Rosemary is an aromatic evergreen shrub with leaves similar to Tsuga needles. It is native to the Mediterranean region, but is reasonably hardy in cool climates. Special cultivars like 'Arp' can withstand winter temperatures down to about −20 °C (−4 °F). It can withstand droughts, surviving a severe lack of water for lengthy periods. It is considered a potentially invasive species and its seeds are often difficult to start, with a low germination rate and relatively slow growth, but the plant can live as long as 35 years.
The plant flowers in spring and summer in temperate climates, but the plants can be in constant bloom in warm climates; flowers are white, pink, purple or deep blue. The branches are dotted with groups of 2 to 3 flowers down its length. Rosemary also has a tendency to flower outside its normal flowering season; it has been known to flower as late as early December, and as early as mid-February (in the Northern Hemisphere).