Rosemary plant care: watering, pruning & more

With its blue flowers and aromatic foliage, rosemary brings the Mediterranean to you. Learn how to take care of this fragrant herb with our rosemary plant care tips and tricks.

Rosemary (Salvia rosmarinus) is a low-maintenance plant that needs plenty of sunshine and soil that drains well. Never overwater and only fertilise rosemary once a year in spring. Read on to find out all you need to know about rosemary plant care.

Rosemary plant care: how to water rosemary

Rosemary’s water requirements depend on the growing conditions. During the summer, when the plants are growing vigorously, they will consume more water. Water frequently but do not let the soil become waterlogged. Keep in mind that rosemary is an evergreen, so in winter, as long as temperatures do not fall below -1 °C, rosemary is alive and still using water. If it does not rain for a while, it may be necessary to water your rosemary to make sure that the soil does not dry out completely, as the plants still need some water even when it is cold outside.

Pruning rosemary

Pruning rosemary is not necessary; the plant will remain perfectly healthy without it. However, unpruned rosemary can become quite woody. Regular pruning will encourage new growth and help to maintain its shape. So, how to prune rosemary? If you want a bushier plant with multiple fresh shoots, then clip the first 5 cm off the tips to encourage branching. If you want to reduce the size of the plant, give your plants a hard prune once a year in spring to promote new growth. However, keep in mind that new growth is susceptible to frost damage, so only prune it back after the last frost has passed. Also, when giving a hard prune, cut the branches back by one third, but no more, as rosemary’s woody growth does not readily sprout new growth. When pruning, make sure your secateurs are clean to avoid transferring disease and sharp to avoid inviting disease into the plant by leaving ragged cuts.

Tip: Did you know that you can propagate rosemary from cuttings? Find out how to grow rosemary from cuttings in our other article.

Rosemary pests and diseases

While rosemary plants generally do not attract many pests, there are two noteworthy rosemary pests to be aware of:

• Rosemary beetle (Chrysolina americana): is a small, round, and colourful beetle. Both the adults and the larvae feed on the rosemary leaves and flowers. These insects are most active in late spring and summer. Pick off by hand.
• Scale insects: can occasionally be found on the underside of leaves along the midrib. Horticultural oils may have an effect on them, but in general, it is best to remove and destroy infected branches.

Fungal diseases are far more prevalent than insect pests on rosemary plants. The two most common rosemary diseases to watch out for are:

• Root rot: one of the most common problems with rosemary; is a fungal disease that thrives in wet, soggy soil environments. Not overwatering and well-draining soils will prevent most occurrences. If you do have problems with root rot, dig the plant up and trim away rotted roots with clean, sharp secateurs, leaving only healthy roots. Repot in fresh well-draining soil. Heavily amend your soil to improve drainage or move to a better location. 
• Powdery mildew: is a fungal disease caused by several different species and genera of fungi in the family Erysiphaceae. These fungi thrive in hot, humid weather. The only treatment is a strong fungicide, after which the leaves should not be consumed. It is better to trim off infected leaves and transplant your rosemary to less humid location.

Now that you know how to care for your rosemary plants, check out our in-depth article on overwintering rosemary.