PlantyBoxPot and soil
A terracotta pot at least 25-30 cm (10-12 in) wide that lets the roots breathe. Very free-draining mix: all-purpose compost with about a third grit or pumice, plus a drainage layer.
Light and position
Full sun, all day if possible. It tolerates frost down to about -5/-10 °C (14-23 °F) if the soil is dry; in cold areas keep it sheltered from wind in winter.
Watering
Sparingly: about every 5 days in summer, only when the soil is dry deep down, and much less in winter (every 2-3 weeks, or not at all if it rains). Never leave water in the saucer.
Feeding
Undemanding: a balanced feed once a month in spring and summer is plenty. Overfed rosemary loses aroma.
Harvest
Well-established plant with sprigs of at least 10 cm.
How to harvestSnip sprig tips; never take more than a third of the plant or cut into old wood.
Common problems
Almost always overwatering or poor drainage rotting the roots. Let it dry out, check drainage and empty the saucer.
Powdery mildew, encouraged by humidity and still air. Remove affected sprigs and move it somewhere sunnier and airier.
It hasn't been pruned in a while. Trim sprigs after flowering, never cutting into old, leafless wood.
FAQ
How often should I water potted rosemary?
About every 5 days in summer, only if the soil is dry deep down. Very little in winter. When in doubt, wait.
When should I prune rosemary?
After its spring flowering, cutting stems back by a third at most. You can snip tips for cooking all year.
Can rosemary survive frost?
Yes, down to about -5/-10 °C (14-23 °F) if the soil isn't wet. Cold and wet together are what kill it.
