WateringTimesWatering plan, $19
Phormium tenax, WUCOLS IV

How often to water New Zealand flax in California

In July in the Central Valley, established New Zealand 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. New Zealand flax forms a big fan of stiff, sword-like leaves, olive or bronzy green in the species and many colors in its cultivars. Tall stalks of red-orange tubular flowers rise in late spring or early summer. Established clumps look best with occasional to regular water and need good drainage.

PerennialRated for 4 of 6 zones

How often to water New Zealand 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 New Zealand 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

  • Soil dry 3 to 4 inches down at the edge of the clump means New Zealand flax is ready for water
  • Leaf tips browning during long dry spells inland can show the roots need a deeper soak
  • Ragged holes in young leaves point to snails, which often hide in the leaf fans
  • White, cottony clusters deep in the leaf bases point to mealybugs, a pest problem rather than a water one
  • Yellowing leaves and a soft base in soggy soil point to rot from poor drainage

How to water it

  • Water New Zealand flax around the base of the clump with drip, keeping water out of the leaf fans
  • Soak the root zone about a foot deep, then let the top few inches dry before watering again
  • Plant in full sun to light shade in soil with good drainage
  • Mulch around the clump but keep it off the base where the leaves emerge
  • Add emitters on the outer side of the clump as it widens over the years

Through the seasons

Water a new New Zealand flax regularly through its first summer until roots spread into the surrounding soil. Established clumps stay evergreen, and on the north-central coast they handle fairly dry conditions, though all look best with occasional to regular watering. Flower stalks rise in late spring or early summer. Planted out, it survives cold down to roughly 10 to 15 degrees. Winter rain covers the cool months on the coast and in the Central Valley in most years. WUCOLS rates New Zealand flax low water on the north-central coast and in the Central Valley. It rates moderate water on the south coast and in South Inland. WUCOLS marks it as not suited to the high desert or the low desert.

In pots

Compact forms of New Zealand flax make striking container plants. Use a heavy container with drainage holes and a well-drained mix. In summer, check 2 inches down every few days, more often inland, and water when dry. Let water drain through and empty the saucer. Potted plants are less cold hardy than plants in the ground, so shelter them if a hard freeze threatens.

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
0.631.31.92.50.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.631.31.92.50.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

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

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.150.160.780.78––
Feb0.210.260.810.87––
Mar0.350.431.151.3––
Apr0.470.611.41.61––
May0.580.831.611.95––
Jun0.640.991.742.29––
Jul0.641.071.982.51––
Aug0.60.951.862.33––
Sep0.50.721.491.86––
Oct0.350.471.151.33––
Nov0.190.220.840.9––
Dec0.120.140.650.68––
Year4.86.8415.518.41––

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 low water in the Central Valley, like New Zealand 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 New Zealand 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 New Zealand flax in summer?

In July, established New Zealand flax in loam needs a deep watering about every 14 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 New Zealand flax need per day?

In July in the Central Valley, established New Zealand 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 New Zealand flax change across California?

Yes. WUCOLS rates New Zealand 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, moderate water in the South Coastal zone, moderate water in the South Inland zone, not suited to this region 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.

What is eating holes in my New Zealand flax?

Snails often hide in the leaf fans and chew new leaves. Clear them out by hand at night or after rain. Snail damage is not a sign the plant needs water.

How do I get rid of mealybugs on New Zealand flax?

Look for white, cottony clusters at the leaf bases. The species usually survives them, but they can badly damage weaker hybrids. Cut out heavily infested leaves at the base.

How big does New Zealand flax get?

The species reaches about 6 to 10 feet tall, while dwarf cultivars such as 'Tom Thumb' stay 2 to 3 feet. A big clump has a wider root zone, so spread water over a larger area.

How cold can New Zealand flax take?

The species is cold hardy to about 10 to 15 degrees and is one of the toughest flaxes. Many colorful hybrids are less tough, so check the cultivar. Potted plants need shelter sooner.

Can you overwater New Zealand flax?

Yes. It needs good drainage, and a clump sitting in wet soil can rot at the base. Let the top few inches dry between soakings.

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Sources