Herb Garden Plants: Rosemary

Botanical Name: Salvia rosmarinus (SAL-vee-uh rose-ma-REE-nus)

Previously known as: Rosmarinus officinalis

Family: Lamiaceae (lay-mee-AY-see-ee); mint

History and Etymology: Thriving in dry, rocky areas, rosemary is native to Africa, Europe, Western Asia, and the Mediterranean area. A member of the mint family, Lamiaceae, its genus name, Salvia, is derived from the Latin word salvo, meaning "to heal or save", referring to the medicinal properties of these plants. The species name, rosmarinus, comes from the Latin words ros, meaning "dew", and marinus, meaning "sea", a reference to its native habitat and ability to thrive in coastal areas. It has been highly valued for both culinary and medical uses. Through the years, it has been used as a symbol of remembrance, love, fidelity, and friendship, and has been customary at weddings and funerals. In ancient Egypt, it was used in the embalming procedure for pharaohs. In ancient Greece, scholars wore rosemary garlands to enhance memory and alertness.

Description: This evergreen shrub has an upright or prostrate habit. It has aromatic, opposite, stalk-less (sessile), leathery, needle-like leaves with edges that roll downward toward the underside of the leaf (revolute margins), dark green above with white fuzzy or hairy (tomentose) undersides, and are ½ to 1 ½ inches long. The square stems turn woody with age. Tiny, two-lipped, tubular flowers, ½" long, grow in short axillary clusters (racemes). The fruit is a nutlet. The essential oil imparts a pine-eucalyptus-camphor aroma.

Cultivars:

• Upright habit: for border, hedge, or accent: 'Corsican Blue', 'Gorizia', 'Majorca Pink', 'Rexford', 'Tuscan Blue'.
  • Suited for topiaries: 'Athens Blue Spire', 'Herb Cottage', 'Joyce DeBaggio', 'Shady Acres', 'Taylor Blue'.
  • Hardier (to zone 7 or 6b with protection): 'Arp', 'Athens Blue Spire', 'Madalene Hill', 'Miss Jessop's Upright'
• Prostrate habit: good for groundcovers, containers, hanging baskets, walls, and rock gardens: 'Blue Boy', 'Haifa', 'Lockwood de Forest', 'Prostratus', 'Irene'.

Plant Type and Hardiness: Tender perennial evergreen shrub; USDA Plant Hardiness Zones 8 to 10.

Height and Width: Height 2 to 6 feet; width 2 to 6 feet.

Bloom Color and Time: Blue, rarely pink or white; bloom time in winter-hardy plants is January to April; in potted plants overwintered indoors, it is spring into summer.

Light and Soil: Full sun; light, well-drained soil, sandy or gravelly, with pH 6.5 to 7.0.

Cultivation: Low viability and slow germination rates make it difficult to propagate from seed, and named cultivars do not stay true to type. It is best propagated from stem cuttings (or layering). For cuttings, take a 6-inch section of stem tip, strip lower leaves, dip the base in rooting hormone, and place in a sterile, well-aerated soilless mix, with bottom heat (70 to 75°F). Once the cuttings root (10 to 20 days), transplant out in full sun (two feet apart). Pea gravel or sandy mulch is preferred over organic mulch, which retains moisture. Prune after flowering. Where not hardy, grow as an annual or in pots taken indoors 2 to 3 weeks before the first frost date in the fall. Clay pots permit rapid drying. Place in a south-facing window in full sun or use supplemental lighting, with good air circulation. Transfer pots outside in the spring after the danger of frost. Overwintering rosemary indoors may be difficult due to low-light conditions and too little or too much water.

Companion Planting: It is said to repel cabbage moths, bean beetles, and carrot flies.

Pollinators: Its nectar-bearing flowers attract bees, butterflies, and beneficial insects.

Pests and Diseases: Outdoor plants in full sun are resistant to pests. Beneficial insects play a key role in pest control. Rosemary is prone to developing powdery mildew and root rot. Ensure adequate airflow between plants to prevent powdery mildew. Avoid overwatering to prevent root rot. Browning of tips is a sign of root rot. Thrips, aphids, whiteflies, mealy bugs, and spider mites may be a problem indoors. Though rosemary is drought-tolerant once established, it does poorly in wet or poorly drained clay soil. It is deer-tolerant.

Propagation: Stem cuttings, layering, and division

Harvesting: Cut leaves at any time during the growing season to use fresh. Prior to blossoming, harvest leaves for drying. Bundles should be hung upside down in an open area to dry. To freeze, finely slice the leaves and put them in foil, a zip-top freezer bag, or an ice cube tray with water.

Herbal Uses: Aromatic, cosmetic, culinary, decorative, and ornamental. Shampoos, conditioners, creams, lotions, fragrances, and toilette waters all include aromatic oils. The leaves are used in potpourris, wreaths, and sachets. Rosemary may be used in fiber dyeing to create a yellow-green color. It may be used fresh or dried in cooking, and due to its potent flavor, use it judiciously. Early in the cooking process, add the leaves. Use sprigs that can be removed before serving, or finely chopped fresh or dried leaves. Lamb, poultry, fish, vegetables, marinades, soups, stews, tomato sauces, eggs, cheese, butter, and vinegar are all flavors that rosemary enhances. For skewering meats and veggies while grilling, utilize its woody stems. Its attractive leaves, flowers, and forms are ornamental in the herb and vegetable garden, as hedges, borders, or topiaries. Prostrate plants are good for groundcovers, trailing from walls, hanging baskets, and containers.

Garden Notes:

• Rosemary is best propagated by cuttings. This is particularly true of named cultivars, as when grown from seed they do not remain true to type.
• It is sensitive to wet, poorly drained soils. Overwatering causes root rot, which can be deadly outdoors and especially in pots overwintered indoors. Adequate air circulation between plants will help reduce the possibility of powdery mildew.