WateringTimesWatering plan, $19
Dryopteris erythrosora, WUCOLS IV

How often to water autumn fern in California

In July in the Central Valley, established autumn fern 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. Autumn fern is an evergreen wood fern from the woodland hillsides of Japan, China and Taiwan. New fronds unfurl coppery pink to orange-red, then turn glossy deep green by summer. It grows into a slow, arching clump in part to full shade. It wants humus-rich soil that stays evenly moist, and it suffers when the root zone dries out.

PerennialRated for 4 of 6 zones

How often to water autumn fern, 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 autumn fern 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

  • Fronds that sag and lose their gloss, over soil dry an inch or two down, mean the clump needs a deep drink
  • Crisp brown frond edges after a dry, windy spell point to a root zone that was allowed to dry out
  • Yellowing fronds over soil that stays soggy and smells sour point to drowned roots rather than thirst
  • Rows of red dots under mature fronds are spore covers, not pests, and call for no change in watering
  • Fronds fading from copper to green by summer is normal, since only new growth carries the bright color

How to water it

  • Water at the base of the clump with a slow hose or drip, wetting the soil out past the frond tips
  • Soak until the soil is moist about 8 inches down, then water again as soon as the top inch begins to dry
  • Spread 2 to 3 inches of leaf mold or shredded bark over the root zone to hold moisture and build humus
  • Plant in shade with loose, slightly acidic soil rich in organic matter, sheltered from strong wind
  • Widen the watered area as short creeping rhizomes slowly push the clump outward

Through the seasons

Keep a new autumn fern evenly moist through its first year, while its roots settle into the bed. An established clump can ride out a brief dry spell, but its soil should not be left dry. It stays evergreen where winters are mild and can lose some fronds in a cold winter. Fresh copper fronds rise in spring, and summer into early fall is when irrigation matters most. Winter rain covers the cool months on the coast and in the Central Valley. WUCOLS rates it moderate water on the north-central coast, in the Central Valley, on the south coast and in South Inland. WUCOLS has not evaluated it for the high desert or the low desert.

In pots

Autumn fern makes a good shady patio plant. Use a wide pot with drainage holes and a rich mix that holds moisture. In summer, push a finger an inch into the mix every couple of days, and water when it feels dry there. Soak until water runs from the holes, then empty the saucer. Keep the pot out of afternoon sun and hot, dry wind, which strip moisture from the fronds and the mix. Through winter rain, a pot in the open may need little or no extra water.

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
0.671.32.02.70.4JAN0.65FEB1.09MAR1.52APR2.08MAY2.48JUN2.67JUL2.39AUG1.8SEP1.18OCT0.56NOV0.34DEC0.671.32.02.70.4JFM1.52AMJ2.67JAS1.18OND
Gallons per square foot per month, Central Valley. Peak 2.67 in Jul, 17.11 a year.

Monthly water need by climate zone

Autumn Fern: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.40.780.78––
Feb0.530.650.810.87––
Mar0.871.091.151.3––
Apr1.181.521.41.61––
May1.462.081.611.95––
Jun1.612.481.742.29––
Jul1.612.671.982.51––
Aug1.492.391.862.33––
Sep1.241.81.491.86––
Oct0.871.181.151.33––
Nov0.470.560.840.9––
Dec0.310.340.650.68––
Year1217.1115.518.41––

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 autumn fern. 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 autumn fern 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 autumn fern, 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 autumn fern in summer?

In July, established autumn fern in loam needs 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 does autumn fern need per day?

In July in the Central Valley, established autumn fern 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 autumn fern change across California?

Yes. WUCOLS rates autumn fern 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, not evaluated in the High and Intermediate Desert zone, not evaluated in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

Why is my autumn fern turning brown?

Dry soil and drying wind are the usual causes of brown, crisp fronds. Check the soil an inch or two down and soak it if it is dry. Then mulch the bed and screen the clump from wind.

Can autumn fern grow in full sun?

It is grown in part shade to full shade, not full sun. In California heat, direct sun dries both the soil and the fronds quickly. Give it a spot under trees or in the shadow of a building.

What are the red dots under autumn fern fronds?

They are the bright red covers over young spore clusters, and they give the fern its species name, erythrosora. They are a normal part of the plant, not scale insects or rust. No spray or change in watering is needed.

Is autumn fern evergreen?

Yes, in mild winters it holds its fronds all year. In a cold winter it can lose some of them and behave as semi-evergreen. New fronds replace the old ones in spring.

Does autumn fern spread?

Only slowly. It forms a vase-shaped clump that widens over time by short creeping rhizomes. Expect a mature size of roughly 2 feet tall and 2 to 3 feet wide.

Does autumn fern have pest problems?

It has no serious insect or disease problems, and deer and rabbits seldom damage it. When it declines in a garden, look first at dry soil, sun and wind. Those growing conditions cause most of its trouble.

More plant watering guides

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Sources