Why Is My Rosemary Dying?
Almost certainly overwatering. Rosemary is a Mediterranean plant that thrives on neglect, and the number one killer in Santa Cruz gardens is too much water, especially when summer irrigation systems treat it like a vegetable.
Rosemary evolved in rocky, dry Mediterranean hillsides. Its roots need air as much as moisture, and soggy soil causes root rot faster than almost any other condition. UC IPM identifies Phytophthora root rot as a primary cause of rosemary decline in California gardens, triggered by overwatering and poor drainage. If your rosemary is yellowing, dropping leaves, or turning brown from the base up, the roots are likely waterlogged.
The fix is simple: stop watering it so often. Established rosemary in the ground in Santa Cruz needs little to no supplemental water once it gets through its first summer. If your rosemary is on the same drip zone as your tomatoes or lettuce, that's the problem. Vegetables need consistent moisture; rosemary needs dry periods between deep soakings. Move it to its own zone or take it off the drip entirely.
Container rosemary is especially vulnerable because pots retain moisture. Use a pot with drainage holes, a fast-draining mix (cactus mix works well), and only water when the top 2 inches of soil are completely dry. Terra cotta pots dry out faster than plastic, which helps prevent overwatering.
Other possible causes: rosemary also suffers in heavy shade and in dense clay soil without amendment. But in my experience, 9 out of 10 dying rosemary plants in Santa Cruz are simply getting too much water.
This week: Check whether your rosemary is on the same irrigation zone as your vegetables. If it is, cap or remove the emitter closest to the rosemary and let the plant dry out for two weeks before watering again.
Our free Troubleshooting Guide covers common plant problems and their solutions for Santa Cruz gardens. For more on Mediterranean herb care, see our herb growing guide.
