How often to water oleander in California

In July, established oleander in loam needs a deep watering about once a month or less 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.

In July in the Central Valley, established oleander needs about 0.1 gallons a day for a plant 4 feet across and about 0.4 gallons a day for a plant 8 feet across. Give it in deep waterings spread days apart rather than a little every day, so the whole root zone gets wet.

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

Yes. This shrub shrugs off drought but sulks in soggy soil, where roots suffocate and rot. Watch for yellowing leaves dropping all over the plant while the ground stays damp, and for soft, floppy new growth. In heavy clay, let the soil dry well between soakings and consider planting on a slight mound so water drains away from the crown.

Soak a first-year oleander whenever its root zone dries, keeping it steadily moist while the roots reach outward; its famous toughness arrives only after establishment. Check the top of the root zone every few days in hot weather and soak when it dries. By the second year the plant can shift to deep, infrequent soakings, and after that it becomes one of the most drought-proof shrubs you can grow.

Yes, drip suits it well. A few emitters around the base deliver water slowly so it sinks deep, which is exactly what this deep-rooted shrub wants. As the plant grows, move or add emitters outward toward the drip line, and run the system long enough to wet the soil well below the surface rather than in short, shallow bursts.

In the ground, usually not. Oleander is evergreen but slows down in cool weather, and winter rain covers its small needs across most of the state. Water only during an unusually long dry, warm spell. Container plants are the exception and still need an occasional check, since pots dry out even in winter.

A few yellow leaves dropping from the inside of the shrub is normal shedding of old foliage. Widespread yellowing while the soil stays damp points to overwatering or poor drainage. Browning leaf edges that march across the plant branch by branch and do not recover after a deep soak can be oleander leaf scorch, a bacterial disease spread by insects that watering cannot fix. Affected branches should be pruned out, and a badly infected shrub is best replaced. Wear gloves for any pruning, keep clippings away from children, pets and livestock, and never burn oleander prunings: every part of the plant is toxic.

Not beyond a point. Oleander blooms on new growth, and moderate deep soakings through the warm season support wave after wave of flowers. Constantly wet soil does the opposite, pushing soft leafy growth and inviting root rot. If bloom is sparse, look first at sunlight, since oleander flowers best in full sun, before reaching for the hose.