How to Grow and Care for Rosemary

Rosemary (Salvia rosmarinus) is a fragrant and drought-tolerant perennial herb in the mint family that grows as a rounded, evergreen shrub with slender, needle-like, gray-green leaves on erect woody stems. Clusters of small, light blue to white flowers appear in spring and summer.

Plant rosemary in USDA zones 8 to 10 in the spring when temperatures stay between 55 degrees and 80 degrees or grow indoors as a houseplant. Rosemary has a moderate growth rate, reaching its mature size between 2 and 6 feet tall after several years.

This is an easy-to-grow culinary herb, favored in cooking for its earthy, citrusy, and peppery taste.

How to Plant Rosemary

When to Plant

Plant rosemary in the spring once the weather has warmed and there is no forecasted frost. Container-grown rosemary can be planted any time of the year. However, it goes dormant during the winter.

Where to Plant

Place rosemary in a sunny spot with sharp-draining soil. Good companion plants for rosemary include cruciferous vegetables (kale, cabbage, broccoli, cauliflower, Brussels sprouts), beans, carrots, and spinach.

Rosemary also grows well in containers both outdoors and indoors, as long as it can get enough sunlight. It can be slightly challenging to give rosemary enough light indoors and the plant usually won’t last as long as it does outdoors, which is usually around 10 years.

How to Plant

Space rosemary shrubs at least two to three feet apart. Plant seedlings and nursery plants at the same depth at which they were growing in their previous container. Seeds should be just barely covered with soil when planting. A support structure is typically not necessary for this shrub.

Rosemary Plant Care

Light

Rosemary likes full sun and does not tolerate any shade. This means it requires at least six hours of direct sunlight on most days. A south-facing window is ideal for indoor growth, and grow lights are often necessary to provide supplemental light.

Bring indoor plants outside in warm weather to allow them access to natural sunlight. Inadequate light can cause leggy and weak growth.

Soil

Use sandy or loamy soil for rosemary. The plant is easy to grow when planted in well-draining soil and it can get root rot in overly wet or cold soil. A slightly acidic to neutral soil pH is ideal.

Water

Rosemary is quite drought-tolerant once established, and it’s better to water sparingly rather than overwater them. Allow the top few inches of soil to dry out between waterings, and then water so that the soil is evenly moist but not soggy.

Temperature and Humidity

This shrub likes warm weather and moderate humidity levels. Most rosemary varieties can’t survive temperatures below 30 degrees, but they have good heat tolerance. They prefer temperatures between 55 degrees and 80 degrees.

High humidity can lead to rot and fungal issues, especially if there isn’t enough air circulation around the plant.

Fertilizer

Rosemary is not a heavy feeder. Mixing compost into the soil at the time of planting helps give the shrub a healthy start. Then, use a balanced liquid fertilizer, following label instructions, to promote quality growth.

Pollination

Rosemary shrubs self-pollinate and attract bees and other pollinators to the garden. Bring indoor plants outdoors in warm weather when their flowers are open to allow the blooms to naturally pollinate. 

Harvesting Rosemary

• Harvest rosemary any time of year, though it grows most actively in the spring and summer.
• Harvest by using pruners to cut off 4- to 6-inch stem tips.
  
• Dry rosemary by hanging the stems upside-down in a dry, cool, well-ventilated area, which should take a couple of weeks.
• Once the stems are dry, strip off the leaves and keep them in an airtight container in a pantry.
• Use fresh rosemary sprigs or leaves in cooking rather than drying if you prefer. The leaves are most flavorful and aromatic just before the plant blooms. 

Types of Rosemary

There are several types of rosemary to grow, including:

• ‘Arp’: This plant has light green foliage with a lemony scent, and it’s known for its cold tolerance.
• ‘Golden Rain’: This plant stays compact at two to three feet high and wide, and it features yellow markings on its foliage. 
• ‘Albus’: The trademark of this cultivar is its white flowers.
• ‘Prostratus’: This cultivar has a low, spreading growth habit at around two feet high and two to three feet wide.
  

Pruning

Prune rosemary as necessary to shape its growth after the plant is done flowering. Rosemary responds well to pruning and can also be trained into topiary shapes.

Don’t prune off more than a third of the plant at a time, as this can stress the shrub and leave it vulnerable to diseases and pests. 

Propagating Rosemary

Propagate rosemary with a cutting from a mature plant in the spring or summer. Cut a few inches of healthy new softwood growth and remove the lower leaves (keep a few at the top of the stem).

Dip the end of the cutting in rooting hormone if placing it in a moist sandy, soilless potting mix. Or, keep the cutting in a container of fresh water. Either way, place the cutting in a warm, bright spot. The cutting is ready for transplanting after roots form.

Rooting rosemary in water produces quicker but more delicate roots. Putting a cutting in sand or soilless mix takes longer but develops stronger roots that may offer the best results when transferring seedlings to the soil.

How to Grow Rosemary From Seed

Growing rosemary from seeds can be difficult, because they don't germinate easily. You'll be better off getting a seedling from the grocery store or a big-box store.

If you want to try growing rosemary from seed, you need soil, seed trays, plastic wrap (if the tray doesn't come with a cover), and ideally a heat mat and grow light.

1. Soak. Soak the rosemary seeds for 24 hours before planting to improve germination.
2. Prep the trays. Fill the seed starting trays with moist seed-starting mix.
3. Plant the seeds. Scatter the seeds on top of the seed starting trays.
4. Increase humidity and warmth. Cover the tray with plastic wrap or a plastic cover to keep humidity high. Set the tray on a heat mat or in a warm location, like on top of the fridge.
5. Maintain ideal conditions. Remove the cover occasionally to allow for some air circulation. Mist soil or bottom water to keep soil moist.
6. Remove plastic. Once the seedlings have sprouted, remove the plastic wrap and put the tray in a bright location, ideally under a grow light.
7. Transfer. Once the seedlings are around 3 inches tall, move them to individual pots, and then outdoors once the weather is warm enough.

Potting and Repotting Rosemary

Growing rosemary in pots allows you to bring it indoors during cold weather. Keep containers on a patio or deck near your kitchen for easy access.

Select a pot that’s slightly larger than the plant’s root ball. Make sure it has drainage holes. An unglazed clay container is best to allow excess soil moisture to evaporate through its walls. Rosemary needs excellent soil drainage, so use a potting mix that contains perlite, which helps keep the soil light and well-aerated.

Plan to repot every year into one container size up, using fresh potting mix. The best time to repot is in the spring. Gently loosen the plant from its previous container and situate it at the same depth in the new one, filling around the roots with soil.

Overwintering

Bring rosemary indoors well before any frost is predicted in the fall forecast. Keep it in a warm room and away from any drafts or drying air from heat vents. Continue providing it with at least six hours of sunlight per day via a bright window and/or grow light.

Back off slightly on watering in winter, though don’t allow the soil to fully dry out. Once frost is out of the forecast in the spring, the plant can go back outside.

Common Pests & Plant Diseases

High humidity and poor air circulation can result in powdery mildew—a white, powdery fungus—on rosemary plants. Powdery mildew typically won't kill a plant, but the disease will weaken it. To prevent powdery mildew, make sure the plant's soil isn't too wet, and provide good airflow.

Also, be on the lookout for aphids and spider mites, especially on indoor plants. Use an insecticidal soap as soon as you spot an infestation to prevent it from spreading.