Rosemary
Rosmarinus officinalis. Rosemary belongs to the Lamiaceae family, commonly known as the mint family, which also includes aromatic herbs like basil, oregano, thyme, and sage. Revered for its fragrant, needle-like leaves and culinary applications, rosemary adds a distinctive flavor to a variety of dishes. There are numerous Rosemary varieties including Tuscan Blue, Arp, and Spice Islands. Rosemary typically grows in bushy, compact forms although some varieties grow in a creeping, groundcover form.
Starting Seeds
Rosemary seeds germinate best in warm soil temperatures, with the ideal range for germination falling between 65°F (18°C) and 75°F (24°C).
Direct sowing is possible if you live in a warm climate. Otherwise start seeds indoors 10-12+ weeks prior to your last frost date. Rosemary can be slow to germinate and slow to grow as a young plant.
When to Plant Out
Rosemary should be transplanted outdoors after the last expected frost date once the weather has warmed and the soil temperatures consistently reach at least 50°F (10°C) or warmer.
Light
Full sunlight: at least 6-8 hours a day.
Space
Space plants 2-3′ apart. Be sure to check the seed packet for specifics on your variety’s size. Rosemary can grow quite large in milder climates where it may grow year round.
Temperature
Rosemary thrives in warm temperatures, with ideal daytime temperatures ranging between 70°F and 90°F (21°C to 32°C). Certain varieties of rosemary are hardy to Zone 8 or 9, surviving down to 10-20°F (-12 to -7°C) for established plants, but protection from snow may be necessary.
Water
As a Mediterranean herb, it’s accustomed to drier conditions, so overwatering can lead to root rot and other issues. Watering rosemary deeply but infrequently is usually sufficient. Allow the soil to dry out slightly between watering sessions to prevent waterlogged conditions.
Pruning
Regular pruning throughout the growing season stimulates the plant to produce more leaves and slows woody growth. Never cut back more than 1/3 of the plant at a time. Do not cut woody branches unless diseased or damaged as new growth will not occur on woody sections. If rosemary is hardy in your area, refrain from pruning/harvesting 6-8 weeks before the first frost and throughout Winter and Spring before your last frost date, so the new growth will not be damaged by frost.
Harvesting
To ensure the best flavor and continuous production of rosemary, harvest green sprigs while they are still tender.
Propagation
Rosemary is commonly propagated from seeds or through cuttings. Although seeds are readily available, we’d recommend you propagate rosemary through cuttings as seeds are slow to germinate and young plants can take up to a year to become established.
Other Considerations
Rosemary is suitable for container growing. If grown in ground in colder climates, rosemary can be saved by either potting up the plant or growing a new plant from cuttings and keeping it in a warm environment for the winter. Rosemary can do well in a windowsill for easy access in the kitchen, although older plants can grow quite large relatively quickly.