Selecting a Planting Site
Rosemary grows best in a sunny spot that has soil with sharp drainage. Make sure no taller trees or shrubs in the area are so close that they will shade the rosemary. Rosemary also grows well in containers both outdoors and indoors, as long as it can get enough light.
Spacing, Depth, and Support
Space rosemary shrubs at least 2 to 3 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 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
A well-draining sandy or loamy soil is best for rosemary. It doesn’t grow well in heavy clay and wet soils. A slightly acidic to neutral soil pH is ideal (6.0 to 7.0).
Water
Rosemary shrubs have good drought tolerance once they are mature, and it’s better to underwater 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. Moreover, 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 can help to give the shrub a healthy start. Then, using a balanced liquid fertilizer, following label instructions, will continue 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.
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 2 to 3 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 2 feet high and 2 to 3 feet wide.
Rosemary vs. Lavender
Rosemary and lavender are similar in appearance. Both are shrublike with woody stems, and they feature aromatic leaves that are long and thin. However, rosemary plants generally grow larger than lavender. Rosemary blooms form among the foliage while lavender blooms rise above the foliage on flower spikes. And lavender has a lighter and more floral taste and aroma than rosemary.
Harvesting Rosemary
Rosemary can be harvested at almost any time of year, though spring and summer are when it grows most actively. And the leaves are most flavorful and aromatic just before the plant blooms. To harvest, use pruners to cut off 4- to 6-inch stem tips. Use fresh rosemary sprigs or leaves in cooking as you like. Or hang the stems upside-down in a dry, cool, well-ventilated area for drying, 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.
How to Grow Rosemary in Pots
Growing rosemary in pots allows you to bring it indoors during cold weather. You also can keep containers on a patio or deck near your kitchen for easy access while cooking. 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.
Pruning
Prune rosemary as necessary to shape its growth after the plant is done flowering. Rosemary responds well to pruning and can be trained into topiary shapes. But 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.
How to Grow Rosemary From Cuttings
If you would like to propagate your own rosemary plant, the best option is to start with a cutting. Not only is this an inexpensive way to get a new plant but taking cuttings from a mature plant can help to promote more branching and bushier growth. The best time to take a cutting is in the spring or summer. Here’s how:
How to Grow Rosemary From Seed
Growing rosemary from seeds can be difficult because they don’t germinate easily and they often do not grow true to their parent plant. If you wish to try growing rosemary from seed, plant several more seeds than the number of plants you hope to grow. Start seeds around three months prior to your area’s projected last frost date in the spring. Take these steps:
Potting and Repotting Rosemary
Use a light, well-draining potting mix when growing rosemary in a container. 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 it 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. And slightly back off on watering, 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 and 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 a few feet of space around it for 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.
