WateringTimesWatering plan, $19
Nephrolepis cordifolia (SHADE IN DESERT), WUCOLS IV

How often to water ferns in California

In July in the Central Valley, established ferns in loam need 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. Southern sword fern has a shallow root mat with wiry runners and small storage tubers. Its fronds need shade and steady moisture, while the crown needs air rather than standing water. This guidance follows that species, whose roots and watering needs do not represent every garden fern.

PerennialRated for 6 of 6 zones

How often to water ferns, 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 ferns 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 an inch or two down beside southern sword fern signals that its shallow roots need water
  • Fronds still limp the morning after heat can indicate thirst when the soil below them is dry
  • Crisp brown frond tips can accompany dryness, excess sun or salt buildup, so check the soil before watering
  • New fiddleheads stalling and shriveling during growth can indicate a dry root mat
  • Yellowing fronds or a soft, dark crown over wet soil can indicate poor drainage

How to water it

  • Water around the whole southern sword fern clump and its spreading root mat
  • Soak the top several inches, then wait until soil dries an inch or two down beside the clump
  • Use drip beneath the fronds, or water overhead in the morning so the crown dries before nightfall
  • Mulch southern sword fern with leaves or bark, keeping crowns clear and using a raised bed where water lingers
  • Place southern sword fern in shade or filtered light to protect its fronds from hot sun

Through the seasons

Keep a young southern sword fern evenly moist through its first summer as roots spread beyond the nursery ball. Established clumps draw from a wider shallow root mat but still need checks during warm-season growth. They stay evergreen in mild gardens; hard frost can kill whole fronds, with new growth returning from below ground. Winter rain can supply coastal and Central Valley beds, while desert plantings need checks through dry winter spells. WUCOLS rates southern sword fern moderate water in all six climate zones. The WUCOLS entry carries a shade note for the deserts.

In pots

Southern sword fern baskets expose a shallow root mass to drying wind around every side. Check the top inch of mix often in California summer heat, especially once roots fill the pot. Water slowly when it dries, letting excess leave the drainage holes, then empty the saucer. If dry mix sheds water immediately, soak the root mass briefly to rewet it and drain fully. In winter, shelter containers from frost and persistent rain, and reduce irrigation.

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

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

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.40.780.780.740.78
Feb0.530.650.810.870.930.93
Mar0.871.091.151.31.461.52
Apr1.181.521.41.611.891.95
May1.462.081.611.952.392.45
Jun1.612.481.742.292.852.79
Jul1.612.671.982.513.042.85
Aug1.492.391.862.332.792.6
Sep1.241.81.491.862.142.08
Oct0.871.181.151.331.461.49
Nov0.470.560.840.90.930.96
Dec0.310.340.650.680.650.68
Year1217.1115.518.4121.2721.08

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 ferns. Plants that drink alike can share one valve and one schedule.

DahliasDahlia spp.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 JulyEnglish DaisyBellis perennismoderate water, Central Valley2.67 gal/sq ft in July

Similar plants that need less water 16

Rated lower than ferns 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 ferns, 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 ferns in summer?

In July, established ferns in loam need a deep watering about every 5 days in the Central Valley, about every 7 days on the south coast 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 do ferns need per day?

In July in the Central Valley, established ferns need 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 ferns change across California?

Yes. WUCOLS rates ferns separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, moderate water in the Central Valley zone, moderate water in the South Coastal zone, moderate water in the South Inland zone, moderate water in the High and Intermediate Desert zone, moderate water in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

Can you overwater southern sword fern?

Yes. Pause irrigation when soil remains saturated and inspect the crown. Improve drainage or raise the planting as needed; continuing to water a rotting clump will not restore its fronds.

How do I check a hanging fern basket?

Learn the difference between its weight after watering and as the mix dries. A porch basket can lose moisture faster than a bed in the same shade. Misting fronds does not rewet a dry root mass.

Why are my fern fronds turning brown?

Watch where midday sun or reflected heat reaches the fronds. Salts from irrigation water or fertilizer can also burn older frond margins, particularly in containers. Flush a salty pot thoroughly and let it drain; old fronds can also brown through normal aging.

Does Epsom salt help brown fern fronds?

Do not use magnesium as the first response to browning. Check the shaded position, soil moisture and possible salt buildup first. Add nutrients only when a soil test supports doing so.

Which outdoor ferns need winter checks?

Check southern sword ferns beneath porch roofs or eaves, where rain cannot reach the roots. Desert beds also need attention during long dry gaps. Feel beneath the fronds before deciding to run irrigation.

More plant watering guides

Butterfly BushStrawberriesSageAmur MapleFernleaf MapleBox ElderNorway MapleRed Maple

Sources