Growing Rosemary Plants: Rosemary Plant Care

Rosemary plants are usually propagated by cuttings, as it can be tricky getting evergreen rosemary seeds to germinate. Successfully growing rosemary plants from seeds comes only when the seeds are very fresh and when planted in optimum growing conditions.

How to Grow and Care for Rosemary

This aromatic herb can grow in pots or in your garden with these simple methods.

Marie Iannotti is a life-long gardener and a veteran Master Gardener with nearly three decades of experience. She’s also an author of three gardening books, a plant photographer, public speaker, and a former Cornell Cooperative Extension Horticulture Educator. Marie’s garden writing has been featured in newspapers and magazines nationwide and she has been interviewed for Martha Stewart Radio, National Public Radio, and numerous articles.

Julie Thompson-Adolf is a Master Gardener and author with over 30 years of experience in year-round organic gardening; seed starting, growing heirlooms, and sustainable farming.

The rosemary plant (Salvia rosmarinus) is a fragrant herb that grows as a perennial, rounded, evergreen shrub. It features slender, needle-like, gray-green leaves on erect woody stems. Clusters of small, light blue to white flowers appear typically in the late spring to early summer, though it can bloom at other points of the year as well. Plant rosemary in the spring after any threat of frost has passed. You can also grow rosemary as a houseplant. Keeping it alive indoors is a bit more challenging, however, and it usually won’t last as long as an outdoor plant, which can live for up to ten years. Rosemary takes a while to get established. It has a moderate growth rate, and it only reaches its mature size after several years. In ideal conditions, however, it can grow up to 12 inches in one summer.

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.

Propagating Rosemary

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:

1. Cut a piece of healthy stem that’s a few inches long. Choose new softwood growth for best results.
2. Remove the leaves on the lower portion of the stem, leaving at least five leaves.
3. Dip the cut end in rooting hormone.
4. Plant the cutting in a moist soilless potting mix in a small container that has drainage holes.
5. Place the container in a warm spot that has bright, indirect light. Mist the cutting daily, and make sure the growing medium doesn’t dry out.
6. In about two to three weeks, gently tug on the stem to check for roots. If you feel resistance, you’ll know roots have developed. After that, the cutting is ready for transplanting.

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:

1. Soak the rosemary seeds for 24 hours before planting, which improves germination.
2. Scatter the seeds in a tray filled with moist seed-starting mix, just lightly covering them with the mix.
3. Cover the tray with plastic wrap to trap moisture, and make sure the mix doesn’t dry out.
4. Place the tray on a heat mat to keep the soil between 80 degrees and 90 degrees Fahrenheit.
5. As soon as seedlings appear, remove the plastic wrap, and place the tray in bright light.
6. Once seedlings are around 3 inches high, move them to individual pots or outdoors if the weather is warm.

Potting and Repotting Rosemary

The soil for rosemary needs excellent drainages so use a potting mix that contains perlite, which helps to keep the soil light, well-aerated, and well-draining. 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.

Growing Rosemary Plants: Rosemary Plant Care

Evergreen rosemary is an attractive evergreen shrub with needle-like leaves and brilliant blue flowers. The flowers of evergreen rosemary persist through spring and summer, filling the air with a nice piney fragrance. This beautiful herb, mostly used for seasoning dishes, is also commonly used as ornamental plantings in the landscape.

The scientific name for rosemary plant is Rosmarinus officinalis, which translates to “mist of the sea,” as its gray-green foliage is thought to resemble mist against the sea cliffs of the Mediterranean, where the plant originates.

Evergreen Rosemary Plant Care

Rosemary plant care is easy. When growing rosemary plants, provide them with well-drained, sandy soil and at least six to eight hours of sunlight. These plants thrive in warm, humid environments and cannot take extremely cold temperatures. Since rosemary cannot withstand winters below 30 degrees F. (-1 C.), it’s often better when growing rosemary plants to put them in containers, which can be placed in the ground and easily moved indoors during winter.

Rosemary prefers to remain somewhat on the dry side; therefore, terra cotta pots are a good choice when selecting suitable containers. These pots allow the plant to dry out faster. Thoroughly water rosemary plants when the soil is dry to the touch but allow the plants to dry out between watering intervals. Even indoors, rosemary plants will require lots of light, at least six hours, so place the plant in a suitable location free of drafts.

Trimming Rosemary

Pruning rosemary will help make a bushier plant. Most herbs thrive on being trimmed every now and then, especially those used for flavorings. Snip sprigs just as you would when cutting back a houseplant, trimming rosemary once blooming has ceased. The general rule for trimming rosemary is not to take more than one-third of the plant at any time and make cuts just above a leaf joint. These can then be dried like any other herb by hanging tied bundles upside down in a cool, dry place.

Evergreen Rosemary Propagation

Rosemary plants are usually propagated by cuttings, as it can be tricky getting evergreen rosemary seeds to germinate. Successfully growing rosemary plants from seeds comes only when the seeds are very fresh and when planted in optimum growing conditions.

Start new rosemary plants with cuttings from existing evergreen plants. Cut stems that are about 2 inches (5 cm.) long and remove leaves on the bottom two-thirds of the cutting. Place the cuttings in a mixture of perlite and peat moss, spraying with water until roots begin to grow. Once roots have developed, you can plant the cuttings as you would with any rosemary plant.

Rosemary plants are prone to becoming root bound and should be repotted at least once a year. Yellowing of the lower foliage is an early indication that it’s time to repot.

Watch A Video About Growing Rosemary: