The narrow leaves and small, blue flowers of rosemary species may cause you to wonder what would create such genetic adaptations. Rosemary originates in the Mediterranean, where an arid environment forced the plant to adapt to somewhat harsh conditions. The flowers, leaves and other attributes of the rosemary plant are a result of these specific environmental adaptations.
Like many plants, rosemary developed its flowers in a way that would attract pollinators. The blue color and aromatic scent of rosemary evolved to attract bees, butterflies and other insects to the flower. These pollinators play a central role in the plant's reproduction. Scientists know that the size of the flowers among rosemary species is directly affected by their native environmental conditions. Smaller flowers developed among many species because of the need for resource conservation in an arid environment. Though pollinators might notice larger flowers better, rosemary plants compromised by creating smaller ones rather than die out. The result is that the rosemary plant's flowers are minute compared with many other plants.
Rosemary plants have many adaptations that help the plant survive hot, dry weather. The leaves exhibit a thick and waxy or leathery texture and can store moisture. Many species have grey leaves that reflect sunlight and keep them cool. Rosemary leaves lack the wide surface area that many plants exhibit in their leaves, so they resist water loss. It is also believed that the aromatic oils within rosemary help the plant retain water. Their deep roots are adept at absorbing moisture in the soil. The strong, aromatic aroma of rosemary leaves also helps the plant repel destructive insects and pests.
A good rule for growing any plant, including rosemary, is to create an environment like the one where the plant evolved. Rosemary does not require much water, and it prefers somewhat dry soil, just like that of the environment it came from. Alkaline soil of any type is best. It does well in a drought-resistant landscape and is a hardy and vigorous plant. Provide rosemary occasional water, but do not overwater. Rosemary can be susceptible to root rot due to the plant's proficiency in retaining water, so always provide well-draining soil and a full sun location for the best growing results.
Rosemary can be grown in an herb garden or used as a full-size border or hedge. If you grow rosemary for culinary purposes, you can harvest it whenever the leaves are large enough. Use the thin, waxy leaves in breads, pastas or soups to add strong herbal flavor.