How to Grow Rosemary

In this article, we share a comprehensive guide to growing rosemary at home.

Quick Guide Information

1. Common Name: Rosemary 

2. Scientific Name: Salvia rosmarinus 

3. Family: Lamiaceae

4. Life Span: Perennial

5. Time Till Harvest: 12-16 weeks from cuttings (considerably longer from seed)

6. Light Requirement: Full Sun

7. Optimum pH: 6.0 - 7.5

   
   

Rosemary is a woody, evergreen perennial native to the dry Mediterranean coastline, which explains its preference for well-drained soil, full sun, and minimal fuss once established. It's one of the longer-lived herbs in a home garden, with a single plant capable of producing for many years and eventually reaching over a metre in height and width.

Rosemary is well suited to pots and raised beds, and can be a good option in gardens with heavy clay soil that would otherwise hold too much moisture around the roots.

Propagation, Planting, and Maintenance

Rosemary germinates slowly and unreliably from seed, often taking several weeks, so most gardeners propagate from cuttings or start with a nursery seedling. Take a 10 to 15cm cutting of semi-hardwood growth, remove the lower leaves, and place it in water or directly into a free-draining potting mix. Roots typically develop within 4 to 6 weeks.

Plant rosemary in spring in a position with full sun and excellent drainage. It tolerates poor, dry soils far better than soils that stay wet, so avoid overwatering, particularly in the cooler months. A light feed of compost at planting is usually sufficient; rosemary generally doesn't need or benefit from frequent fertilising, and over-feeding can lead to soft, floppy growth with less of the concentrated flavour the plant is grown for.

Rosemary's frost tolerance varies by variety, but established plants generally handle light frosts down to around -5C to -10C without issue. Prolonged hard frost, particularly in pots where the roots are more exposed to cold, can damage or kill the plant, so potted rosemary in frost-prone areas is best moved somewhere sheltered over winter.

Rosemary requires little ongoing maintenance. Harvest tender new growth rather than cutting into old, woody stems, which are slower to regenerate. Prune from the centre of the plant periodically to maintain airflow and shape, ideally after flowering.

Growing Indoors and in Pots

Rosemary is often grown in pots, but it's one of the trickier herbs to keep happy indoors long-term, since it needs more direct sun than most windowsills provide. Start with a pot at least 30 to 40cm in diameter to allow for its woody root system, moving up to 40 to 50cm or larger as the plant matures.

Use a free-draining potting mix, ideally one formulated for succulents or Mediterranean herbs, and let the soil dry out well between waterings. If growing indoors, position it in the brightest available window and expect to supplement with a grow light over winter when natural light is weaker.

Harvesting and Storage

Rosemary can be harvested year-round from an established plant, since it's evergreen, though growth is most vigorous in the warmer months. Harvest in the morning for the best flavour, cutting sprigs of new growth rather than stripping leaves.

Rosemary dries and freezes exceptionally well, arguably better than any of the other herbs covered in this series. Hang small bunches in a warm, well-ventilated spot out of direct sun, or freeze whole sprigs in a sealed bag or container, where they'll keep for several months with little loss of flavour.

Common Problems

Root Rot - This is the most common cause of rosemary failing, almost always the result of poorly draining soil or overwatering. Plant in raised beds or pots with excellent drainage and let the soil dry out between waterings.

Powdery Mildew - Can develop in humid conditions or where plants are crowded with poor airflow. Space plants adequately and prune to improve air circulation if this becomes an issue.

Spittlebugs - These insects produce small foamy masses on stems. They are mostly a cosmetic issue and rarely cause serious damage, though a strong spray of water can dislodge them if needed.