How Often to Water Rosemary in California

Questions people ask

How much water does rosemary need in summer?

In July, an established planting needs roughly this many gallons per square foot: 0.64 in the North-Central Coastal zone, 1.07 in the Central Valley zone, 0.2 in the South Coastal zone, 1 in the South Inland zone, 3.04 in the High and Intermediate Desert zone, 2.85 in the Low Desert zone. Figures are computed from the WUCOLS rating for Rosmarinus officinalis and each zone's reference evapotranspiration, and they are plant needs before irrigation system losses.

Does watering for rosemary change across California?

Yes. WUCOLS rates rosemary separately for each of the six California climate zones: low water in the North-Central Coastal zone, low water in the Central Valley zone, very 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.

Can you overwater rosemary?

Easily, and it is the usual way rosemary dies in California gardens. Wet soil starves the roots of air and invites root rot: needles yellow, branches brown from the base and die back one at a time, and the plant fails even though the soil feels moist. When in doubt, skip the watering and check the soil again in a few days.

How often should I water newly planted rosemary?

Keep the root ball lightly moist through the first summer while roots grow into the surrounding soil, checking whenever the surface dries. A young plant has a small root system and dries out faster than its tough looks suggest. From the second year on, switch to deep soakings with a full dry-out in between.

Is drip irrigation a good fit for rosemary?

Yes, drip suits it well. One or two emitters at the base wet the root zone slowly and keep the foliage dry, which helps prevent fungal trouble. Just do not run it on the same schedule as thirstier plants nearby: give rosemary its own valve, or cap its emitters once the plant is established and the rains return.

Do I need to water rosemary in winter in California?

In the ground, usually not. Winter rain covers the cool season across most of the state, and rosemary handles cool, dry air with ease. Winter is actually bloom time for rosemary here, so a healthy plant will be flowering, not resting. Water only during a long rainless spell, and keep checking pots since they dry faster than garden soil.

Why are my rosemary needles turning yellow or brown?

Yellow needles usually mean too much water or soil that never dries, especially on lower and inner growth. Browning that spreads from the base of a branch in damp soil is root rot, while crispy tips on a bone-dry plant mean it finally got too thirsty. Feel the soil before reaching for the hose: a thirsty rosemary looks dull and gray first.

Does watering less make rosemary taste stronger?

Within reason, yes. Rosemary grown lean and on the dry side concentrates the oils that give it flavor and fragrance, while lush, heavily watered growth comes out soft and mild. Let the soil dry between soakings, go easy on fertilizer, and harvest sprigs from firm, mature growth for the best flavor.