WateringTimesWatering plan, $19
Linum spp. & cvs., WUCOLS IV

How often to water flax in California

In July in the Central Valley, established flax in loam needs a deep watering about every 14 days: about 1.5 gallons each time for a plant 2 feet across, about 0.8 gallons a week. Flax plants are annuals, biennials and short-lived perennials, usually 6 inches to 2 feet tall, with narrow leaves and cup-shaped flowers from spring to midsummer. Blue flax, a California native of dry slopes, carries pale to dark blue flowers that open in the morning and drop by afternoon. Many kinds reseed generously, and a few turn weedy.

PerennialCalifornia nativeRated for 4 of 6 zones

How often to water flax, 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 flax 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

  • Spring soil that has dried several inches down around the plants means flax can take a drink
  • Plants drooping and sprawling in rich, moist soil point to too much water
  • Flowers fading early in a long dry spring can follow very dry soil
  • Petals dropping by afternoon is normal daily behavior, not stress

How to water it

  • Water deeply but rarely, letting the soil dry between waterings
  • Plant in full sun in light, well-drained, even sandy or rocky soil
  • Avoid rich, moist beds, where plants flop
  • Cut plants back by half after bloom to keep them tidy
  • Let some seed drop if you want new plants

Through the seasons

Water seedlings and new plants until roots grow deep, since blue flax forms a deep taproot. Established plants need little water, and rich, wet soil makes them flop, mostly in dry springs while they bloom. Flowers run from spring into midsummer, and many plants live only a few years but reseed. Flax gets a low water rating from WUCOLS on the north-central coast and the south coast, and in the Central Valley and South Inland. Neither desert zone has a WUCOLS evaluation for it.

In pots

Flax can grow in a pot of gritty, well-drained mix in full sun, where its flowers open each morning. Water when the top couple of inches are dry, until water drains out. In spring, check pots every few days while plants bloom. Never leave water in the saucer. Cut stems back by half after bloom. In summer and winter, water sparingly, since soggy soil shortens their life.

1 Your climate zone six WUCOLS zones, each from its own reference city
1.07gal per sq ft in JulyLow water use in the Central Valley zone
A year
6.84 gal per sq ft
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses
0.270.540.801.10.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.270.540.801.10.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

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

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.150.160.310.31––
Feb0.210.260.320.35––
Mar0.350.430.460.52––
Apr0.470.610.560.64––
May0.580.830.640.78––
Jun0.640.990.690.92––
Jul0.641.070.791––
Aug0.60.950.740.93––
Sep0.50.720.60.74––
Oct0.350.470.460.53––
Nov0.190.220.330.36––
Dec0.120.140.260.27––
Year4.86.846.27.37––

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 low water in the Central Valley, like flax. Plants that drink alike can share one valve and one schedule.

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 flax, 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 flax in summer?

In July, established flax in loam needs a deep watering about every 14 days in the Central Valley, about every 18 days on the south coast and about every 14 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 flax need per day?

In July in the Central Valley, established flax needs about 0.1 gallons a day for a plant 2 feet across and about 0.4 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 flax change across California?

Yes. WUCOLS rates flax separately for each of the six California climate zones: low water in the North-Central Coastal zone, low water in the Central Valley zone, low water in the South Coastal zone, low 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 do flax flowers fall off by afternoon?

Each flower opens in the morning and drops by afternoon. New buds open the next day. It is normal.

Is blue flax a California native?

Yes, blue flax grows on dry slopes and ridges from Alaska to Baja California. It suits dry gardens. Other flax species come from Europe and the Mediterranean.

Does flax reseed?

Most flax self-sow freely, and some can be weedy. Cut plants back after bloom to limit seed. Leave some seed for new plants.

Why is my flax flopping over?

Rich, moist soil makes flax droop and sprawl. Water less and skip fertilizer. Full sun helps.

Should I cut back flax?

Yes, cut the top half back after blooming. That keeps plants tidy. Skip it if you want seedlings.

More plant watering guides

SilverberryMexican FleabaneCider GumSwamp MahoganyFlooded GumRed IronbarkEvergreen EuonymusCrown of Thorns

Sources