WateringTimesWatering plan, $19
Juniperus scopulorum spp. & cvs., WUCOLS IV

How often to water Rocky Mountain juniper in California

In July in the Central Valley, established Rocky Mountain juniper in loam needs a deep watering about every 20 days: about 55 gallons each time under a 10 foot canopy, about 19 gallons a week. Rocky Mountain juniper is a slow-growing western native conifer, narrow and pyramidal to rounded, that reaches 20 to 40 feet. Its scalelike foliage ranges from dark green to silvery blue, its reddish brown bark sheds in strips, and its waxy blue berrylike cones feed birds. It handles drought, dry sandy soil and salt spray, but not wet soil.

TreeRated for 6 of 6 zones

How often to water Rocky Mountain juniper, month by month

Your city
Canopy width
10 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 Rocky Mountain juniper 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 1.5 feet 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 under the branches, 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 canopy width

A tree with its canopy width marked across the widest branches and the circle under it shaded blue

Measure across the branches, from the tips of the outer leaves on one side to the tips on the other. A tape works, or pace it out.

Water the whole circle under the branches, shown in blue. The gallons here cover that circle.

A wider canopy means more gallons each watering, not more waterings. While the tree is young, measure again each spring.

How to tell it needs water

  • Soil dry 18 inches down past the branch tips in a young tree's first summers signals it needs a soak
  • Foliage dulling and inner growth browning during a long hot spell can indicate drought stress
  • Branches browning from the inside while the soil stays wet point to root problems from overwatering
  • Yellowing foliage near lawn sprinklers suggests the root zone stays too damp

How to water it

  • Water a young tree in a ring beyond the branch tips, keeping the trunk base dry
  • Fill the root zone slowly to a good depth, then wait until it is dry well below the surface
  • Choose an open, sunny site with sandy or rocky ground that drains quickly
  • Keep it away from lawns and other areas that are watered often
  • Taper water once the tree is established

Through the seasons

Give a young juniper a few long, slow soaks each summer while its roots reach down. After that, this western conifer gets by on rain plus an occasional deep drink. It is evergreen and grows slowly, so extra water mainly raises the risk of root trouble. Its thin, stringy bark and oily branches burn easily. Coastal and inland western gardens, from the north-central coast and Central Valley to the south coast and South Inland, hold a low water rating from WUCOLS. Both the high desert and the low desert list it as moderate water.

In pots

Rocky Mountain juniper can grow slowly in a large container for several years. Use a gritty, fast-draining mix. Water when the top few inches are dry, letting the water drain away completely. In desert heat, check every few days. Never leave water in the saucer. In winter, water only when the mix is dry. Move the pot to a sunny spot, since shade thins the foliage, and repot before roots circle the bottom.

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
0.761.52.33.00.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.761.52.33.00.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

Rocky Mountain Juniper: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.150.160.310.310.740.78
Feb0.210.260.320.350.930.93
Mar0.350.430.460.521.461.52
Apr0.470.610.560.641.891.95
May0.580.830.640.782.392.45
Jun0.640.990.690.922.852.79
Jul0.641.070.7913.042.85
Aug0.60.950.740.932.792.6
Sep0.50.720.60.742.142.08
Oct0.350.470.460.531.461.49
Nov0.190.220.330.360.930.96
Dec0.120.140.260.270.650.68
Year4.86.846.27.3721.2721.08

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

Olive TreesOlea europaea ssp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyFig TreesFicus carica ssp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyCrape MyrtleLagerstroemia spp., hybrids & cvs.low water, Central Valley1.07 gal/sq ft in JulyAloeAloe spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyPomegranate TreesPunica granatumlow water, Central Valley1.07 gal/sq ft in JulyEucalyptusEucalyptus polyanthemoslow water, Central Valley1.07 gal/sq ft in JulyPine TreesPinus canariensislow water, Central Valley1.07 gal/sq ft in JulyJunipersJuniperus spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyTexas Red OakQuercus buckleyilow water, Central Valley1.07 gal/sq ft in JulyPortuguese OakQuercus faginealow water, Central Valley1.07 gal/sq ft in JulySoapbark TreeQuillaja saponarialow water, Central Valley1.07 gal/sq ft in JulyNecklace TreeSophora affinislow water, Central Valley1.07 gal/sq ft in JulyBailey AcaciaAcacia baileyanalow water, Central Valley1.07 gal/sq ft in JulySilver WattleAcacia dealbatalow water, Central Valley1.07 gal/sq ft in JulyGreen WattleAcacia decurrenslow water, Central Valley1.07 gal/sq ft in JulySydney Golden WattleAcacia longifolialow 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 Rocky Mountain juniper, 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 Rocky Mountain juniper in summer?

In July, established Rocky Mountain juniper in loam needs a deep watering about every 20 days in the Central Valley, about every 27 days on the south coast and about every 22 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 Rocky Mountain juniper need per day?

In July in the Central Valley, established Rocky Mountain juniper needs about 2.7 gallons a day under a 10 foot canopy and about 11 gallons a day under a 20 foot canopy. Give it in deep waterings spread days apart rather than a little every day, so the whole root zone gets wet.

Does watering for Rocky Mountain juniper change across California?

Yes. WUCOLS rates Rocky Mountain juniper 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, 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.

Is Rocky Mountain juniper a fire risk?

Yes, its thin, stringy bark and volatile oils make it very susceptible to fire. Keep it out of the defensible space next to buildings. Remove dead foliage from inside the tree.

Why is my juniper browning inside?

Check for wet soil first, since it cannot tolerate wet ground. Dry, browning foliage during drought points to thirst instead. Fix drainage before adding water.

How big does Rocky Mountain juniper get?

It grows slowly to 20 to 40 feet tall and about 10 to 15 feet wide. Cultivars vary in size and color. Pick one that fits the space.

Do birds eat juniper berries?

Yes, the waxy blue berrylike cones feed birds and small mammals. No extra water is needed for them.

Does Rocky Mountain juniper handle salt?

It tolerates salt spray, drought and dry soil. It does not tolerate wet soils or high humidity. Plant it where drainage is sharp.

More plant watering guides

Fuchsia Flowering GooseberryBlack LocustCecile Brunner RoseLady Banks RoseCalifornia Wild RoseThimbleberrySalmonberryCoral Fountain

Sources