Rosemary
Rosemary is one of the most rewarding herbs to grow at home—it's drought-tolerant, fragrant, and perfect for cooking. Whether you're growing it on a sunny kitchen windowsill or in a sheltered garden bed, the main challenge most gardeners face is overwatering. This guide covers everything you need to know to keep your rosemary thriving in temperate climates.
Watering rosemary correctly
Rosemary hates soggy soil—water only when the top 2-3 cm of soil feels dry to the touch. In spring and summer, this typically means watering every 10-14 days, but in autumn and winter, reduce to every 3-4 weeks as growth slows. Always err on the side of underwatering rather than overwatering, as root rot is the most common cause of death. Use room-temperature water and ensure pots have drainage holes.
Light requirements for rosemary
Rosemary needs full sun to thrive—aim for at least 6 hours of direct sunlight daily, preferably 8 or more. Indoors, place it on a south-facing or southwest-facing windowsill during winter to maximize light. If grown under poor light conditions, stems become leggy and the plant weakens. In summer, outdoor plants can tolerate afternoon shade in very hot regions, but indoors, the brightest spot is always best.
Soil and repotting rosemary
Use a well-draining potting mix—mix standard potting soil with perlite or coarse sand at a 1:1 ratio to improve drainage. Rosemary prefers sandy, lean soil and actually performs better in poor-quality soil than in rich compost. Repot every 2-3 years in spring, moving to a pot only slightly larger than the current one. When repotting, loosen the root ball gently and refresh the drainage layer with fresh gravel.
Temperature and humidity for rosemary
Rosemary is hardy and tolerates 5-25°C comfortably; established outdoor plants survive winters to -5°C in USDA zones 6-8. Indoors, keep it away from cold drafts and heating vents. Unlike tropical plants, rosemary doesn't need high humidity—in fact, humidity above 60% increases fungal disease risk. Ensure good air circulation around the plant, especially in winter when windows are closed.
Feeding and fertilizing rosemary
Rosemary is not a heavy feeder and often needs little fertilizer if grown in decent soil. During the growing season (March to September), feed monthly with a balanced, diluted liquid fertilizer, or apply a light dusting of slow-release granules in spring. Avoid high-nitrogen fertilizers, which encourage soft, disease-prone growth. In autumn and winter, stop feeding entirely as the plant is semi-dormant.
Common rosemary problems and solutions
Spider mites thrive on indoor rosemary in low humidity; spray leaves with water or use neem oil if infested. Powdery mildew appears in warm, humid conditions—improve air circulation and avoid overhead watering. Root rot from overwatering is fatal; if you notice wilting despite moist soil, repot into fresh, dry soil and remove any blackened roots. Prune off diseased stems with clean scissors.
Frequently asked questions
How often should I water rosemary?
Water every 10-14 days in spring and summer, only when the top 2-3 cm of soil is dry. Reduce frequency to every 3-4 weeks in autumn and winter. Rosemary prefers dry conditions, so underwatering is safer than overwatering.
Why is my rosemary turning brown and dying?
Brown stems and wilting usually indicate root rot from overwatering or poor drainage. Check the roots—if they're soft and black, repot into fresh, well-draining soil immediately and remove dead roots. Improve drainage by adding more perlite to your soil mix.
Can I grow rosemary indoors on a windowsill?
Yes, rosemary grows well indoors on a south-facing windowsill with at least 6 hours of direct sun daily. In winter, some regions may need supplemental grow light to prevent legginess. Ensure good air circulation and avoid placing it near heating vents or cold drafts.
When and how should I prune rosemary?
Prune lightly in late March as new growth begins, removing the top 5-10 cm of stems to encourage bushiness. You can harvest sprigs for cooking throughout the growing season by pinching off 5-7 cm of stem tips. Avoid heavy pruning after August as it may weaken the plant before winter.
Is rosemary toxic to pets?
No, rosemary is completely safe for cats and dogs. However, very large quantities of rosemary oil can cause stomach upset, so keep the plant where pets can't eat large amounts. The herb itself in normal cooking amounts is non-toxic.
