07 gal/sq ft in JulySilver SageSalvia argentealow water, Central Valley1.07 gal/sq ft in JulyPurple MulleinVerbascum phoeniceumlow water, Central Valley1.07 gal/sq ft in JulySilvery YarrowAchillea clavennaelow water, Central Valley1.07 gal/sq ft in JulyFern Leaf YarrowAchillea filipendulinalow water, Central Valley1.07 gal/sq ft in JulyCalifornia Native YarrowAchillea millefolium (CA native cultivars)low water, Central Valley1.07 gal/sq ft in JulyWoolly YarrowAchillea tomentosalow water, Central Valley1.07 gal/sq ft in JulyPerennial HollyhockAlcea rosea cvs.low water, Central Valley1.07 gal/sq ft in JulyMountain Lady's MantleAlchemilla alpinalow water, Central Valley1.07 gal/sq ft in July
Minutes for your sprinklers

Turn this into minutes on your water days

Every city page has a calculator that takes horsetail, your sprinkler type and the month, and gives the minutes per water day for that supplier's schedule. Or put it in a zone of the personal watering plan and get all twelve months printed.

Questions people ask

How often should I water horsetail in summer?

In July, established horsetail in loam needs a deep watering about every 5 days in the Central Valley and about every 6 days in the South Inland zone. Sandy soil holds less water, so waterings come closer together. Clay stretches them. Check the soil before each watering and skip one after a soaking rain.

How much water does horsetail need per day?

In July in the Central Valley, established horsetail needs about 0.3 gallons a day for a plant 2 feet across and about 1.1 gallons a day for a plant 4 feet across. Give it in deep waterings spread days apart rather than a little every day, so the whole root zone gets wet.

Does watering for horsetail change across California?

Yes. WUCOLS rates horsetail separately for each of the six California climate zones: not suited to this region in the North-Central Coastal zone, moderate water in the Central Valley zone, not suited to this region in the South Coastal zone, moderate water in the South Inland zone, moderate water in the High and Intermediate Desert zone, not suited to this region in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

Is horsetail invasive?

It can be. Its rhizomes spread aggressively and can reach 6 feet deep, so it is very hard to remove. WUCOLS advisors recommend constructed bioswales only in southern coastal cities.

Is horsetail poisonous?

Common horsetail is considered toxic to livestock, especially horses. Keep it away from grazing animals. Do not let pets chew it.

How do I get rid of horsetail?

Dig out as much rhizome as possible, and expect regrowth for years. Deep roots make removal very difficult. Contain it from the start instead.

Does horsetail flower?

No, horsetail does not flower. It reproduces by spores from cones at the tips of special stems, and by rhizomes. The green stems carry out photosynthesis.

Where can I safely grow horsetail?

Grow it in a bioswale, a sealed container or a bed with deep solid edges. Wet, constructed drainage areas suit it. Keep it far from open soil beds.

More plant watering guides

English OakRed OakShumard Red OakChinese Cork OakSouthern Live OakCreeping ButtercupBloody SorrelIrish Moss

Sources