WateringTimesWatering plan, $19
Verbascum phoeniceum, WUCOLS IV

How often to water purple mullein in California

In July in the Central Valley, established purple mullein 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. Purple mullein is a rosette-forming biennial or short-lived perennial with dark green leaves at its base. In late spring and early summer it sends up tall, airy spires of saucer-shaped purple, pink or white flowers that draw bees. It wants full sun and poor, well-drained soil, and it handles dry spells better than rich, wet ground.

PerennialRated for 4 of 6 zones

How often to water purple mullein, 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 purple mullein 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 inches down beside the rosette while flower spires are rising signals that purple mullein needs a soak
  • Basal leaves going limp and dull through the morning can indicate thirst
  • Flower spires fading early with crisp, curled lower leaves can follow a long dry stretch in bloom
  • A rosette turning soft and brown at the center over damp soil points to overwatering or crown rot
  • Powdery white patches on leaves suggest mildew, which crowding and evening watering make worse

How to water it

  • Water around the rosette, not into its center, with drip or a slow hose
  • Wet the soil 6 to 8 inches deep, then let the top few inches dry before the next soak
  • Plant in poor, sandy or chalky, alkaline soil that drains fast, and skip rich amendments
  • Use gravel rather than bark mulch so the leaves resting on the ground stay dry
  • Space rosettes so air moves freely and the foliage dries quickly

Through the seasons

Keep a new purple mullein lightly moist until its rosette is growing strongly, then let the soil dry between deeper soaks. Water matters most in spring while the spires grow and open. After bloom, remove faded spikes and ease off water. The leaves are evergreen, so the rosette stays visible in winter. Winter rain covers the cool months on the coast and in the Central Valley. WUCOLS rates purple mullein low 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

Purple mullein grows well in a deep pot of gritty, fast-draining mix. The depth gives the tall spires a steady base. Check the mix an inch or two down every few days in summer and water when it is dry. Water until it drains through, then empty the saucer at once. Cut faded spires to tidy the pot. In winter, water sparingly and keep the pot out of standing rain.

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

Purple Mullein: 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 purple mullein. 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 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 JulyLady's MantleAlchemilla mollislow 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 purple mullein, 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 purple mullein in summer?

In July, established purple mullein 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 purple mullein need per day?

In July in the Central Valley, established purple mullein 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 purple mullein change across California?

Yes. WUCOLS rates purple mullein 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.

Does purple mullein come back every year?

It is a biennial or short-lived perennial, so single plants rarely last many seasons. Division in spring or root cuttings in winter keep a planting going. Do not try to extend its life with extra water.

Should I deadhead purple mullein?

Yes, remove faded flower spikes after bloom. That keeps the plant tidy. Deadheading does not change how deep to check the soil.

Why does my purple mullein have white powder on the leaves?

That is likely powdery mildew, which this plant is prone to. Water the soil, not the leaves, and give it room for air to move. Remove the worst leaves.

What is eating my purple mullein?

Caterpillars and figwort weevil both feed on it. Look under leaves and along the spires. Chewed leaves are not a sign it needs more water.

Does purple mullein need rich soil?

No, it grows best in poor, alkaline, well-drained soil in full sun. Rich soil and extra water are not what it wants. A gravel garden or dry border suits it.

More plant watering guides

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Sources